The enormous variability in the MHC class I alleles in human populations is not randomly distributed but rather concentrated in specific regions of the protein. Areas of HIGHEST diversity include:

Amino acids in the alpha helices that interact with the antigens

Explanation:

The major histocompatibility complex (MHC) locus contains genes that encode proteins localized in the cell surface which play roles related to the interaction between host and antigen. The MHC locus encodes proteins that are localized on the surface of T cells and bind peptides derived from pathogens, this represents an initial phase of recognition and activates the immune system

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