Question 1

Major histocompatibility (MHC)molecules containing beta-2-microglobulin:

Accepted Answer

MHC class I molecules, which contain beta-2-microglobulin, are determined by the HLA-A, HLA-B, and HLA-C genes.

Question 2

Antigens found in different species that trigger a similar antibody response are called:

Accepted Answer

Heterophile antigens are antigens found in different species that trigger a similar antibody response. Examples include the Epstein-Barr virus and sheep red blood cells, which both elicit the production of antibodies that cross-react with each other. Haptens are small molecules that are not immunogenic by themselves but can become immunogenic when they bind to carrier molecules. Alloantigens are antigens that differ between members of the same species, such as blood type antigens. Autoantigens are self-antigens that are recognized as foreign by the immune system in autoimmune diseases.

Question 3

Which of the following is a characteristic of HLA-DR,-DP,and -DQ molecules?

Accepted Answer

HLA-DR, -DP, and -DQ molecules are part of the major histocompatibility complex (MHC) class II and are expressed co-dominantly, meaning both maternal and paternal alleles are expressed in an individual.

Question 4

Class II molecules bind to what kind of peptides?

Accepted Answer

Class II molecules bind to processed exogenous peptides, which are derived from proteins that have been taken up from outside the cell and processed within the endosomal/lysosomal pathway.

Question 5

Which is characteristic of thymus-dependent antigens?

Accepted Answer

Thymus-dependent antigens are typically proteins, meaning choice A is the only correct answer. Choices B and C are incorrect, as thymus-dependent antigens are not mainly polysaccharides and do not stimulate primarily IgM.

Question 6

A low-molecular-weight molecule that has one binding site for an antibody would be which of the following?

Accepted Answer

A low-molecular-weight molecule that has one binding site for an antibody is called a hapten. A hapten is a small molecule that can bind specifically to an antibody, but is not immunogenic on its own. It requires binding to a carrier molecule (such as a larger protein) to elicit an immune response. Examples of haptens include small molecules like penicillin and urushiol, the allergenic compound found in poison ivy.

Question 7

T-independent antigens:

Accepted Answer

T-independent antigens do not require T cell help and therefore primarily stimulate an IgM response, not an IgG response. Additionally, they do not typically lead to a long-lasting memory response or anamnestic response.

Question 8

Which of the following is likely to be the most immunogenic?

Accepted Answer

Proteins are generally the most immunogenic of the options given, as they contain a wider variety of epitopes that can be recognized by the immune system. Lipids and nucleic acids are generally less immunogenic, as they do not contain as many recognizable epitopes. Polysaccharides can be immunogenic, but typically require conjugation to a carrier protein or other modifications to enhance their immunogenicity. Additionally, the molecular weight of the molecule is not necessarily indicative of its immunogenicity.

Question 9

Endogenous peptides binding to HLA-A,B,or C molecules on the surface of hepatocytes is critical for the response by:

Accepted Answer

Endogenous peptides binding to HLA-A,B, or C molecules on hepatocytes is critical for the response by cytotoxic T cells, as these cells can recognize and target the hepatocytes for destruction if they are infected or abnormal. B lymphocytes, T helper cells, and macrophages do not directly recognize or respond to peptides presented on HLA-A,B, or C molecules.

Question 10

The purpose of the invariant chain (Ii,CD74)is to block the peptide-binding site of:

Accepted Answer

The invariant chain (Ii,CD74) blocks the peptide-binding site of class II molecules, which are involved in presenting antigenic peptides to CD4 positive T cells. The blocking function of Ii helps prevent unwanted peptides from binding to class II molecules before they reach the endosomal compartment where they can properly bind and present antigens to T cells. Therefore, choice B is the correct answer. Ii does not impact the binding of antibody molecules or class I molecules to peptides, nor does it affect T cell receptors directly.

Question 11

Blood from a suspect is typed to see if it is a match with a sample found at the crime scene.The suspect's blood exhibits the following reactions: no agglutination with anti-A,no agglutination with anti-B.What is the suspect's blood type?

Accepted Answer

The lack of agglutination with both anti-A and anti-B indicates that the blood does not have A or B antigens, which is characteristic of type O blood.

Question 12

A macromolecule that is capable of eliciting an immune response in an immunocompetent host is called a(an):

Accepted Answer

An antigen is a macromolecule that can induce an adaptive immune response in an immunocompetent host. They are usually proteins, polypeptides, or large polysaccharides that are recognized by the immune system as foreign and stimulate an immune response. Antibodies are produced by the immune system in response to antigens, but they are not antigens themselves. Haptens are small molecules that are not capable of eliciting an immune response on their own but can do so when they bind to larger carrier molecules. Acute phase reactants are proteins that are produced by the liver in response to inflammation or infection, but they do not elicit an immune response.

Question 13

All of the following are characteristics of both MHC class I and class II molecules EXCEPT:

Accepted Answer

MHC class I molecules are expressed constitutively on all nucleated cells, while MHC class II molecules are only expressed on certain immune cells. A is correct, as both MHC class I and II are expressed codominantly. B is correct as both MHC class I and II are involved in antigen recognition. C is correct, as both MHC class I and II are members of the immunoglobulin superfamily.

Question 14

The ability to respond to antigen depends on which of the following factors?

Accepted Answer

The ability to respond to antigen is affected by multiple factors, including age, proper nutrition, and genetic predisposition. Therefore, all of the above factors are necessary for a proper immune response.

Question 15

Another name for antigenic determinant is:

Accepted Answer

Antigenic determinant is another name for an epitope, which is a small portion of an antigen that is recognized by the immune system and binds to antibodies or T cell receptors. Immunogen is a substance capable of inducing an immune response, antibody is a protein produced by the immune system that recognizes and binds to antigens, and polysaccharide is a type of carbohydrate. None of these terms are synonymous with antigenic determinant.

Question 16

Which MHC class of antigens is necessary for antigen recognition by CD4-positive T cells?

Accepted Answer

CD4-positive T cells recognize antigen in the context of MHC class II molecules. MHC class I molecules present antigens to CD8-positive T cells. MHC class III molecules encode complement and other immune-related proteins, but are not involved in antigen presentation.

Question 17

A 50 kDa protein from a bacterial cell that has numerous different epitopes would be called:

Accepted Answer

A 50 kDa protein with numerous different epitopes would be both immunogenic (able to elicit an immune response) and antigenic (able to bind specifically with antibodies or T-cells). Therefore, the best choice is D, immunogen and antigen.

Question 18

MHC class II molecules have specificity for:

Accepted Answer

MHC class II molecules have a peptide binding groove that is specific for peptides with a particular motif, known as the MHC class II binding motif. This motif includes specific amino acid residues that are necessary for binding to the MHC class II molecule. The specificity of the peptide-binding groove allows MHC class II molecules to present peptides from extracellular sources, such as bacteria and viruses, to CD4+ T cells.

Question 19

Which of the following molecules is the better immunogen?

Accepted Answer

Proteins are considered the most effective immunogens because they have a complex three-dimensional structure that allows for the presence of multiple epitopes (molecules recognized by the immune system) on a single molecule. This enhances the chance of stimulating an immune response. In addition, proteins have a wide range of molecular weights which allows immunogenicity in different regions of the body.

Question 20

The best immunogen would be:

Accepted Answer

A multivalent immunogen with many specificities can stimulate a stronger and more diverse immune response, making it a better immunogen.

Quiz 3: Nature of Antigens and Major Histocompatibility Complex

Major histocompatibility (MHC) molecules containing beta-2-microglobulin: