A New Set of Monoclonal Antibodies Against Human FcγRII (CD32) and FcγRIII (CD16): Characterization and Use in Various Assays

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Abstract
Four mouse anti-human FcγRII (CD32) (6C4, 2B2, 3D3, 93.4) (IgG1,κ) and one anti-human FcγRIII (CD16) (7.5.4) (IgG1,κ) MAbs were raised. An in vitro switch variant, 7.5.4Sw50 (IgG2b,κ), was also derived from the 7.5.4 MAb. 6C4, 2B2, and 3D3 MAbs bind both FcγRIIa and FcγRIIb isoforms. Two of them (6C4 and 2B2 MAbs) allow a complete blockade of the binding of immune complexes to FcγRII. All three MAbs immunoprecipitate the receptor and bind both its glycosylated and nonglycosylated forms. The fourth anti-FcγRII MAb, 93.4, directed against the intracellular region of FcγRIIa1/2, allows its detection by Western blotting only when it is not phosphorylated. The 7.5.4 MAb binds both FcγRIIIa and FcγRIIIb, can be used in Western blotting and does not inhibit aggregated IgG binding. ELISA using IV.3 (anti-FcγRIIa1/2)/6C4 and 3G8 (anti-FcγRIIIa/b)/7.5.4Sw50 MAb pairs make it possible to detect soluble FcγRIIa1/2 and FcγRIII, with a sensitivity of 200 pg/ml. and 1 ng/mL, respectively. Surface plasmon resonance analyses indicated that the KD of two of the three anti-FcγRII and of the anti-FcγRIII are in the same order of magnitude (6C4: 0.78 nM, 2B2: 0.28 nM, 7.5.4: 0.47 nM). The anti-FcγRII 3D3 MAb exhibits an off-rate constant higher than the 6C4 and 2B2 MAbs and a KD of 2.19 nM.