Distribution and co-occurrence of MHC class I, II, and III markers in southern Chinese: implications for autoimmune disease.

A study of MHC class I, II, and III markers in a group of southern Chinese in Hong Kong is reported. HLA antigen frequencies and complement allele frequencies are given, together with statistically significant pair-wise co-occurrences. Over half of the statistically significant positive and negative linkage disequilibria relate to two extended haplotypes. These haplotypes, or components of them, are associated with a number of diseases in Chinese, particularly diseases of autoimmune origin. One haplotype, A2, Bw46, DRw9, appears to be an analogue of the haplotype A1, B8, DR3 which predisposes to similar diseases in Caucasians. The question is raised of why susceptibility to the same group of diseases in two different racial groups should be related to the haplotypes having the strongest linkage disequilibria within those racial groups.