Question 1

Antibodies are ______ that are produced by the _______.

Accepted Answer

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

Question 2

Which immunoglobulin exists primarily as a pentamer and is the predominate immunoglobulin in the initial immune response to an antigen?

Accepted Answer

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.

Question 3

The most potent antigens are macromolecules with molecular weights greater than:

Accepted Answer

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.

Question 4

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

Accepted Answer

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.

Question 5

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?

Accepted Answer

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.

Question 6

Considering the precipitation curve shown in Figure 7-5  in your textbook, which phase could result in reporting falsely low results?

Accepted Answer

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 antibody-binding site separately.

Question 7

The portion of the immunoglobulin molecule that binds to antigens is:

Accepted Answer

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

Question 8

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?

Accepted Answer

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.

Question 9

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 _______.

Accepted Answer

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.

Question 10

Which of the following antigenic determinants would be the most reactive?

Accepted Answer

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.

Question 11

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.

Accepted Answer

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.

Question 12

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.

Accepted Answer

All three components of the statement are correct.

Question 13

Haptens are:

Accepted Answer

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 low-molecular-weight component of the larger complex reacts with the antibody.Examples of haptens include lipids, hormones, and drugs.

Question 14

Which immunoglobulin can cross the placental membrane?

Accepted Answer

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

Question 15

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 ________.

Accepted Answer

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.

Question 16

Which immunoglobulin is associated with the physiological manifestations of allergy?

Accepted Answer

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

Question 17

Which immunoglobulin is the predominant immunoglobulin in body secretions such as saliva and sweat?

Accepted Answer

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.

Question 18

Which immunoglobulin may be associated with lymphocyte differentiation?

Accepted Answer

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

Question 19

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 in your text book.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?

Accepted Answer

The concentration of the highest calibrator being greater than the concentration of the antibody in the gel would lead to an excess of antigen over antibody, resulting in a smaller precipitation ring due to the antigen-antibody complexes being formed in suboptimal proportions. This phenomenon is known as the prozone effect, where high concentrations of antigen can lead to underestimation of the antigen amount because of insufficient antibody to form visible complexes throughout.

Question 20

Which of the following statements best describes the region of the immunoglobulin molecule that is responsible for specific binding to the antigen?

Accepted Answer

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.

Quiz 7: Immunological Reactions

Antibodies are that are produced by the _.