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Zagazig University Faculty of Veterinary Medicine Dep. of Bacteriology, Mycology and Immunology


* *

★ ★ * *


Dr. Gamal A. Elmowalid

Immunolog y

Science concern with studying:

1- Protection against infection 2- Organization and homing of immune cells in immune organs 3- Mechanisms of secretion of immunological product as: Antibodies & Cytokines And their roles in ☻Protection ☻Diagnosis of infectious agents ☻Designing vaccines

Immunity Term immunity is derived from Latin word (immunis) = exempt from charges Immunity or resistance is a state of protection from infectious diseases through its inherited and acquired protection This immunity is conferred by immune system Immune system Is complicated collection of: Cells




That act in a very complicated manner to provide protection to the host

The main aims of immune system 1- protect body against infectious agent 2- Defense against non-infectious agents as: cancer Transplanted tissues 3- Confer immunity -- limit damage by infectious agents 4- induce memory response (successful immune response on re- infection) 5- Differentiate self from non-self



A. Specific cell B- lymphocyte T- lymphocyte Interact with each M.O by special way Characters of specific cells: 1- Diversity ‫تنتشر وتتوسع مع ملييين‬ 2- Specificity ‫ في نفس‬M.Os ‫ال‬ ‫الوقت‬ 3- Memory response 4- Differentiate between self &non-self

B. Non-specific cell Granulocyte


Neutrophils Basophil Esinophil

Monocyte Macrophages Denderitic cells

Interact with any M.O by the same way


Lymphoid organs and tissues ‫هام جدا‬

Classified according to function to: Primary



Primary lymphoid organs.

Secondary lymphoid organs

[ Central ]

[ Peripheral }

the sites where lymphocytes

originate and mature 1- bone marrow, bone

marrow equivalent (bursa of Fabricius in birds)

The sites in which the

immune response develops 1- lymph nodes 2- spleen 3- tonsils

2- the thymus Its role

Its role

1- Hematopoiesis and

1- Trapping of antigen


‫بيئة محيطة مناسبة‬

2- Provide appropriate

microenvironments for the development and maturation of lymphocytes.

3- Enable lymphocytes to

recognize foreign antigen. antigen

4- Enable lymphocytes to

distinguish self from non self.

and particulate

substances from the blood and lymphatic fluid.

2- Processing and

presentation of the ‫تعاون‬ trapped antigen to the lymphocytes.

3- Sites of immune cells interaction and cooperation

GALT = Gut-associated lymphoid tissue

MALT Mucosa associated lymphoid tissue

BALT = Bronchus-associated lymphoid tissue

SMLT = Sub -mucosal lymphoid

tissues of genitourinary tract

Ontogeny of the immune cells ( Hematopoiesis )

☯ Is a continuous process to maintains a steady state in which :

the production of mature blood cells


their loss

(principally from aging)

☯ Human being must produce :

3.7 x1011 WBCs / day.

☯ Hematopoiesis is regulated by complex mechanisms include: 1. Control of the levels and types of cytokines produced by stromal cells of B.M. B.M 2. The production of cytokines by other cell types, such as activated T cells and macrophage . 3. The regulation of the expression of receptors for cytokines in stem cells and progenitor cells. 4. The removal of some cells by controlled cell death .

Hematopoietic Hematopoietic stem stem cell cell


All All blood blood cells cells arise arise from from hematopoietic hematopoietic stem stem cell cell (HSC) (HSC) which which originates originates from from the the yolk yolk sac sac and and foetal foetal liver liver by by process process called called hematopoiesis hematopoiesis


HSC HSC characterizes characterizes by: by: 1. 1. 2. 2. 3. 3.

Their Their ability ability to to differentiate differentiate into into other other cell cell types types Their Their capacity capacity to to make make self-renewal. self-renewal. Their Their levels levels are are maintained maintained by by cell cell division division under under the the control control of of cytokines cytokines

☯ Hematopoiesis occurs in the bone marrow producing:

erythrocytes, platelets, monocytes, granulocytes, and B cells, precursors for T cells, natural killer (NK) cells, dendritic cells, and mast cells

☯ Two cytokines play a central role in hematopoiesis: IL 3 + colony-stimulating factors

myeloid cell development


IL 7 produced by stromal cells in the B.M

lymphoid cell development

Other cytokines are also involved in the process of hematopoiesis as IL-1, IL-2, IL-6

â˜Ż Then mature WBCs ( leukocytes) carried within the blood and lymph from primary lymphoid organs to secondary lymphoid organs then to sites of infection.

Thymu Thymuss

The thymus is the site of T-cell development and maturation

◘ ◘

Situated above the heart

Each lobule is organized into two compartments

It is a flat, bilobed organ ,each lobe is surrounded by a capsule and is divided into lobules, which are separated from each other by strands of connective tissue called trabeculae 1. the outer compartment (cortex) , is densely packed with thymocytes 2. the inner compartment (medulla) , is sparsely populated with thymocytes

Thymus are crisscrossed by a stromal-cell network composed of : 1. Macrophages 2. Dendritic cells 3. Epithelial cells  Some cortical epithelial cells have long interconnecting cytoplasmic extensions that form a network and interact with numerous thymocytes 4. Nurse cells  One of thymic epithelial cells in the outer cortex  have long membrane extensions that surround as many as 50 thymocytes, forming large multicellular complexes These cells make up the framework of the organ and contribute to the growth and maturation of thymocytes



1. Thymic hormons

Mature T - Cells 2. Thymocyte growth factors 3. Cellular matrix specially nurse cells


T cell Maturation With lymph or blood

1. Thymocyte leave B.M Thymus 2. Thymocyte enter the cortex of thymus . 3 Thymocy te

1. Thymic hormons 2. Thymocyte growth factors 3. Cellular matrix specially nurse cells

Migrate to

Mature T Cells Circulate

4. Interaction of T – Cells with other thymus cells -Induce the expression of T-cell receptorts , CD3 complex , CD4 , CD8 5. Clarified of these cells by stromal cells [ Macrophages , Denteritic cells ] which contain on it’s surface MHC class I , II ( important in recognition of T – cells( 6. T- lymphocytes selection A. Positive Positive selection selection A.

◘ takes place in the cortical region of the thymus ◘ interaction of thymocytes with cortical epithelial cells

The Thymocyte whose receptors able to bind to MHC of epithelial cell will receive a protective signal that prevents them from undergoing cell death

Thymocyte whose receptors are not able to bind MHC molecules would not interact with the thymic epithelial cells so, not receive the protective signal -- death by apoptosis

B. Negative Negative Selection Selection B.

Ensures Self-Tolerance


thymocytes that survive positive selection comprises:

cells with lowaffinity receptors for MHC molecules

Survive & circulate

other cells with high -affinity receptors. undergo negative selection dendritic cells and macrophages bearing class I and class II MHC molecules interact with thymocytes bearing highaffinity receptors Negative selected cells will undergo death by apoptosis


Apoptosi Cell death ( ( Programming s

1. Shrinkage of cells 2. Fragmentation of nucleus


3. Cell membrane blebbing 4. Cell membrane , Cytoskeleton allow intact pieces of the cell to separate 5. recognized and phagocytosed by macrophages















The relation relation between between thymus thymus and and The development of of immune immune response response development A. Neonatal thymectomy

B. Adult thymectomy

1.Drop in the levels of circulating lymphocytes

1.Circulating lymphocytes will decline progressively. progressively

2.Increase animal susceptibility to infection with subsequent immunodeficiency

2.Due to presence of lymphocytes reservoir in other body tissues, this effect will replenished over the time

