CD40LG and rheumatoid arthritis: Apart from radiographic progression, significant association of IgA-RF with extra-articular manifestations was demonstrated in a study published already three decades ago revealing that 80 % of IgA-RF positive patients had one or more extra-articular RA complications, versus only approximately 20 % of IgA-RF negative patients with elevated IgM/IgG-RF who were not different from seronegative patients [56].