The association of DNA variants at or near the IgH locus with rheumatoid arthritis.

DNA samples from 78 patients with classical or definite rheumatoid arthritis (RA) and 132 healthy controls were analysed by the Southern blotting method, using two DNA probes: the first to the immunoglobulin mu heavy-chain switch region (S mu), in conjunction with the SstI restriction endonuclease, and the second to the D14S1 region, in conjunction with the HindIII restriction endonuclease. The homozygous phenotype for the 6.9 kb S mu fragment was decreased in the patient group (7.8%) compared to controls (19.1%) (P = 0.04). The homozygous phenotype for the 10.3 kb D14S1 fragment was increased in the patient group (38.5%) compared to controls (21.2%) (P = 0.02). The increase was more pronounced in the DR4-positive patients (51.2%) (P versus DR4-positive controls = 0.009). These results suggest that genes on chromosome 14 are involved in the genetics of RA.