title: A biological role for the major histocompatibility antigens.
abstract: A central function of the major histo-compatibility (H) antigens may be to signal changes in self to the immune system.  Virus-induced modification of strong transplantation antigens apparently results in recognition by thymus-derived lymphocytes (T cells), with subsequent clonal expansion and immune elimination of cells bearing non-self determinants. The extreme genetic polymorphism found in the major H antigen systems of higher vertebrates may reflect evolutionary pressure exerted by this immunological surveillance mechanism.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002999:Clone Cells / Q000276:immunology; D000939:Epitopes; D005796:Genes; D005815:Genetic Code; D006680:HLA Antigens; D006579:Heterozygote; D006649:Histocompatibility Antigens; D006720:Homozygote; D007111:Immunity, Cellular; D051379:Mice; D011110:Polymorphism, Genetic; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D014777:Virus Diseases / Q000235:genetics / Q000276:immunology
chemical_list: D000939:Epitopes; D006680:HLA Antigens; D006649:Histocompatibility Antigens