Page 318 - Veterinary Immunology, 10th Edition

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FIG. 11.10 Heterozygous animals with two MHC alleles at each
locus express six different antigen-presenting molecules on the cell
surface. Therefore, they generate a more diverse and effective
immune response than homozygous animals with only a single
allele, at each locus. An example of heterozygote advantage.

MHC polymorphism is maintained in populations by a process
called overdominant selection or heterozygote advantage. Simply

put, MHC heterozygotes are at an advantage because they can
respond to a greater range of microbial antigens and so are best
fitted to survive infectious diseases. The antigen-binding sites of
MHC class Ia or II molecules are also very nonspecific, and it has
been estimated that an average MHC molecule can bind about 2500

different peptides. This is because the MHC groove binds to the

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