Comparison of the EBNA-1 IgA and EBNA-1 IgM levels in the 77 RA patients sorted into IgM and IgA RF positives and negatives, respectively, revealed a significant difference between the two groups for both EBNA-1 IgM and IgA (P < 0.0001 and P = 0.0005, resp). This evidence concerns the gene CD40LG and rheumatoid arthritis.