Germinal Center B Cells Are Essential for Collagen-Induced Arthritis

Objective. Rheumatoid arthritis (RA) is considered to be a prototypical autoimmune disorder. Several mechanisms have been proposed for the known pathologic function of B cells in RA, including antigen presentation, cytokine secretion, and humoral immunity. The aim of this study was to address the function of B lymphocytes in experimental arthritis. Methods. We mapped the adaptive immune response following collagen-induced arthritis (CIA). We subsequently monitored these responses and disease outcomes in genetically modified mouse strains that lack mature B cell or germinal center (GC) functionality in a B cell-intrinsic manner. Results. Following primary immunization, the draining lymph nodes broadly reacted against type II collagen (CII) with the formation of GCs and T cell activation. Mice that lacked mature B cell function were fully protected against CIA and had a severely attenuated ability to mount isotype-switched humoral immune responses against CII. Almost identical results were observed in mice that were selectively deficient in GC responses. Importantly, GC-deficient mice were fully susceptible to collagen antibody-induced arthritis. Conclusion. We identified GC formation and anticollagen antibody production as the key pathogenic functions of B cells in CIA. The role of B cells in RA is likely to be more complex. However, targeting the GC reaction could allow for therapeutic interventions that are more refined than general B cell depletion.