Clinical chemistry theory analysis correlation 5th edition kaplan test bank

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Kaplan: Clinical Chemistry, 5th Edition Chapter 7: Immunological Reactions Test Bank MULTIPLE CHOICE 1. The most potent antigens are macromolecules with molecular weights greater than: a. 1000 daltons b. 10,000 daltons c. 50,000 daltons d. 100,000 daltons ANS: D

There is no absolute size requirement for determining antigenicity of a molecule, but the most potent antigens are macromolecules with a molecular weight of greater than 100,000 daltons.

DIF: 1

REF: 152

2. Haptens are: a. low-molecular-weight compounds that are unable to induce an antibody response

alone b. low-molecular-weight compounds that can induce an immune response when

coupled to higher-molecular-weight immunogenic carriers c. low-molecular-weight compounds that can react with antibodies d. all of the above ANS: D

A hapten is defined as a low-molecular-weight substance that can induce an immune response only when coupled to high-molecular-weight immunogenic molecules. The lowmolecular-weight component of the larger complex reacts with the antibody. Examples of haptens include lipids, hormones, and drugs.

DIF: 1

REF: 152

3. The portion of an antigen involved in a reaction with an antibody is known as the ____

site, and the number of these sites on an antigen is known as the antigen’s _______. a. equivalence, valency b. equivalence, complexity c. antigenic determinant, valency d. antigenic determinant, complexity ANS: C

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The portion of the antigen involved in the reaction with the antibody is known as the antigenic determinant site. An antigen may have more than one antigenic determinant site. The number of antigenic determinant sites on an antigen is known as the antigen’s valency. The valency is the number of antibody molecules that can be bound to the antigen.

DIF: 1

REF: 152

4. Which of the following antigenic determinants would be the most reactive? a. an antigenic determinant located in the core of a spatially folded molecule b. a sequential antigenic determinant c. an antigenic determinant located on the surface of a spatially folded molecule d. the exposed antigenic determinant of a denatured protein ANS: C

The reactivity of an antigenic determinant is based on many factors. Two of the factors include conformation and accessibility. A molecule’s three-dimensional shape and spatial folding relate to the molecule’s conformation, which is a significant factor in immunogenicity. In addition, accessibility of the antigenic determinant for interaction with the antibody is also an important factor. The more accessible the antigenic determinant site, the greater the antigen-antibody reactivity.

DIF: 2

REF: 153

5. Antibodies are ______ that are produced by the _______. a. lipids, adipose cells b. carbohydrates, bone marrow cells c. nucleic acids, hepatocytes d. proteins, B lymphocytes ANS: D

Antibodies are primarily protein (82% to 96%) and are chiefly produced by a subset of lymphocytes known as B lymphocytes.

DIF: 1

REF: 154

6. The portion of the immunoglobulin molecule that binds to antigens is: a. the Fab-fragment portion b. the Fc-fragment portion c. the hinge portion d. the disulfide-linkage portion ANS: A

The Fab (fragment antigen binding) fragment is the portion of the immunoglobulin molecule that binds to antigens.

DIF: 1

REF: 154

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7. Which of the following statements best describes the region of the immunoglobulin

molecule that is responsible for specific binding to the antigen? a. The constant regions of the heavy and light chains in the Fab fragment interact to form a specific antigen-combining site. b. The variable regions of the light and heavy chains in the Fab fragment interact to form a specific antigen-combining site. c. The constant regions of the heavy and light chains in the Fc fragment interact to form a specific antigen-combining site. d. The variable regions of the light and heavy chains in the Fc fragment interact to form a specific antigen-combining site.

ANS: B

It is the interactions of variable regions of light and heavy chains that form a specific antigen-combining site. The remainder of the polypeptide is composed of polypeptide segments that are similar among other immunoglobulins. These polypeptide segments are known as constant regions.

DIF: 2

REF: 155

8. Is the following statement true or false? If false, identify the part of the statement that

causes it to be false.

Kappa and lambda light chains differ in the amino-acid sequence of their constant regions. A given antibody always has two identical kappa light chains or two identical lambda light chains. An antibody molecule can never have both a kappa and a lambda chain. a. true b. false, light chains have the same amino-acid sequence in their constant regions c. false, a given antibody can have different kappa or lambda light chains in the same molecule d. false, an antibody can have both a kappa and lambda light chain in the same molecule ANS: A

All three components of the statement are correct.

DIF: 1

REF: 155

9. Which immunoglobulin can cross the placental membrane? a. IgA b. IgD c. IgM d. IgG ANS: D

IgG molecules can cross the placental membrane and are responsible for the immunological defense of the newborn.

DIF: 1

REF: 155

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10. Which immunoglobulin exists primarily as a pentamer and is the predominate

immunoglobulin in the initial immune response to an antigen? a. IgM b. IgE c. IgA d. IgD ANS: A

IgM exists primarily as a pentamer, with five immunoglobulin monomers held together by disulfide bonds. IgM is also the predominate immunoglobulin in the initial immune response to an antigen.

DIF: 1

REF: 156

11. Which immunoglobulin is the predominant immunoglobulin in body secretions such as

saliva and sweat? a. IgE b. IgA c. IgD d. IgG ANS: B

IgA is the predominant immunoglobulin in body secretions. Secretory IgA provides the first line of defense against local infections and is important in processing food antigens in the gut.

