MHC-LINKED CLASS-III GENES - ANALYSIS OF C-4 GENE-FREQUENCIES, COMPLOTYPES AND ASSOCIATIONS WITH DISTINCT HLA HAPLOTYPES IN GERMAN CAUCASIANS

The class III complement components, C4, C2 and factor B (BF), are encoded in the human major histocompatibility complex (MHC). The 2 genes determining C4 (C4A and C4B) display considerable polymorphism and, thus, are important markers for HLA. In combination with alleles of C2 and BF they can be grouped into unique complotypes. The C4 alleles in a panel of 204 unrelated German Caucasians were analyzed; their segregation with HLA haplotypes in 24 normal families were studied. Inclusion of the class III markers with the class I and II alleles provides a more refined picture of the genetic structure of the MHC in these families. When charted accordin to the HLA-B locua specificities the MHC can be clustered into groups showing distinctly homogenous or heterogenous complotypes. The identification of such groups is valuable for the selection of genetic material to analyze the molecular genetics of the human MHC.