Exam 4: Antigen Recognition by B-Cell and T-Cell Receptors

The antibody surface involved in antigen binding varies depending on the size and nature of the antigen. This surface can be concave or flat, and sometimes, can have extended protrusions. This is accomplished by:

The drawing in Figure shows antibodies bound to repetitive epitopes on the surface of a bacterial pathogen. Even though all of these epitopes are identical, not all of them have antibodies bound to them. Figure The most likely explanation for this failure of antibodies to bind to every possible epitope on the surface of the pathogen is:

Hepatitis C is a virus that infects hepatocytes, which are non-immune cells of the liver. Currently, patients with chronic Hepatitis C infections are treated with repeated administration of type I interferon, predominantly interferon $\alpha$ . One aspect of this treatment that might aid the patient's immune system in clearing this virus infection is:

One strategy for vaccine development currently under investigation is the use of pathogen-derived T cell epitopes as a component of the vaccine. For viral pathogens, implementing this strategy involves scanning the predicted amino acid sequences of the viral proteins for likely peptide epitopes that would bind to MHC class I and MHC class II molecules. In addition to the complication of MHC sequence polymorphism in the human population, another complication of this strategy for peptide epitopes that would bind to MHC class II proteins is:

$\alpha$ : $\beta$ TCRs generally have a binding preference for either peptide:MHC class I or peptide:MHC class II complexes. However, on occasion, one $\alpha$ : $\beta$ TCR might actually be able to recognize either class of peptide:MHC complexes. When such an $\alpha$ : $\beta$ TCR is expressed on a CD4 T cell, it will only activate its T cell after binding to peptide:MHC class II complexes. Why is this the case?

The innate immune response together with antibodies are generally not effective at clearing infections established by pathogens that replicate inside host cells. The evolution of T cells has provided a means for the immune response to 'see' intracellular infections based on the ability of T cells to:

Both MHC class I and MHC class II molecules are highly polymorphic genes in the human population, with tens to hundreds of different alleles co-existing in the population. This means that a comparison of the MHC protein sequences between two individuals would reveal amino acid differences between one individual and the next. However, these amino acid differences are not randomly distributed along the entire protein, but are clustered in certain locations. The diagram in that most correctly indicates the regions of greatest variability between different MHC proteins (shown by the red highlights) is:

Antibody heavy and light chain polypeptides consist of repeated domains, each of which is ~110 amino acids and folds up into a compact three-dimensional structure known as an 'immunoglobulin domain.' These immunoglobulin domains are: