FcγRIIb/CD32B (human, recombinant)

FcγRIIb, also known as CD32B, is a low-affinity IgG receptor that binds the Fc region of IgG.^1,2 It is composed of two immunoglobulin-like (Ig-like) extracellular domains, a transmembrane domain, and a cytoplasmic tail domain containing an immunoreceptor tyrosine-based inhibitory motif (ITIM), which is important for its signaling activity.² The FcγRIIb isoform is generated via alternative splicing and has a shorter cytoplasmic tail than the FcγRIIa isoform, which allows the FcγRIIb isoform to be endocytosed. FcγRIIb is predominantly expressed on myeloid-derived cells, whereas the FcγRIIa isoform is primarily expressed on B cells. FcγRIIb is a co-inhibitory receptor that, when phosphorylated at the ITIM region, inhibits the activation of activating FcγRs on myeloid cells and of B cell receptors but can also inhibit B cell receptor activation in the absence of ITIM phosphorylation. It inhibits the pathogen clearing activity mediated by activating FcγRs, including reducing phagocytosis and cytokine release by myeloid cells, and reduces immune complex-mediated cellular activation, such as inhibiting B cell activation or inducing apoptosis of self-reactive B cells.¹ A SNP in FCGR2B, the gene encoding FcγRIIb, is associated with susceptibility to systemic lupus erythematosus (SLE), and SNPs in FCGR2B are also associated with rheumatoid arthritis and immune thrombocytopenic purpura (ITP).³ Cayman's FcγRIIb/CD32B (human, recombinant) protein can be used for binding assay applications. This protein consists of 183 amino acids and has a calculated molecular weight of 20.8 kDa. By SDS-PAGE, under reducing conditions, the apparent molecular mass of the protein is approximately 29 kDa due to glycosylation.

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1. Espéli, M., Smith, K.G.C., and Clatworthy, M.R. FcγRIIB and autoimmunity. Immunol. Rev. 269(1), 194-211 (2016).

2. Roghanian, A., Stopforth, R.J., Dahal, L.N., et al. New revelations from an old receptor: Immunoregulatory functions of the inhibitory Fc gamma receptor, FcγRIIB (CD32B). J. Leukoc. Biol. 103(6), 1077-1088 (2018).

3. Zhu, X.-W., Wang, Y., Wei, Y.-H., et al. Comprehensive assessment of the association between FCGRs polymorphisms and the risk of systemic lupus erythematosus: Evidence from a meta-analysis. Sci. Rep. 6, 31617 (2016).