HLA-C locus antigens in HLA-B27 associated arthritis.

Frequencies of the HLA-C locus antigens, Cw1, Cw2, Cw3, and Cw4, were determined in 88 patients with spondylitic diseases and 88 matched and 64 B27-positive normal controls. Both Cw1 and Cw2 were significantly increased in B27-positive patients and B27-positive controls as compared to B27-negative patients and matched controls. Cw1 and Cw2 demonstrate strong linkage disequilibrium with B27. Their absence in B27-negative patients suggests disease susceptibility is related to HLA-B.