Question

MHC polymorphisms tend to cluster _____

A. in the peptide-binding groove.
B. in the transmembrane domain.
C. in the coreceptor contact residues.
D. in the framework region.
E. All of the above

Answer 1

MHC polymorphisms predominantly cluster in the peptide-binding groove of MHC molecules which is involved in antigen presentation to T cells, making answer A the correct choice.

Step-by-step explanation:

The student's question pertains to the localization of MHC polymorphisms within the structure of MHC molecules. These polymorphisms tend to cluster in specific areas that are crucial for their function of presenting antigens. Both MHC class I and MHC class II are complex structures, and the peptide-binding groove is where they bind antigens to be presented to T cells.

For MHC I, the antigen-binding cleft is made up of the α1 and α2 domains. Meanwhile, MHC II molecules have the antigen-binding cleft formed by the α1 and Β1 domains. Due to the critical role of these regions in antigen presentation, polymorphisms cluster specifically in the peptide-binding groove, which is integral to the immune response, as it determines what peptides can be presented and, therefore, recognized by T cells.

While the transmembrane domain, coreceptor contact residues, and framework regions are also parts of MHC molecules, they are not where the most extensive polymorphism is observed. Therefore, the correct response to the student's question is A. in the peptide-binding groove.