DIF: 1

REF: 156

12. Which immunoglobulin may be associated with lymphocyte differentiation? a. IgM b. IgA c. IgG d. IgD ANS: D

The main function of IgD is not known. However, it is believed to be involved in lymphocyte differentiation.

DIF: 1

REF: 156

13. Which immunoglobulin is associated with the physiological manifestations of allergy? a. IgG b. IgA c. IgE d. IgM ANS: C

IgE is normally present in very low concentration in the blood stream and has been very closely associated with allergy symptoms.

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DIF: 1

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REF: 156

14. IgG is known to fix complement, which aids in the lysis or elimination of foreign

materials. Molecules in the IgG subclasses differ in their ability to fix complement.

Which IgG subclass is the most active in complement fixation? a. IgG-1 b. IgG-2 c. IgG-3 d. IgG-4 ANS: C

IgG-3 has been found to be the most active in complement fixation. IgG-3 is followed by IgG-1, IgG-2, and IgG-4.

DIF: 1

REF: 156

15. Considering the noncovalent forces that contribute to antigen and antibody attraction,

________ are the strongest and most important contributors to antigen and antibody attraction, whereas ________ are the weakest contributors to this attraction. a. electrostatic forces, van der Waals forces b. hydrogen bonds, electrostatic forces c. van der Waals forces, hydrogen bonds d. electrostatic forces, hydrogen bonds ANS: A

The electrostatic forces between charged polar groups can create a strong attraction and are considered to be the strongest noncovalent attractive forces between antigens and antibodies. Hydrogen bonds are weaker than electrostatic forces. However, the numbers of hydrogen bonds cause these attractive forces to play a significant role in antigen and antibody interaction. Van der Waals forces are very weak and are only functional over small distances.

DIF: 2

REF: 157

16. When comparing an IgG molecule with a Fab fragment obtained from the same clonal

population, the affinity for the antigen of interest would be ________, and the avidity of the two for the antigen of interest would be ________. a. greater for the Fab fragment, the same b. the same, greater for the IgG molecule c. greater for the IgG molecule, greater for the Fab fragment d. the same, greater for the Fab fragment ANS: B

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Affinity refers to the strength of the binding of a single antibody-binding site and its corresponding antigenic determinant. Avidity refers to the overall binding of one antibody molecule to the corresponding antigen and includes the sum of binding sites for the whole antibody molecule. Thus the Fab fragment and the IgG molecule would have the same affinity for the antigen, but the IgG molecule would have a greater avidity because it has two binding sites, whereas the Fab fragment has only one binding site.

DIF: 2

REF: 157-158

17. In the laboratory analysis for amphetamine using antigen and antibody interactions as the

basis for measurement, there is concern of cross-reactivity with the over-the-counter drug pseudoephedrine. What is the basis for this concern? a. Pseudoephedrine may have a similar antigenic determinant site as amphetamine, since their chemical structures have some similarity. b. Pseudoephedrine may block the weak, noncovalent forces that operate between antigen and antibody. c. Pseudoephedrine may react with amphetamine to produce a product that is not recognized by the antibody. d. Pseudoephedrine and amphetamine will not fit into the antibody-binding site at the same time.

ANS: A

The concern is that amphetamine and pseudoephedrine may carry a similar antigenic determinant site. Although the antibody reactivity with amphetamine may be very high, the antibody may cross-react with pseudoephedrine, resulting in a falsely elevated result for amphetamine.

DIF: 2

REF: 158

18. Considering the precipitation curve shown in Figure 7-5, which phase could result in

reporting falsely low results? a. the antibody excess phase b. the antigen-antibody equivalence phase c. the antigen excess phase d. none of the above; all phases would result in accurate laboratory analysis ANS: C

As the amount of antigen increases beyond the amount of antibody present to bind to the antigen, the precipitation curve turns downward. This is because the cross-linking of the lattice network decreases when there is enough antigen to bind with each antibodybinding site separately.

DIF: 2

REF: 159

19. In gel precipitation methods, the rate of diffusion is ________ to molecular size and

_______ to concentration. a. inversely proportional, inversely proportional b. directly proportional, inversely proportional

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c. inversely proportional, directly proportional d. directly proportional, directly proportional ANS: C

The rate of diffusion is inversely proportional to the molecular size, because the larger molecules will diffuse more slowly through the gel. The rate of diffusion is directly proportional to the concentration.

DIF: 1

REF: 160

20. In radial immunodiffusion, calibrators of known concentration are analyzed along with

the patient sample to allow for the quantification of antigens as illustrated in Figure 7-9.

Suppose the diameter of the precipitation ring for the highest calibrator was less than the diameter for the next highest calibrator. Which of the following statements describes the likely cause for this problem? a. The incubation temperature was not kept constant. b. The concentration of the antibody in the gel was too high for the concentration of the highest calibrator. c. Because the concentration of the highest calibrator is so high, diffusion through the pores of the gel was restricted. d. The concentration of the highest calibrator was greater than the concentration of the antibody in the gel.

ANS: D

The concentration of the antigen in the highest calibrator exceeded the concentration of the antibody in the gel, causing a downturn in the precipitation curve, as illustrated in Figure 7-9, where the antigen is in excess. As a result, the cross-linking of the lattice network which causes precipitation decreases because in the highest concentration calibrator, there is enough antigen to bind with each antibody-binding site separately.

DIF: 3

REF: 161, Figure 7-9

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