3.Inability of animal to mount cell-mediated immune response

3.The ability to mount an immune response will gradually decrease. decrease

4.Animal can not reject tissue grafts

4.Delay in tissue graft rejection

5.The antibody response to T cell-dependent antigen is significantly inhibited. inhibited

5.Immune response against thymus-dependent antigens will be greatly affected 6.Continuous exposure to viral and parasitic infection (intracellular pathogens)

I-Classes I-Classes of of immunity immunity Non-specific immunity

‫هام جدا‬

Specific immunity

Innate or Inherited 1. Inherited

Adaptive or Acquired 1. Acquired

2. Front Line of host Defense

2. Consequent line of host defense

3. Immediate to early response (minutes – hours)

3. Immediate to late response

4. Not specific

4. specific

5. No memory response

5. Memory response

6. No anamnesis ‫( تذكر‬no magnitude 6. Anamnesis in response) 7. Do not rely on clonal expansion of Ag-specific lymphocytes

7. Rely on clonal expansion

8. Recognizes broad classes of pathogens

8. Recognize Ag with MHC

9. Can discriminate ‫ تميز‬between self and non-self

9. Only if MHC is present

10. Example :

10. Example :

✰ Fixed Defenses

Epithelium Phagocytes

‫يتكل علي‬


✰ T- lymphocyte

Cell-mediated response

✰ Complement System

Cascade of plasma proteins that opsonize pathogens and induce series of inflammatory responses ✰ Receptors

✰ B- lymphocyte

Humoral response

Recognize broad range of 2 pathogens classes work together in orchestrated manner to 1. Eliminate pathogens 2. Protect against foreign invaders.

Differencebetween betweenBB&&TTlymphocyte lymphocyte Difference T - lymphocyte

B - lymphocyte

Specific cellular immunity

Specific humoral immunity

Complete its maturation in thymus

Its maturation and development in bone marrow (mammals) or bursa of fabricious (birds )

At periphery of lymph follicles

In centre of lymph follicles

Smaller ( 6-8 Îź )

Medium(9-10)or large (12-15)

Survive longer

Survive less than T-cell

Don’t divide at the site of inflammation

Divided to give small lymphocytes which developed into large lymphocytes

Function : Secrete inflammatory cytokines which differentiate TLC into : Effector cells Memory cell Both controlling: 1. Infected cells 2. Intracellular pathogen 3. Viral infection 4. Tumor control

Function : 1. Produce Ab to over come infection 2. Memory response

II - Classes of immunity

.A Cellular Specific

T - Cells


Phagocytic cells

.B Specific


Humoral ( Fluid) Non-specific

Complement IFN

T- helper


T- cytotoxic T- suppressor T- delayed hypersensetivity A. A.NonNon- specific specific innate innate immunity immunity Basic inherited resistance to infectious diseases that individual or species possesses Represented by barriers: 1. Anatomical barriers 2. Biological barriers 3. Physiological barriers 4. Chemical mediators 5. Mechanical barriers (physical) 6. Inflammatory barriers 7. Phagocytic barriers

1.Anatomical 1.Anatomical barriers barriers

 the first line of defense against pathogens and infection  prevent the entry of pathogens and their spread in hosts Skin - 1 1 -Has a unique histological structure that enables it to be the first barrier of defense together with mucous membranes 2 - Prevents the penetration of most pathogens 3 - Inhibits most bacterial growth via its unique structure The epidermis thin layer 

The dermis thicker layer

Contains several layers

Composed of C.T ,B.V, hair

epithelial cells

and sweat glands

of tightly packed

follicles, sebaceous glands,

 No blood vessels Confer protection

Prevent pathogens invasion

1. Its continuous

1. Sebaceous glands-glands- sebum

through :

sloughing off and is


(fatty acids + lactic acid )

constantly renewed

--⇩pH of the skin ( 3 – 5 )

prevent microbial

most microbes.

from below so it can colonization.

2. Its waterproofing

keratin that makes it

dry and impermeable to pathogens.

impossible for growth of

2. Skin glands also secrete lysozyme, lysozyme an enzyme can

break down the outer wall of certain bacteria.

3. Hair follicles---oily follicles-

Mucous membranes - 2

‫هام جدا‬

☺ cover respiratory, gastrointestinal, and urogenital tracts. ☺ Mucous membrane consists of: 1. underlying C.T 2. outer epithelial layer

3. mucous secretions 4. Cilia

mucous secretions 1. Mucous viscosity entraps M.Os 2. Dilution to irritants 3. The polysaccharides prevent M.Os from binding to their receptors in either epithelial or C.T cells 4. Contain IgA – block receptors on m.m – Neutralization of microbial toxin – Aggregate and agglutinate of m.o

Cilia covering mucous membranes of respiratory or alimentary tracts propel or sweep out mucous- entrapped pathogens from these tracts.

5. Defensene : – destruction of cell wall of gram +ve bacteria

Eye- 3 Tears contain lysozymes and phospholipase make cleavage to Gm-ve bacteria and destabilize bacterial membranes Ear - 4 Waxy materials ( low Ph and + chemical nature ) prevent M.Os entrance and growth Nose - 5 It’s mucous secreations make sticking to M.Oshair entrapped M.Os It’s

How How m.o m.o overcome overcome skin skin and and m.m m.m barriers barriers 1-Skin Skin 11. Through skin injury 2. Penetration of contaminated sharp object so, M.o reach to B.Vs then reach to suitable sites for growth and multiplication 3. Via insect bites Ex, • Malaria • Plague ( Yersenia Pestis via fleas bites) 3. Few bacteria can metabolize sebum and live as commensals in the skin Ex, • Teenager acne : caused by Staph. Epidermidis which invade hair follicle prevent L.A and F.A slight irritation to hair follicle inflammatory cells accumulate in this sites Mucousmembranes membranes 22- -Mucous 1) Influenza virus Has surface molecules neuraminidase that act as enzymes and dissolve this mucous and decrease viscosity so, free the virus from entrapping and can bind to its receptor and replicate.

2) Neisseria gonorrhea Which cause Proxilla disease ‫ السيلن‬, this bacteria have glycoproteins and glycolipids projections (fimbriae or pili) that enable them from binding firmly to the urogenital tract epithelia so they can’t swept out easily

3) Treponema palladium Corkscrew movement so can penetrate m.m cause sphilis ‫الزهري‬

2.Biological 2.Biological barriers barriers

‫هام جدا‬

The normal flora of the skin and in the gastrointestinal tract can prevent the colonization of pathogenic bacteria by: )Biological value of micro flora( 1. Produce many antibacterial compounds , antimicrobial agents that inhibit invasion of pathogenic m.os 2. Compete with pathogenic m.os on nutrients 3. Occupy and block receptors which requirement for attachment of pathogenic bacteria with epithelia 4. Change PH producing unsuitable environment for other pathogenic m.os as : • Vibrio in vagina • Lactobacillus in milk convert cellulose to lactic acid

5. produce some useful materials as vitamin K vitamin B (antioxidant) prevent aging of cells 6. keep stability of temperature of body Micro Micro flora flora may may convert convert to to pathogenic pathogenic m.os m.os under under specific specific ::conditions conditions 1. Successive using of anti-bacterial compound 2. Misplacing to m.os 3. Suppressing of immune system 4. Stress 5. Malnutrition 6. Sudden change to diet 7. Drugs as cortisone , exposing to 2nd bacterial infection 8. Traveling for long distance

To compensate normal flora: • Medical preparation as Lacteal • Yoghurt in human , dogs

3. 3. Physiological Physiological barriers barriers Physiological barriers include temperature, pH, oxygen tension, and many soluble factors. ,Ex

PH of skin and stomach ---The low pH of sweat and gastric secretions prevents growth of bacteria

Some bacteria can overcome acidic PH :as Produce urease enzyme so, 1 - Helicobacter can overcome acidic PH and pylori cause peptic ulcer

2 - Staph. epidermidis

In skin over come acidic PH and cause acne

4. 4. Physical Physical barriers barriers (Mechanical) (Mechanical) 1- Coughing reflex Expel m.o which attached to ciliated mucous membrane with mucus or sputum 2-Diarrhea In food poisoning cases 3- Repeated urination In urinary tract infection , flushing to m.o , pus cells and excess salts which may lead to stone formation

4. 4. Chemical Chemical mediators mediators Non specific humeral ( )mediators

1 - Complement system Once activated complement can lead to

✏ ✏ ✏

increased vascular permeability Recruitment

‫تجنيد او تطويع‬of

phagocytic cells

lysis and opsonization of bacteria .

