HL-A antigen, gene, and haplotype frequencies in Denmark.

Between 426 and 1,967 unrelated Danes have been HL-A typed for most presently known HL-A antigens of the LA (first), FOUR (second), and AJ (third) segregant series. Antigen, gene and haplotype frequencies with delta values are given. AJ series antigens are most strongly associated with some of the FOUR series antigens, and except for one case, the linkage disequilibrium between AJ and FOUR does not seem to be influenced by the LA series; the exception concerns HL-A9, RH-315, and 12: the RH-315 determinant is significantly more frequent on HL-A9, 12 haplotypes and on other HL-A12 carrying haplotypes. The term "superhaplotype" is suggested for gene constellations such as the HL-A9, RH-315, 12 "haplotype". It is suggested that the associations between cross-reacting antigens from one series with the same antigen from another series may reflect recent evolutionary divergence of the cross-reacting antigens.