CD32b

CD32B, also known as Fc gamma receptor IIb (FCGR2B), is a receptor in the Fc gamma receptor family that binds the Fc region of IgG antibodies. The FCGR2B gene encodes this receptor and is part of the FCGR gene cluster on chromosome 1. The receptor is expressed on B cells and certain myeloid cells.

It is a transmembrane protein with an immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytoplasmic tail, enabling inhibitory signaling by recruiting phosphatases such as SHIP and SHP-1. Functionally, CD32B acts as a negative regulator of B cell activation and antibody production when engaged by immune complexes, helping to maintain tolerance and prevent autoimmunity.

Clinical and research relevance is tied to its role in modulating humoral immune responses. Variants in FCGR2B have been linked to autoimmune disease risk, including systemic lupus erythematosus, and to variability in responses to monoclonal antibody therapies. Expression levels of CD32B can influence the strength of B cell–mediated responses and may be affected by cytokines, activation states, and genetic variation. The receptor’s activity is also considered in studies aiming to optimize IgG-based therapeutics, where Fc receptor interactions impact efficacy and safety.