A NEW SET OF MONOCLONAL-ANTIBODIES AGAINST HUMAN FC-GAMMA-RII (CD32) AND FC-GAMMA-RIII (CD16) - CHARACTERIZATION AND USE IN VARIOUS ASSAYS

Four mouse anti-human Fc gamma RII (CD32) (6C4, 2B2, 3D3, 93.4) (IgG1, kappa) and one anti-human Fc gamma RIII (CD16) (7.5.4) (IgG1, kappa) MAbs were raised. An in vitro switch variant, 7.5.4Sw50 (IgG2b, kappa) , was also derived from the 7.5.4 MAb. 6C4, 2B2, and 3D3 MAbs bind bot h Fc gamma RIIa and Fc gamma RIIb isoforms. Two of them (6C4 and 2B2 M Abs) allow a complete blockade of the binding of immune complexes to F c gamma RII. All three MAbs immunoprecipitate the receptor and bind bo th its glycosylated and nonglycosylated forms. The fourth anti-Fc gamm a RII MAb, 93.4, directed against the intracellular region of Fc gamma RIIa(1/2), allows its detection by Western blotting only when it is n ot phosphorylated. The 7.5.4 MAb binds both Fc gamma RIIIa and Fc gamm a RIIIb, can be used in Western blotting and does not inhibit aggregat ed IgG binding. ELISA using IV.3 (anti-Fc gamma RIIa(1/2))/6C4 and 3G8 (anti-Fc gamma RIIIa/b)/7.5.4Sw50 MAb pairs make it possible to detec t soluble Fc gamma RIIa(1/2) and Fc gamma RIII, with a sensitivity of 200 pg/mL and 1 ng/mL, respectively. Surface plasmon resonance analyse s indicated that the K-D of two of the three anti-Fc gamma RII and of the anti-Fc gamma RIII are in the same order of magnitude (6C4: 0.78 n M, 2B2: 0.28 nM, 7.5.4: 0.47 nM). The anti-Fc gamma RII 3D3 MAb exhibi ts an off-rate constant higher than the 6C4 and 2B2 MAbs and a K-D of 2.19 nM.