CD79A and rheumatoid arthritis: •Serum anti-MAA Ab with limited RA specificity (IgG 80% positive in RA, 74% positive in OA & SLE, 14% positive in SpA)•IgA anti-MAA Ab higher in RA vs. other groups•Factors positively associated with anti-MAA Ab include race (IgA, IgG) and current smoking (IgA)