Human class II major histocompatibility antigen β-chains are derived from at least three loci

Abstract

Class II antigens of the major histocompatibility complex (MHC) consist of two glycosylated, membrane-integrated polypeptide chains¹. These cell surface-expressed molecules are involved in several immunobiological events involving cell–cell interactions^2,3, most of which seem to require that genetically identical class II antigens, or other molecules controlled by the same region of the MHC, are expressed on the interacting cells⁴. The extensive genetic polymorphism of the class II antigens⁵ has rendered analyses in the human system of the number of non-allelic species of class II antigens difficult, although several laboratories have reported the existence of at least two types of human class II antigens^6–9. Here we present the results of experiments using restriction enzyme digestions and separation of DNA from individuals homozygous for the MHC followed by hybridization to human class II antigen α-^10,11 and β-^12–14 chain cDNA probes. While the α -chain probe gave only a single hybridization band, the various β -chain probes revealed a more complex pattern that is consistent with the existence of at least three separate β -chain genes or pseudogenes in the human MHC.