The Ia Antigens

Abstract

Histocompatibility loci determine polymorphic cell surface antigens capable of causing rejection of tissue grafts between animals which are genetically dissimilar at such loci. While the number of histocompatibility loci within any species is probably quite large (Bailey and Mobraaten, 1969), every mammalian species that has so far been examined possesses one such locus which has overwhelming importance in determining the fate of an allograft. This locus has been termed the “major histocompatibility complex” (MHC) (Bach, 1973), and within each species a particular system of nomenclature has been adopted. As an experimental model, the MHC of the mouse, known as the H-2 complex, is the best defined in terms of genetic fine structure. Four major regions of the H-2 complex have been defined and have been mapped linearly in the murine IXth linkage group (chromosome No. 17) in the order Κ--- I---S---D with respect to the centromere (Klein, 1970) of that chromosome.