Increased frequencies of Sm and nRNP autoantibodies in American blacks compared to whites with systemic lupus erythematosus.

Frequencies of autoantibodies to Sm, nRNP, Ro (SSA) and La (SSB) were determined by countercurrent immunoelectrophoresis (CIE) and/or enzyme linked immunosorbent assays (ELISA) in 106 whites and 60 blacks with systemic lupus erythematosus. Anti-Sm occurred significantly more frequently in blacks (25%) than whites (10%) (p = 0.02), as did anti-nRNP (40% versus 23%; p = 0.03). By CIE, anti-Sm and/or nRNP occurred in 47% of blacks and 24% of whites (p = 0.004), and by ELISA the Sm/nRNP complex was detected in 52% of blacks versus 26% of whites (p = 0.003). Antibodies to Ro and La occurred with equal frequencies between the races.