BCR and rheumatoid arthritis: Unlike other treatments that focus on blocking specific cytokines, disrupting DAP12, and by extension, SYK which has also been shown to be up-regulated in RA [52, 53] and affects the action of receptors important for other immune cells such as B-cell receptors (BCR) and Fc receptors (FcR) on mast cells, macrophages, B cells and T cells [25].