Molecular biology of the HLA class I and class II genes.

The human major histocompatibility complex (the HLA complex) encodes two classes of cell surface heterodimeric glycoproteins which regulate the immune response to foreign antigens. Molecular analysis of the HLA class I and class II genes has yielded considerable information about their organization and structure. The class I genes consist of the polymorphic A, B and C genes and the non-polymorphic Qa, Tla-like genes. The HLA class II region contains multiple alpha and beta genes and pseudogenes which map into three subregions: DR, DQ and DP. The class II genes share similar gene structures, but vary in their degree of polymorphism.