Mapping of the class II region of the human major histocompatibility complex by pulsed-field gel electrophoresis.

The class II region of the human major histocompatibility complex (MHC) encodes a polymorphic set of cell surface glycoproteins involved in the regulation of the immune response. Each glycoprotein is a heterodimer composed of a alpha-chain of relative molecular mass (Mr) 34,000 (34 K) and a beta-chain of Mr = 28K. The products of the class II region have been characterized by the mixed lymphocyte reaction, serology, primed lymphocyte typing and DNA cloning. DR, DQ and DP, three subregions containing both alpha- and beta-chains, and two additional loci, DZ alpha and DO beta, locate this gene cluster on the short arm of chromosome 6. The precise genomic organization of these loci have been difficult to determine. Here we describe the use of pulsed-field gel electrophoresis together with restriction endonucleases having few genomic restriction sites and Southern blotting, to determine the order of the subregions and to derive a map for the human class II region. The order of these loci is similar to that of the homologous loci in the murine class II region. Our study establishes the use of pulsed-field gel electrophoresis in mapping large regions of the genome in higher eukaryotes.