FCGR2B

FCGR2B, also known as CD32b, is a protein encoded by the FCGR2B gene. It is a member of the immunoglobulin (Ig) superfamily and belongs to the Fc receptor family. Fc receptors are a group of cell surface receptors that bind to the Fc portion of antibodies. FCGR2B is a low-affinity receptor that binds to IgG antibodies. It is expressed on various immune cells, including B cells, macrophages, neutrophils, and dendritic cells.

The primary function of FCGR2B is to regulate immune responses. It acts as an inhibitory receptor, meaning that when it binds to an antibody-coated target, it can dampen or block immune cell activation. This is particularly important in preventing excessive immune responses that could lead to autoimmune diseases. On B cells, FCGR2B engagement can inhibit B cell activation, proliferation, and antibody production. This plays a crucial role in maintaining B cell tolerance.

In contrast to some other Fc receptors that trigger immune cell activation, FCGR2B typically delivers an inhibitory signal. This signal is mediated through ITIM (immunoreceptor tyrosine-based inhibitory motif) sequences within its intracellular domain, which recruit phosphatases that dephosphorylate signaling molecules. Dysregulation of FCGR2B function has been implicated in various autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis, where its impaired inhibitory capacity may contribute to autoantibody production and immune complex-mediated inflammation. Understanding FCGR2B's role is vital for developing targeted therapies for these conditions.