In contrast, only five assays detected unspecific signal in RA samples that were RF negative (n= 23), with five detecting IgM and one detecting IgG (test D: IgM 1/23; test F: IgM 1/23; test M: IgM 2/23, IgG 2/23; for test N: IgM 1/23; for test O: IgM 1/23) (Figures 2 and 3, Table S1 for details). Here, CD40LG is linked to rheumatoid arthritis.