2 - Lysozyme and phospholipase found in tears, saliva and nasal secretions ( all fluid except urine , CSF ) can breakdown the cell wall of bacteria and destabilize bacterial membranes . 3 - Interferon ( α β ) are proteins that can limit virus replication in cells so, prevent m.os to invade other cells , then m.os float in blood and phagocytosed by phagocytic cells 4 - Properdine Activate complement 5 - Collectin Glycoprotein that block the receptors of most of Gm +ve bacteria

5. 5. Inflammatory Inflammatory barriers barriers Tissue damage caused by wounds or by microbial invasion induces a complex sequence of events as: 1. Vasodilatation 2. Leukocytic infiltration 3. Redness 4. Hotness 5. Bain

These events will increase:

The blood supply Acute phase proteins Soluble antimicrobial fluids Phagocytic cells Nutrients to the inflamed area Temperature So, microbial spreading can be stopped.

6. 6. Phagocytic Phagocytic barriers barriers (phagocytosis)

☹ ☹

One of the most effective innate barriers

Phagocytosis is ability of phagocytic cells to :

‫هام جدا‬

consider a transitional stage between nonspecific and acquired specific immunity 1. Ingest particulate materials , pathogen through receptors in their surfaces 2. Digest these substances within lysosome 3. Processing and presentation Ag determinants (epitopes or finger prints) to the T helper to initiate the specific immune response 4. Repair damage by destroying and absorbing of dead materials

Phagocytic Phagocyticcells cells Microphages

Granulated multi nucleated

1. Neutrophil 2. Eosinophil 3. Basophil The largest nucleated cell of blood which developed into macrophages when migrate to tissues


Mono nucleated

After migration of monocytes from blood to tissue become macrophages


Mono nucleated

B- lymphocytes Denderitic cells

â˜ť Body produce 3.7 x 10


monoblast /day in the B.M which

still in blood for: 10 -12 hours

3 - 5 days

In presence of IFN- and IL - 2 in high concentration

In presence of IFN- and IL- 4 in high concentration

turn to monocytes

turn in to denderitic cells

Then migrate to tissue

Classification of Phagocytic cells Poly-morphonuclear cells 1-According to cell morphology

Mono-morphonuclear cells

granulated cells 2-According to cytoplasmic granulation

3-According to life span

non granulated

short-life span long-life span

Neutrophils Basophils Eosinophils Monocytes macrophages B cells Denderitic cells Neutrophils Basophils Eosinophils Monocytes macrophages B cells Denderitic cells Neutrophils Macrophages Denderitic cells

4-According to inflammati on type

5-According to their distributio n 6-According to their function

Acute inflammation macrophages Chronic inflammation macrophages

Free or wondering cells --circulate in the blood Resident(Fixed) cells they harbor in the organs Professional Non professional

Organs or tissues

Neutrophils monocytes tissue macrophages neutrophil monoicytes

Examples in table ➊ The difference between them in table ➋

➊ ➊Table Table Name of the phagocytic cells

Connective tissues




Serous cavities

Pleural and peritoneal macrophages


Langerhans cells


Von Kupffer cells


Alveolar macrophages


Mesengeal macrophages


Microglial macrophages

Lymph nodes

Interdigitating macrophages

Synovial fluids

Synovial A cells


Langerhans and histiocytes(Malbigian cells)

➋ ➋ Table Table ➋ 1- Localization

2- Receptors 3- Opsonization

‫هام جدا‬


non professional

Lymphatic tissues

Connective tissues and organs

Complement: C3b , C3d Immunoglobulins: IgG , IgE

Non-specific receptors



4- MHC class

MHC-I and II


5- Adherence


Not adherent

6- Lysosomes



++++ Contain alkaline phosphatase


8- phagocytosis



9- Ag presentation



10- Lymphocyte interaction



7- Lysozyme secretion

Events of of Events phagocytosis phagocytosis 1- Chemotaxis macrophages attract to the site of infection 2- Adherence or attachment microorganisms are attached to specific and nonspecific receptors on macrophages surface. This binding depends on size and nature of the particles. N.B

Phagocytic receptors

11- Fc Fc receptors receptors Bacteria + IgG (have the Fc regionon their surface )can bind to the receptor on phagocytes . 22- Complement Complement receptors receptors Phagocytic cells have a receptor for the 3rd component of complement, C3b . 33- Other Other Scavenger receptors receptors Toll-like receptors receptors 3- Ingestion (phagosome formation)

â˜ťthe plasma membrane of phagocyte gradually surround m.o

â˜ť The cytoskeleton in the phagocyte is reorganized,

helping to facilitate the extension of the membrane around the particles

â˜ť each receptor sequently interacting with a binding site much like the operation of zipper

4- Digestion and killing (phagolysosomes) Once phagosomes formed, they directed to the perinuclear area where they fuse to lysosome to form secondary phagosomes, phagolysosomes. Within the phagolysomes, the microbes get killed and then digested at acidic pH and by more than 40 enzymes within the lysosomes. phagosomes phagosomes


lysosome lysosome

the themicrobes microbesget getkilled killedand andthen thendigested digested

phagolysosomes phagolysosomes  acidic pH  Lysosomal enzymes

5- Mechanism of killing Respiratory burst associated with phagocytosis leads to increase in the oxygen consumption and activation of oxidases. These oxidases reduce molecular oxygen to superoxides, hydrogen peroxide that form hydroxyl radical and singlet oxygen that have a very powerful antimicrobial effect and inhibit the microbial growth.


oxidase (reduction)

Superoxides ) ( O -2 +

hydroxyl radical

hydrogen peroxide

singlet oxygen

H2O2 that have a very powerful antimicrobial effect and inhibit the microbial growth.

Phagoso lysosome



Events associated with phagocytosis and microbial killing 1- Increase in phagocytic cell size A- Morphological and phenotypic changes

2- Increase in the number of cell organelles including lysosomes and mitochomderia 3- Increase in Fc and C3b receptors. receptors 4- Zippering of cell receptors and increase the membrane fluidity 1- Increase cell phagocytic capacity

B- Functional changes Ů?C- Biochemical changes

2- Increase in the lysosomes hydrolytic enzymes 3- Increase responsiveness to lymphocyte activation 1- Increase in the glucose and ATP production 2- Oxidative burst formation 3- Acid pH

Complementsystem system Complement • Definition

Is a group of complex plasma protein play important role in non specific humoral immunity to overcome microbial infection ( bacteria , virus , parasites , fungus )

• Characters

1. Formed from glycoproteins composed mainly by liver hepatocytes also by blood monocytes, tissue macrophages, and epithelial cells of the gastrointestinal and genitourinary tracts. 2. These components constitute 5% of the serum globulin and 20 % of total plasma protein 3. Its production during foetal life varies with species 4. It doesn’t transfer through placenta 5. Present in serum , body fluids except CSF and urine 6. Present in a very high concentration in Guinea pig’s 7. serum and plasma (fresh serum of Guinea pig is always the source of it in the laboratory work 8. Thermolabile and easily destroyed by heating at 56 o C for 30 minutes or for 1-2 hours at room temperature 9. It preserved by freezing at -20 oc or lypholyzation (freeze drying) but its better to be used fresh and can stored at 4 oc 10. Circulate in the serum in inactive forms as proenzymes, or zymogens, which are inactive until proteolytic cleavage, which removes an inhibitory fragment and exposes the active site.

