Figure 5.15. Allelic variation occurs at specific sites within MHC molecules.

Figure 5.15Allelic variation occurs at specific sites within MHC molecules

Variability plots of the amino acid sequences of MHC molecules show that the variation arising from genetic polymorphism is restricted to the amino-terminal domains (α1 and α2 domains of class I molecules, and α1 and β1 domains of MHC class II molecules). These are the domains that form the peptide-binding cleft. Moreover, allelic variability is clustered in specific sites within the amino-terminal domains, lying in positions that line the peptide-binding cleft, either on the floor of the groove or directed inward from the walls. For the MHC class II molecule, the variability of the HLA-DR alleles is shown. For HLA-DR, and its homologues in other species, the α chain is essentially invariant and only the β chain shows significant polymorphism.

From: The major histocompatibility complex and its functions

Cover of Immunobiology
Immunobiology: The Immune System in Health and Disease. 5th edition.
Janeway CA Jr, Travers P, Walport M, et al.
New York: Garland Science; 2001.
Copyright © 2001, Garland Science.

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