Coexistence of an MHC chromosomal segment marked by HLA B17,BfS,C4A6,B1,DR7, and DQw9 in different ethnic groups.

Previously we have shown that the supratype HLA B17 BfS C4A6 B1 DR7 (17 6 1 7) carrying a C4/Bgl II RFLP correlating with C4A6 coexists in whites and Thai/Chinese. Using conventional and PFGE/Southern blotting with class II, class III, and TNF probes as well as serologic DQ subtyping, we have extended these comparisons and now report that four examples each of white and Oriental 17 6 1 7 bear DQw9, as well as an approximately 10kb fragment hybridizing with a DR beta probe following digestion of genomic DNA with Hind III. Furthermore, Oriental and white 17 6 1 7 share a genomic insertion of some 70kb close to the class II region. These data suggest that 17 6 1 7 may mark a highly conserved chromosomal segment which provides new insights into the biology and evolution of the major histocompatibility complex.