11. Complement is a fast-acting, cascading system, with most effects occurring within a few minutes 12. Complement composed of at least 30 fraction either named fractions or inhibitors of complement 13. Complement components are designated by numerals‫اعداد‬ (C1–C9) , by letter symbols (e.g., factor D), or by trivial‫عادي‬ names (e.g., homologous restriction factor) . 14. Most of the complement fractions have cell receptors on immune cells and other somatic cells 15. Complement formation is independent on Ag stimulation i.e. doesn’t increased in amount by immunization 16. If concentration of complements is increased than normal needs it lead to adverse condition , out control , act against host it self 17. Complement have 2 fragment • Small “ a ” • Large “ b” Large fragment ( b ) is the active portion , except C2 the large and active fragment is (a) C3 or C4 a



C2 a


Some microbes can overcome normal pathway of complement By production of pseudoimmune mediators : stimulation of complement like substances to keep its level normal but not active immunologically ⇨ not detected by lymphocytes The most immunoglobulin activator for complement is IgM If add distilled water to complement ➙ because it is lacked in ions Ca ++ , Mg ++

-ve reaction


C 5b - 9

Cell lysis : irreversible damage to cell membrane called membrane attack complex ( MAC )

C 3a , 5a

1. 2. 3. 4. 5. 6.

C 3b , 5b

Have opsonization effect i.e. promote phagocytosis and Ag-Ab adherence by serving as an attachment sites for WBCs , platelets that have receptors for it

C 3a , 5b

Chemotactants :attract leukocytes that in turn release lysosomal enzymes and may cause tissue damages

Anaphylaxis : hypersensitivity (allergic reaction) Releasing of histamine after degranulation of mast cell Degranulation of eosinophils Increase of vascular permeability and vasodilatation Aggregation of platelets Promoting inflammatory responsibly acting on mast cells , polymorphnuclear cells , smooth muscles

Environment needed for action of complement system

1. 2. 3. 4. 5. 6.

Ca ions in the first step of activation Mg ions in the second step of activation Ionic strength of the media PH = 7.2 Temperature between 30 - 37 oc Activators as :  Ag-Ab complexes  Many strain of gram negative bacteria and its lypopolysaccharides in cell wall  Many strain of gram positive bacteria and teichoic acid in its cell wall  Fungal and yeast cell wall (zymosan)  Viruses and virus infected cells  Parasites as trypanosomes  Aggregation of IgM , IgG, and IgA  Cobra venom factor  Insect bite N.B, people whose live in desert exposed to snake or scorpion biting have high titre of complement in their serum blood than other people

Mechanism of complement activation A – Classical pathway Ca ++

Ag –– Ab Ab ➊ Ag


Ag Ag –– Ab Ab CC 1q1qrrss


Mg ++

Ag Ag –– Ab Ab CC 11q r s



Ag Ag –– Ab Ab CC 11q r s CC 44 qrs



Ag Ag –– Ab Ab CC 11q r s CC44b

Ag –– Ab Ab CC 11q r s CC44 ➌ Ag qrs



CC44 a


Make other biological function

➍ Ag Ag –– Ab Ab CC 11q r s CC 44b qrs




CC 44 CC22 b a

CC 22



CC 22 b


C 3 convertase C 3 convertase

➎ CC 33


CC33 b


CC33 a


Found in high concentration so precipitate on surface of m.o

Call ‫ييستدعي‬

➏ CC 33bb


& CC 66



CC 55 667788 b b

CC 55 667788 b b


CC 99


activate CC 88

Precipitate on m.o

CC 55 66778899 b b

10 : 20 of it is polymerase

Membrane attack complex (MAC)

Cell Cellwall walllysis lysis • • Release cytoblasmic components Release cytoblasmic components • • Disturbance of salt concentration Disturbance of salt concentration • • Penetrating and entrance of proteolytic enzymes Penetrating and entrance of proteolytic enzymes

B – Alternative pathway Initiators Initiators bacterial endotoxins snake venom insect bitting Prescence of aggregates of IgG , IgA Bacterial lipopolysaccharides

Activate or spontaneously activated

CC 33

CC 33 b b Properdin

CC 33 b b

CC 33 b b


CC 33 b b


CC 33 a a

In high concentration

CC 33 b BB bb b

Factor Factor BB


CC 33 b BB bb b

Factor D

For For amplification amplification ‫ييزوده‬ ‫ييزوده‬

‫ بكميات‬C 3 b ‫يتبقي‬ ‫كبيرة‬

CC 33 b b

Then Then the the same same biological biological mechanism mechanism as as in in classical classical passway passway

C – Lectin pathway

CC 44



Lectin Lectin binding binding protein protein


CC 33

CC 22

CC 44 CC 22 C 3 convertase

In high concentration

‫هام جدا‬

A- Classical pathway

B- Alternative pathway

C- Lectin pathway

Specific immunity

Non - specific immunity

Main player C3

Main player C3

Co-players : • C1, C2 , and C4, • Ca , Mg ions

Co-players • Properdin • Factor B • Factor D • Factor H

C3 convertase C4bC2a

C3 convertase C 3b B b

C3 convertase C 4C 2

Activators 1. Immune reaction (Ag – Ab reaction) 2. IgM and certain subclasses of IgG (human IgG1, IgG2, and IgG3)

Activators 1.Bacterial endotoxins 2.Bacterial lipopolysaccharides 3.Snake venom 4.Insect bitting 5.Prescence of aggregates of IgG , IgA

Activator Prescence of “lectin binding protein “ on bacterial , fungal cell wall as in : • Myobacteria • Actinomyces • Some protozoa as trypanosomes


Main player C 3 :

Co-players : • C 2 and C 4




C 1 qrs


ٍSpecific immune response

Immunogenicity (antigenicity )

Ag • Certain substances induce detectable immune response when introduced into host • Any substance which react with Ab called Ag .. whether it is Abproducer or not • it called immunogenes (specifically) or antigen (generally) This Ag may be (2) Polysaccharide or synthetic polypeptides

(1) protein

The most potent

Immunogenic under appropriate condition

(4) Pure nucleic acid

(3) lipid

Not antigenic but become Ag when complexed with protein or polysaccharides

Not shown to be Ag

Ag also may be (1) particulate

(2) soluble

Bacteria , virus , …… large protein Polysaccharide molecules Egg white Snake venom

Soluble tissue constituent of animal and plant

•The immune response may be (1) Humoral

(2) cellular

(3) both

Ab production

Mediated by T-cell

Most common

Ag determinant sites (ADS ) ( finger print ) (epitopes ) • Although Ag is macro molecule with high molecular weight , but the immunologically function part of Ag called epitopes • very small sized portion (200 -700 ) Ao (square angestrom) • They may be repeated part of molecules – e.g ⇨ egg albumin

• Their numbers , structure , location are of value in determining the type , intensity of immune response • Each determinant site = 10 – 15 A.A • Every 5000 D on the peptide chain have one determinant site Ag


Have multiple determinant sites ( multi specific multi valent )

