Le complexe majeur d'histocompatibilité : recombinaison, pressions sélectives et évolution.

Abstract

Genes coding for the major histocompatibility complex (MHC) class I and class II molecules belong to relatively large multigene families. Most of these genes have been involved in immunological phenomena such as graft rejection, antivirus and anti- tumor immunity, T- and B lymphocyte collaboration and susceptibility to various diseases. All these functions seem to result from the unique capability of MHC class I and class II molecules to associate with hundreds of thousands of peptides derived from self or nonself proteins and to present these peptides to specific T cells. Selective pressure operating on MHC class I and class II molecules have selected recombination events causing major alterations of the MHC multigene families and, for some members of the family, sequence diversity among different alleles of the same locus. This genetic diversity makes the MHC one of the most polymorphic regions of the genome. Analysis of these polymorphisms is proving useful in unravelling the origin of the human species and the historical relationships between actual populations.