B lymphocyte alloantigens in the study of the genetic basis of rheumatoid arthritis.

In order to carry out tissue typing studies in patients with rheumatoid arthritis (RA), 116 sera from pregnant multiparous women were screened for cytotoxicity specific for B lymphocytes. It was possible to identify three sera (M55, M58, M87) which reacted specifically with B cells after absorption with platelets. Each appeared to have a different specificity which was presumed to correspond to an alloantigen marker on the lymphocyte surface. The frequency of these alloantigen markers on B lymphocytes was investigated in patients with classical or definite RA and in controls. One of these, M58, occurred in 32 out of 43 RA patients (74 - 4%) compared with 10 out of 37 controls (27%). This difference was highly significant (P less than 0 - 0005). The relative risk of developing RA is 7 - 85 times greater in those possessing alloantigen M58. The other two B cell alloantigens failed to show any association with RA. The association with M58 may indicate a significant genetic contribution to disease susceptibility in RA.