Have 2 similar reaction sites on each end (mono specific bivalent paratope) paratope : the part of an antibody that recognizes the epitope






Monogenous binding of bivalent Ab to 2 determinant sites on an Ag particles

Hapten • Small material of low molecular weight which can’t induce immune response by itself .. but conjugate with carrier to induce immune response E.x ⇨ penicillin : no immune response – But , penicillin + Albumin (cell protein ) ➙ ⇧molecular weight ➙ immune response

Factors determining Antigenicity ( requirements to be Antigenic ) 1- Foreignness

Ag must be foreign (non-self ) to the body where immune system don’t respond to its self Ag E.x ⇨ Albumin isolated from rabbit serum injected into same or other rabbit won't generate formation of Ab

2- Molecular weight

The higher molecular weight the more antigenic Macromolecular protein (> 10 000 ) Dalton is potent Ag

3- Molecular surface

• The large molecular surface the more antigenic • Charcoal or aluminum hydroxide non Ag due to low molecular surface .. Become Ag when absorbed into inert particles due to display of significant groups on surface

4- Rigidity

• Hydrocarbon posses a large molecular weight and large surface but it can’t act as Ag due to loss of rigidity

5-Chemical complexity

• The more complexity the more antigenic as synthetic poly peptides • Virus ⇨ more complex ⇨ high immunogenic homo polymers Composed of repeated 1 or 2 A.A weak Ag

Co ploymers Composed of different A.A Strong Ag

• So.. Lipid , carbohydrate , nucleic acid ➙ are mono amino acid polymers ➙ poor antigenic • While addition of aromatic A.A ( tryptophan , tyrosine ) ➙ increase immunogenicity

Immunoglobulin (Ig) ( Specific humoral immunity( All immunoglobulin are Ab but not all Ab is immunoglobulin Characters of humoral immunity • React only with Ag that induce its production • But some Ab has cross reaction : can interact with more than 1 Ag as :

1- Specific in action

– HCV X Schistosoma⇨ false result (PCR recommended ) – HCV X Protein 3 of Influenza V. (PCR recommended ) – Flariasis X Entamoeba histolytica (isolation of m.o recommended )

2- Clonal expansio n

Reexposure by the same m.o : Immune cells respond rapidly ⇨proliferate⇨differentiate and divided ⇨form a clone of cells (group of daughter cells from one mother only )

3Formatio n of memory response

By second exposure to infection ⇨ Ig has ability to rapid proliferation ⇨ magnitude the immune response

Specific characters of Ig 1. Produced only by lymphocytes in spleen , liver , lymphnodes , lymphoid associated tissues 2. The main Ig secreted cells are • plasma cells (Produce 93 % ) of Ig • B – cells ( produce the rest 7 % of Ig ) 3. Has ability to fold and re-fold Ag ‫ال تتحور علي شكل‬ 4. Present in all body fluid except CSF & urine 5. Its concentration in body decrease respectively as follow: • Blood (serum +plasma) • Milk , seminal fluid • Vaginal mucous (in certain condition ) • Urine & extracellular fluid in pathogenic condition as cancer of plasma cells in B.M (myloma ) 6. Ig constitute 20 % of serum protein 7. Is part of ૪- globulin fraction of serum protein


Albumin produced mainly by liver


૪- globulin secreted only from Lymphocyte


Concentration of ૪- globulin different due to exposure to infection , immunization

8. Heat resistant except IgE : heated in W.b at 65 oc ➙ no coagulation

Structure of immunoglobulins 1) Normal shape of Ig in inactive stage ( no m.o / no infection ) is T-shape and inactive stage Y-shape 2) Molecular weight 150 KD 3) Consist of 4 poly peptide chains according to molecular weight

Heavy chain

Light chain

4400 A.A



55 – 60 KD

25 KD

5 types according to Ag determinant

2 types :













λ NH2 nitrogen (amino )terminal

FAB fragment of( )Ag binding

FC fragment of( )crystallization

)CooH (carboxyl terminal

4) Two chain bond with each other by disulphide ponds S=S (covalent inter chain bond ) which held 2 heavy chain with each others and 2 light chain with heavy chains it rich in sulpher A.A (cystine , cystein , valin , methylin ,…. ) which stretch it self (fold & re-fold )

5) Each chain consists of :

variable region

constant region

Which contain high varieties of A.A

Few degree of variability


Hinge region‫منطقة المفصلة‬ • Area between constant and variable region • Highly flexible • Sensitive to enzymatic and chemical action


1- Fragment of Ag binding

1- Fragment of crystallization

2-Present to ward amino terminal

2- Present to ward carboxyl terminal

3- Contain variable region and part of constant region

3- Contain the rest part of constant region

4- For specific binding to Ag

4- Biological function of FC portion of Ig ‫هام‬

Ag FAb Fc portion


epitoprs MHC

IgG 1. The only pass through placenta Ab 2. Complement fixation 3. Bind to macrophage 4. Opsonization IgE 1. Bind to mast cells initiate hyper sensitivity reaction (vasodilatation , produce active serotonin , histamine , broncho - constrictor )

Classification of Ig I – According to chemical structures of heavy chain ( amino acid sequence ) G





‫هام جدا‬

[1] • • • • • • • •


Represent about 75 % of total Ig Molecular wt. = 150-180 KD Formed from 6 constant region , 4 variable region Main Ig in secondary infection appear after IgM Persist for larger time , its life span 23 days The only Ig which pass placenta (source of defense in newly born ) Monovalent So not effective in acute infection Function : 1. Act against viruses , bacteria , toxin 2. Lysis to m.o 3. Neutralize Ag 4. Opsonization : Mycobacterium , Leptospira , Niseria ⇨ agglutination ⇨hider its movement so be easy to catch by phagocyte 5. FC portion bind with complement and to receptors of phagocytic cells

[2] • • • • • • • • • •


Represent about 5-10 % of total Ig Highest molecular wt. = 400 KD Life span =5 day Largest , heaviest Ig Star shape , pentomere , composed of 5 basic units which joint to gather by J-chain so , can attach to 10 m.o Appear in primary infection but not persist for long period Have a very strong receptors for complement fixation due to high complicacy of it Most agglutinable Ag Neutralization capacity is low in comparing with IgG Present in high concentration in blood but in very low concentration in other body fluid J- chain

[3] • • • • • • • • • • •


Represent about 20 % of total Ig Molecular wt. = 150 -300 KD Monomer form Predominant Ig in mucosal surface , external secretion (saliva , tears , sweat , urine ) Most advantage : trapping Ag with mucous layer ⇨ preventing its absorption ⇨ Stimulate of more army of immune syste High binding capacity to pathogens Only Ig secreted in milk so give protection of newly born Its production is mainly due to local stimulation (not affect by increase serum IgA ) No complement fixation but activate alternative pathway Vaccine must stimulate IgA as natural immunity Less Biologically active than other Ig



• Binding to receptors on B-lymphocytes in inactive form • Its specific role in immunity still unknown



• Highly predominant in hypersensitivity & parasitic manifestation binding to mast cells • Naturally = 0.003 mg/ml blood , in infection reach 1 mg

II – According to Ig function properties As toxoid of Tetanus 1- Toxin neutralizing Ab

2- complement fixation to receptors on phagocytes




75 %

20 %

0.3 %

IgE 0.003 %

Activation of C5 insertion of cell wall of bacterial cel l⇨ C8 ⇨ C9 ⇨ polymerization ⇨ cell lysis IgM



> IgA

3- lysis to bacterial cells

Mainly IgG

4- Agglutination Ab (Agglutinin )

Agglutinate m.o to prevent their movement to be easily phagocytosed IgM > IgA > IgG

Classification of Ig I – According to chemical structures (amino acid sequence ) of heavy chain G

Heavy ch. Produced in M.wt Conc. in serum














150-180 KD

400 KD Largest one

150-300 KD

75 %

5 -10 %

20 %

0.003 mg/ml bl.

