Anti-Mouse CD16.2 (Clone 9E9) - Purified <i>in vivo </i>GOLD™ Functional Grade (C859-GRP)

Fcγ receptors are the primary mediators of IgG effector responses, and individual Fc receptors (FcR) have different affinities for different IgG subclasses1. Four FcγRs are present in mice2, and FcγRIV (FcγRL3, CD16.2) binds to IgG2a, IgG2b3, and IgE4, but not IgG1 or IgG33. FcγRIV is a high-affinity receptor for monomeric IgG2a and IgG2b and a low-affinity IgE receptor for both IgEa and IgEb, binding to aggregates but not monomers4. Additionally, IgE immune complexes can displace IgG2 from FcγRIV. Surface expression of FcγRIV requires γ chain coexpression in vitro and in vivo3. FcγRIV and the γ chain are upregulated on bone marrow-derived monocytes by IFN-γ and LPS and are downregulated by TGF-β and IL-4. According to surface plasmon resonance, 9E9 has strong reactivity to FcγRIV as well as low level binding to FcγRII and FcγRIII2. In vivo, 9E9 binds and blocks FcγRIII only when 9E9 first binds FcγRIV on the same effector cell, resulting in concurrent inhibition of FcγRIII and FcγRIV. Native 9E9 binds to FcγRII and FcγRIII via the Fc. 9E9 was produced by immunizing Armenian hamsters with an FcγRIV-IgG1 fusion protein consisting of the extracellular domain of FcγRIV fused to a mouse IgG1 Fc portion (D265A-variant deficient in Fc-receptor binding)3. Splenic B cells were then fused to a mouse fusion partner, and hybridoma clones were screened for binding to CHO-K1-FcγRIV cells expressing FcγRIV. Blocking studies with 9E9 show that FcγRIV is necessary for IgG2a and IgG2b mediated platelet clearance in vivo1. Additionally, blocking FcγRIV with 9E9 reduces B-cell depletion2. 9E9 also interferes with immune complex binding to FcγRIV3 and can block FcγRIII on macrophages and neutrophils2.