Fc fragment of IgA receptor (CD89) (CD89)

The Fc fragment of IgA receptor (CD89), also known as FcαRI, is a type I transmembrane glycoprotein and a member of the immunoglobulin superfamily that specifically binds the Fc region of immunoglobulin A (IgA). It is predominantly expressed on cells of the myeloid lineage, including neutrophils, monocytes, macrophages, and eosinophils, where it serves as a critical link between the humoral and cellular immune systems. Upon binding to IgA immune complexes, CD89 associates with the ITAM-containing FcR gamma chain to trigger potent effector functions such as phagocytosis, antibody-dependent cellular cytotoxicity (ADCC), and the release of pro-inflammatory cytokines. In the context of modern immunotherapy, CD89-derived modules—specifically its transmembrane and signaling domains—are being utilized to engineer chimeric antigen receptors (CARs) for in vivo programming of myeloid cells to target solid tumors. Conversely, dysregulation of the IgA-CD89 axis is implicated in the pathogenesis of autoimmune and inflammatory conditions, such as IgA nephropathy and rheumatoid arthritis, making it a target for antagonistic therapeutic strategies. Drugs interacting with this target include bispecific antibodies and in vivo CAR-mRNA therapies designed to redirect innate immune cells against cancer, as well as antagonistic antibodies aimed at resolving chronic inflammation.

Other names

Fc alpha receptor IFcαRIFCARIgA Fc receptorCD89 antigen

CD89-targeted therapies function through two primary mechanisms: antagonism and recruitment. Antagonistic antibodies block the binding of IgA to CD89, thereby inhibiting the pro-inflammatory activation of neutrophils and macrophages in diseases like IgA nephropathy and rheumatoid arthritis. Alternatively, CD89-derived modules are used in bispecific antibodies and in vivo CAR therapies to cross-link the receptor with tumor-associated antigens, redirecting myeloid cells to perform antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis against cancer cells.