40 mg/ kbwt /day

Main Ig in 2ndry infection

Main Ig in primary infection

Main Ig in mucosal surface

Bind to Blymphocyt e

In hypersensit ivity & parasitic manifestati on


Pentamer Star shape

Monomer or dimer




Very power full +++


Unknown function


Memory response

Main Ig





Placental barriers

Only pass





+ Low







In Secretory IgA



Role in infection Basic unit Fixation of complemen t

Agglutinatin g capacity J-chain

‫ييتحد مع ميكروب‬ ‫واحد‬

Primary immune response Characterized by : 1.

Secretion of IgM


Take long time


Decline rapidly


Magnitution of Ig is limited


IL -2 5 6 activate division of B-lymphocyte ⇨ proliferation , differentiate give plasma cells , memory cells

Ig concentration


period M.O Bacteria , virus , parasite

• Macrophage • DC • Monocyte

T-cells ,proliferation differentiation

• Neutrophil

days 5 - 3

Formation of finger print of causative agents then presentation of Ag to T-cells

days 7-15

Then decline at 21 days

Secondary exposure to same infective agent ( secondary immune response ) ( memory response )

Characterized by : • • •

• • • •

Very high production of Ab than in primary immune response Rapid response due to memory cells Secretion of IgG (generalized infection )

Persist for long time , at least 6 months (long lasting immunity ) Highly effective Neutralize microbial toxins or occupy its receptors Plasma cells , memory cells in blood and l.n


period m6

So , In vaccination must give booster dose after 21 day because immunity decline after 21 day from booster dose , so must stimulate immune cells , memory

Mucosal immunity ( External surface immunity ) ( Secretory immunity ) (Secretory IgA ) Distribution of Ig in external , internal cavities ( surfaces ) : Mucosal immunity protect mucosal surfaces of RT , GIT , UGT , mammary gland ) which are in direct with the external environment ( a major site of Ag exposure ) IgA was the predominant Ig of external secretion IgA : IgG = 5 :1 in mucosal surface External surface 1. Mucous membrane

Internal fluid

Blood ( Serum , plasma(

2. Nasal fluid 3. Milk IgA

( % 75 )

IgG 10-15) (%

IgM IgE ( % 1.5) IgD ( % 1) ( % 1)

Ig concentration

Ig concentration

( % 80 )


( % 15 )

IgM IgE ( % 10) IgD ( % 3) 0.003) (%

Ab at mucosal surface produced by plasma cell (present in lamina propria of secretory sites such as : gut , respiratory , nasal mucosa , salivary gland )

Mechanism of IgA secretion from mucosal surfaces M-cells :

Mechanism of action in mucosa

– Phagocytic cells – modified epithelial cells – Micro folded epithelial cells – Non- ciliated – Play a very important role in initial immune response on mucosal surface

Ig Ig A A

Mucosal Mucosal immunity immunity Basement membrane

Sub mucosa


lymph vessels

‫الجزء الكبر‬ ‫منه يينتقل الي‬ intracellular space

➏ ➊

Blood vessels

Ab Ab

Ig A

‫ييخرح لل‬ mucosal lumina 3 ‫وييعمل‬ ‫وظائف‬

‫هام جدا‬


plasma cells

Memory cells

➋ M-cell



Phagosome proliferation

Epithelial cells B Macrophage

➍ ➌

Th IL-1


1. Trapping of m.o by M-cells ➙ forming phagosome 2. Processing of Ag by M-cells or Macrophage (present in sub mucosal in abundant amount )

3. Presenting of Ag determinants ➙ releasing IL1 ➙ activate Thelper which attached to macrophages ➙ activate IL2 4. IL-2 activation of B-lymphocyte ➙ proliferate then differentiate to give plasma , memory cells 5. Plasma cells produce Ab 6. Ig transport from mucosa to sub-mucosa reach blood and lymph ➙ systemic circulation 7. But , the large amount of IgA absorbed in mucosal surface as follow : 1. 2.

IgA synthesize a secretory component which attach to receptors on basement membrane So IgA accumulate in intracellular space then passed to mucosal surface and the lumina

• Importance of secretory components : 1. 2.

Facilitate transcellular transportation of IgA from submucosa to mucosal lumina Protect IgA from digested by proteolytic enzymes

• Role of IgA 1. 2. 3.

Occupy binding sites of m.o and prevent their attachment and colonization on gut surface Neutralize microbial toxins Aggregate and agglutinate

Immunity Immunity

Specific Specific immune immune response response

Non Non specific specific immune immune response response

))Acquired Acquired ((

))Innate Innate((

))Adaptive Adaptive((

))Natural Natural((

Cellular Cellular immunity immunity

Humoral Humoral immunity immunity

Cell Cell (( mediated mediated ))immunity immunity

Ab Ab(( mediated mediated ))immunity immunity

Physical Physical

Chemical Chemical Biological Biological

Cellular Cellular Inflammatory Inflammatory

Physiological Physiological

Humoral Humoral ))(complement (complement

Cell involved in immune response 1. Macrophage 2. Killer and Natural killer 3. Lymphocytes • T-lymphocyte • B-lymphocyte

killer cells , natural killer cell • One of the immune cells • Have large number of receptors (Fc receptors ) which attach with Fc portion of Ab • Have a role in Ab dependent cell mediated cytotoxicity [ ADCC ]

ADCC ADCC Pathogen infected cell

Ab Fc receptors as CD 16

Fc portion of Ab

Killer cell

Condensation of molecule beside membrane

Perforin form pores in target cell membrane

Cell apoptosis

Killer cell

Natural Natural killer killer [[[[ NK NK

‫هام جدا‬

1. antibody, such as IgG, bound to the surface of a pathogeninfected cell. 2. An NK cell's Fc receptor recognizes the Fc portion of an Ab 3. activation of NK cells 4. The most common Fc receptor on the surface of an NK Cell is called CD16 5. Once the Fc receptor binds to the Fc region of IgG, the Natural Killer cell releases cytokines such as IFN-γ, and cytotoxic granules containing perforin and granulysin – Perforin :form pores in the terget cells membrane – Granulysin :allow granzymes to enter the target cell ➙ a poptosis

Remember : ● ● ● ●

Cell mediated immunity more efficient than humoral immunity Ab act on cell surface of macro molecule Ab can’t kill m.o , stop it only Ab block foreign bodies receptors

The major histocompatibility complex (MHC) • Is a gene present inside cells and plays an important role in the immune system • Expressed the protein enter the cell on the surface of cells to T cell • This protein may be either Self

… peptide fragments from the cell itself

or –

Non self …. as bacteria , virus

Epitopes • Unique structure carried on Ag surface attach to Ab • It is not mutable ( as PAMP ) but short chain 10 a.a • Always associated with MHC to facilitate Ab recognition formed what is called “ Ag peptide MHC complex ” Ag peptide -MHC complex

• Complex between Ag and immune response • It is a transient stage between non specific ( preparatory stage ) and specific (cell mediated immunity ) • If formed from 18 a.a … attached to MHC II call B-lymphocyte If Ag formed from 10 a.a … attach to MHC I T-cytotoxic


‫هام جدا‬

Pathogen-associated molecular patterns • The molecules associated with groups of pathogens • Don’t undergo mutation .

