title: Complement genes of the major histocompatibility complex (complotypes), extended haplotypes and disease markers.
abstract: The human major histocompatibility complex (MHC)-linked genes C2,BF,C4A,C4B occur in populations and segregate in families as single genetic units or complotypes. Analysis for significant three-point linkage disequilibrium between HLA-B, DR and complotype on normal caucasian chromosomes 6p yields about a dozen haplotypes that account for most of the known HLA-B/HLA-DR linkage disequilibrium pairs previously noted in normal caucasian populations. We refer to the HLA-B/DR/complotype sets with significant linkage disequilibrium as extended haplotypes since they often show limited variation at other MHC-linked loci. From the study of MHC haplotypes in 21-hydroxylase deficiency, C2 deficiency and type 1 diabetes, it is becoming apparent that it is extended haplotypes rather than their individual alleles that are markers for these MHC-associated diseases.
mesh_terms: D000312:Adrenal Hyperplasia, Congenital / Q000235:genetics*; D000483:Alleles; D003175:Complement C2 / Q000172:deficiency*; D003165:Complement System Proteins / Q000235:genetics*; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics*; D008040:Genetic Linkage; D006801:Humans; D008285:Major Histocompatibility Complex; D044465:White People
chemical_list: D003175:Complement C2; D003165:Complement System Proteins