B-cell receptor and Fc-gamma receptor IIb (BCR/FcγRIIB)

The B-cell receptor (BCR) and the Fc-gamma receptor IIb (FcγRIIB) are integral membrane proteins that coordinately regulate B-cell activity. The BCR complex, comprising membrane-bound immunoglobulin and the CD79a/CD79b heterodimer, is responsible for antigen recognition and the initiation of pro-inflammatory signaling cascades (Source: StatPearls). In contrast, FcγRIIB (CD32B) is the sole inhibitory Fc receptor expressed on B cells, functioning as a molecular brake that terminates BCR-induced activation when it binds to the Fc portion of IgG in immune complexes (Source: UniProt P31994). This inhibitory mechanism involves the recruitment of the SH2 domain-containing inositol 5-phosphatase (SHIP-1), which antagonizes the PI3K pathway. Therapeutic strategies, such as the development of obexelimab, leverage this natural feedback loop by co-engaging the BCR (often via the CD19 co-receptor) and FcγRIIB to suppress pathogenic B-cell functions in autoimmune diseases like systemic lupus erythematosus (Source: Zenas BioPharma). Dysregulation of these receptors is also a hallmark of various B-cell malignancies and chronic inflammatory conditions.

Other names

BCR and CD32BB-cell receptor complex and Fc receptorCD19/FcγRIIB co-engagement target

Co-engagement of the B-cell receptor (or its co-receptor CD19) and the inhibitory Fc-gamma receptor IIb (FcγRIIB) to suppress B-cell activation through the recruitment of phosphatases like SHIP-1 (Source: PubMed: 26403174).