Gram–ve bacteria

Gram+ve bacteria

Lipopolysaccharide )LPS) (on the bacterial cell membrane )




Nucleic acid


• These PAMP are recognized by pathogen recognition receptors (PRR ) which present only in immune cells


‫هام جدا‬

Pathogen Recognition Receptors

• Are proteins expressed by cells of the innate immune system to identify PAMPs • They include – TLR's ) Toll-Like Receptors) – CD


( Cluster of differentiation 14 )

– CR


( Complement receptors 3 )

– FCR – CD11 b – KIR – KAR

• PPR may be soluble as lipid binding protein (LBP) or membranous as (CD14 ) • Lipid A of LPS ( lipo polysaccharide ) of gram –ve bacteria bind with LBP (soluble PPR circulate normally in blood ) then attach to CD14 at the membrane of phagocytic cells give intracellular signal to produce cytokines which has 3 effect : 1. Autocrine : acts on the same type of cell that secretes it. 2. Paracrine : acts on neighboring cells 3. Endocrine : act on other site away from secreted site (as hormones) Lipid A Intracellular signal




effect 3 …

FCR Phagocytic cell

… CD 11 b



Macrophages [MΦ ] Trapping to Ag Presentation to Ag Create suitable environment to keep integrity of all immune cells

Antigen presenting cell ( APC ) 1. Macrophages 2. B- Cell 3. D-cell

T-cells • • • •

Small white blood cells which participate in immune defenses Comprise about 60 % of circulating lymphocyte They are processed in thymus , secrete lymphokines Indication (activators) of T-cell : 1. 2. 3. 4.

Intracellular m.o as virus , malaria , leishmania , parasites Carcinogens Delayed hypersensitivity Tissue grafting , cell implantation

• Types of T-cells 1. T- helper • Master of immune system • Have receptors CD2 , CD3 , CD4 • Called helper because they assist other cells of immune system as macrophages , B-cell , TC • Types : 1. T h 0 ( Naive or vergin T-cell ) ‫ من قبل‬Ag‫لم يسبق لها التعرف علي‬

2. T h 1 3. T h 2


1- Main APC

2- Cytokines produced



B - cell

IL 2 IL 3

IL 4 IL 3 IL 6 IL 10 ( in certain limit ) TGF


3- Recognition of Ag associated Ag with MHC I

Ag associated with MHC II

4- Immune response

Humoral immune response

Cell mediated immune response

N.B CD 28 present ABC attach with CD 3 on T-cells and B 7 attach with Cd 80 on T-cells

T- cytotoxic •

Receptors • CD 2 • CD 3 • CD 8 • CD 25 Secretes • Perforin • Granzyme : • IFN

protein in nature help in apoptosis

3. T- regulatory ( suppressors ) •

Receptors • CD 25 • CD 56

specific specific cell cell mediated mediated immunity immunity 1- Recognition of Ag


• N.B , T-cell receptors (TCR ) have different shapes to become complementary to all Ag shapes • MHC I present in ER while MHC II present in cytoplasm • In case of viral infection , intracellular parasites Ag integrated by protosome then translocated to endoplasmic reticulum by carrier protein or chaperon … then viral peptide bind to MHC I in ER then traffic to the surface – Chaperon is protein carriers present on the cell act on : • Modification of protein after translation • Degradation of foreign protein • Transportation of protein from cytoplasm to cell membrane through E.R • In case of bacteria or extracellular parasites the epitopes bind to MHC II in cytoplasm and transmit directly to surface

2- Activation

1. Contact signal • •

binding of Ag peptide ( presented by APC ) with T-cell But it is not enough signal require another signal

2. Secretory signal •

Achieved by interaction 0f CD 28 (on ABC ) with CD 3 (on T-cells ) and B 7 (on ABC ) attach with Cd 80 on T-cells

– Macrophage ( APC ) represent Ag on its surface with MHC molecules and produce IL-1 which stimulate T hcell to attach with Ag by its receptors then produce IL2 , IFN ૪ which activate T-cytotoxic

3- Proliferation – Then stimulation of T-cytotoxic to proliferate to give large number of cells – Then production of IL-10 which stop proliferation 4- Differentiation A. Memory cells ( small cells ) : ➙ circulation l.n , secondary lymphoid organs as spleen B. Effector cell (large cell ) ➙ attack 5- Effector phase 1. Effector cell attach to infected cells 2. Concentration of granzyme molecules of effector cells beside the wall toward the infected cells 3. Produce perforin which make pores in the wall of infected cell lead to tranportation of granzyme molecules from teffector cells to infected cells 4. Granzyme molecues :melting to metochondria of m.o lead to cell apoptosis N.B , Cell mediated immunity is effective in case of viral infection and intracellular parasites

Cell Cell mediated mediated immunity immunity

Ag Ab

IFN ૪ IL-2




IL-1 Proliferation

Infected cell

effector cell

Cell apoptosis


Large cell

Small cell

”Effector cell“

”Memory cell“

Human response

Increasing of immune cells

Chronic infection as T.B Tc

Immune cells

MŐ“ M.o


Viral infection

Complement , IFN , T-cytotoxic , natural killer

[ The diagram of cell mediated immunity ]

Capsulated bacteria

K-cell , complement , Macrophage Capsulated bacteria ➊ Ag Ab


Circulate again ➍

APC ➎ Then degradation of Ag


Neutralization of toxin directly by blocking its receptors Ab binding toxin , K-cell

How How microbes microbes evade evade or or escape escape from from immune immune response response 1. Prevention of phagocytosis : some m.os have capsule protect them from phagocytosis phagocytosis

Bacillus anthracis Streptococcus pyogens 2. Competing with Fc receptors : hence prevention of opsonization

Staphylococcus aureus 3. Inhibition of binding of lysosomes with phagosomes :

Mycobacterium tuberculosis 4. Escape from phagolysosome to cytoplasm :




5. Resistance of phagolysosome acidic pH



enveloped viruses.

6. Direct penetration of phagocytic cells So phagosome not performed and thus avoid the enzymes , lysozyme action But it used phagocytic cells as a transportation mean to spread infection




6. Mutation of their epitopes Epitopes and paratopes have complementary amino acids for each others with different charges to bind with each others If the sequence of amino acids of epitopes changed the Ab can’t attach to the new epitopes





Influenza virus

a.a sequence of HCV (valine , glutamic acid , lysine , …… ) after mutation become (glutamic acid , valine , ……. ) 6. Mimicry



Steal host protein and precipitate it around themselves so phagocytic cells can’t recognize it (disguising ‫)تنكر‬




6. Create protein like substances similar to host protein :

Streptococcus pyogens Secreate streptolysin A which similar to myocardial protein so, lead to production of component similar to host components

10. Production of Ig like substances

HCV Stimulate hepatocyte to secrete Ig like substances and complement like substances leading to stop the function of immune system to produce Ab 10. Resist lysosyme action

T.B Surrounded by mycolic protein or mycolic acid (producing iron chelating materials 窶ヲ prevent iron absorption

Brucella Surround by lipid layer which protect it from lysosyme action 10. Immunoglobulin idiotype closure : Make closure to Ig idiotope by secreting anti 窶的g idiotope




Hypersensitivity Hypersensitivity

Type TypeII

Type TypeIIII





Type TypeIII III


Mechanism Mechanism of of immediate immediate hypersensitivity hypersensitivity


1-first firstexposure exposure [ [synthetization synthetizationstage stage] ] 1Allergen Insect bites , Pollen , Cosmetics , Medications Stimulate B-cells Proliferation & differentiation

Blasma cells

Ig E

Mast cells


Mast cells Eosinophils Basophils

“Caping“ Bridge formation to attach IgE with each others

2-second secondexposure exposure [ [effector effectorstage stage] ] 2Mast cells or eosinophils or basophils have already receptors to IgE


