Association of complement alleles C4AQ0 and C4B5 with rheumatoid arthritis in Koreans.

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Abstract
OBJECTIVE: To investigate the association of complement C4 allotypes with rheumatoid arthritis in Koreans. METHODS: 65 rheumatoid arthritis patients and 255 controls were typed for C4 allotypes and HLA-A, B, C, DR, and DQ antigens. RESULTS: The frequencies of C4AQ0 (32.3% v 14.9%, P < 0.005) and C4B5 (29.2% v 12.2%, P < 0.005) were significantly increased in rheumatoid arthritis patients compared with healthy control subjects. Among rheumatoid patients, the frequency of C4AQ0 was significantly increased in both the rheumatoid factor (RF) positive (27.3%) and the RF negative (66.7%) subgroups. The frequencies of C4B5 and HLA-DR4 were significantly increased only in RF positive subgroup. C4B5 was strongly associated with HLA-DR4, whereas C4AQ0 did not show association with DR4. CONCLUSIONS: In Koreans, C4AQ0 and C4B5 are associated with susceptibility to rheumatoid arthritis, as in the Japanese. C4B5 is strongly associated with HLA-DR4. C4AQ0 is considered to be a DR4 independent risk factor, and a disease susceptibility allele in linkage disequilibrium with C4AQ0 is suggested in Korean patients with rheumatoid arthritis.