CD40LG and rheumatoid arthritis: In contrast to the antibody system against UH-RA.1, IgM was less redundant within antibodies against UH-RA.21: IgG and IgA were both twice as prevalent (IgM 35/158 [22 %] versus IgG 85/158 [54 %] and IgA 86/158 [54 %]) (Fig. 1d).