Attach to IgE which already persist on mast (cells (as example

Stimulate mast cells to produce protein kinase


Protein kinase ‫ حاجات‬3 ‫يعمل‬

1. Increasing Ca metabolism 2. Increasing energy 3. Increasing of cell skeleton

deposition of granules near cell membrane

Degranulation …..The granule release [ 1 ] Chemo attractants

Vaso active amine [ 2]

Prostaglandin [ 3]

Chemo attractants [ 1] possessing chemotaxis

• Leukotrin B • PAF “ Platelet activating factors “ • IL 1 & IL 8 1. Attraction of more immune cells to site of allergy 2. Stabilization of allergin through microthrombi ( stabilize


it to site of inflammation don’t return )

Vaso active amine [ 2]

• Histamine • Serotonin 1. Vasodilatation 2. Recruitment of more cells 3. Increased mucous secretions Prostaglandin [ 3] End result of allergy 1. Vasoconstriction of blood vessels 2. Spasm of smooth muscle ( hypotension )

Treatmentand andcontrol controlof ofallergy allergy Treatment 1. Avoid the cause 2. Epinepherin (adrenalin ) : to decrease Ca+ exit from cells 3. Anti-histaminic drugs : as Allergin 4. Corticosteroids which acting mainly on mast cells ‌ cause immunosuppresion

N.B N.B Cheotaxis: : Cheotaxis

Directedmigration migrationof ofcells cellsto tosite siteofof Directed infection infection Chemokinase: : Random Randommigration migrationofofcells cellsfrom from Chemokinase bloodvessels vessels blood

Hypersensitivityalso alsoclassified classifiedaccording accordingto tolocation location Hypersensitivity into: : into 1. Anaphylactic Anaphylactic or orsystematic systematic 1. 2. Atopic Atopicor orlocal local: : 2. Contactdermatitis dermatitis •• Contact Conjunctivitis •• Conjunctivitis ‫هام‬

Immediate Hypersensitivity

Delayed Hypersensitivity


Start after 2 min. to 2 hrs.

24 -27 hrs

Effector cells

B-lymphocyte Plasma cells Mast cell Eosinophile Basophile

T-cell (T- cytotoxic) Ag stimulate macrophage to produce cytokines which activate T-cells which divide give memory cell which migrate to l.n and site of infection

Main Ig

Mainly IgE Also IgG , IgM

Mainly IgG


Non biological origin as:

Biological origin as :

– – – –


Insect bite Pollen Cosmetics medications

Redness , skin rash

– Tuberculin – Mallein

Thickness and elevation of skin (over 4 mm ) due to oedema localized at site of Ag


• Its antigenic structure or product isolated from m.o and used to induce either cellular or humoral immune response or both of them together

Characters of successful vaccines [ 1 ] Factors related to immunology :


1. Should induce both cellular and humoral immune response 2. Memory response 3. No mutation 4. Provide immunity for long duration 5. Produce effective response against all antigenic determinants [ 2 ] Factors related to safety : 1. Not incorporated in host genome … no mutation 2. No reversion to virulent strain 3. Not lead to immune suppression 4. Don’t persist 5. Easily to be administrated 6. The vaccinated animals not become carriers ( no shedding of m.o which may affect contact animals ) [ 3 ] also should be cheap , available , suitable to country conditions

Vaccine failure


1. Reversion to virulent strain 2. Incorporated into host genome .. mutation 3. The vaccine preparation may need specific steps as cold storage which have some hazard as cutting of electric current may lead to changes in vaccine prosperities 4. The animal may be infected before vaccination 5. Incorrect dosage 6. Contamination of vaccine during the preparation , recultivation , or during application 7. Immuno comporomized animals

Types of vaccine 1- Killed or inactivated 1- Method of preparation

m.o killed or inactivated either by : 1. Chemicals as 3 % formaline 2. Physical as heating at 60 oc /1 hr. to denaturate the protein

2- Route of injection


3- Advantages

1. Very safe 2. Economic

4- Dis advantages

1. 2. 3. 4.

Short duration Require more than more dose Induce mainly humoral immunity only No memory response

2- live attenuated vaccine m.o attenuated by :

1- Method of preparation

– direct exposure to ultraviolet rays – Repeated inoculation in unsusceptible host as egg or rabbit for rabies virus – Unsusceptible temperature like brucella then subcultures for 19 times – Cultivation on inhibitory media as media contain bile salts as BCG for T.B – Withdrawal of water ..dryness and desiccation as in rabies

2- Route of injection


3- Advantages

1. Induce both cellular and humoral immune response 2. Strong memory response 3. Long lasting immunity 4. Not require more than one dose

4- Dis advantages

1. expensive 2. Make integrate with host genome , cause tumor 3. May convert to virulent strain



3- toxoid

1- Method of preparation

Maintaining antigenicity of bacteria but alternate of the toxogenic part by extraction of toxin then attenuated by chemicals as formalin 0.3% ( while bacteria it self attenuated by formalin 3% ) as clostridia tetani

2- Advantages

Most powerful

3- Dis advantages

Very expensive

4- Subunit vaccine [ protective vaccine ] Composed of only one or more of antigenic structures of the m.o that amplified by molecular engineering (by PCR )

1- Method of Then insert in other bacteria like E-coli ⇨ preparation reproduction of E-coli ⇨ breaking down of Ecoli ⇨extraction of DNA ⇨ qualification ⇨ make in doses ⇨ ready for injection 1. Safe 2. Avoid immuno suppressive epitopes 2- Advantages 3. Induce either humoral or cellular immune response according to method of preparation and the amplification of selected Ag

4- Dis advantages

1. 2. 3. 4.

Expensive Require too many doses No memory response Incomplete protein

5-Virus like particle

1- Method of preparation

Advanced technology using virus like particles , genome viral protein ⇨ amplification ⇨ insert in viral host (like vacuole virus ) ⇨ assemble virus like particles Vacuole virus is virus of insects used to not disintegrate with the virus

2- Uses

In highly mutable m.o as influenza Slow grower m.o m.o not grow on routine tissue culture M.o not has susceptible host

3- Advantages

1. Similar to natural inject 2. Very safe 3. Induce both cellular and humoral immune response 4. Induce long memory response 5. Contain immune stimulant epitopes

4- Dis advantages

1. Require more than one dose 2. Expensive


• Def

It is non immunogenic substances mixed with vaccine to increase efficiency of vaccine

• Mode of action

1. Slow release of the Ag 2. Long exposure of Ag to specific cells or immuno competent cells 3. Induce low degree of inflammation which result in attraction of immune cells (Magnification of immune response )

• Examples

1. Aluminum 2. Aluminum sulphate 3. Products of some m.o as BCG

• Types

1. Complete Freund’s adjuvant Contain mineral oil + BCG ( inactivated and dried mycobacteria ) 2. Incomplete Freund’s adjuvant Contain just mineral oil without BCG

The most important questions • Compare : 1. Innate & acquired immunity 2. Classical & alternative pathway of complement 3. Immediate & delayed hypersensitivity 4. Primary & secondary lymphoid organs • • • • • • • • • • • • • •

Phagocytosis Professional phagocytic cells Short notes on IgG Cell mediated immunity NK Mucosal immunity Mucous as physical barriers Biological barriers Characters of standard vaccine Vaccine failure Immediate hyper sensitivity Biological function of Fc Portion Short notes on PAMPs & PRR Short notes on MAC [ Membrane attack complex of complement , Nk , Cytotoxic cells ‫] ونشرح واحده منهم‬