Parameters determining the efficacy of CD32 to inhibit activation of FcεRI in human basophils

Abstract

The conditions needed to readily observe the role of CD32 in modulating IgE-mediated secretion are enumerated and include consideration of IgG subclass, with a possible emphasis on IgG3, antibody:antigen ratios, but with no evidence that polymorphic variants of CD32 influence its function.

Figure 1

Inhibition of antigen-induced release by human IgG subclass antibodies. Each panel examines one of the three human IgG subclass anti-NP antibodies using the protocol described in the text and in the online repository. The plots in panels A, C, and E are a composite of two reaction conditions with different replication numbers. At 43 nM (3 μg/ml) NP-BSA, 3 times as much antibody was used as the next highest concentration of NP-BSA, 14 nM (1 μg/ml) (to maintain the same Ab:Ag ratio). Otherwise, the concentration of subclass antibody was held constant for all NP-BSA concentrations ≤ 14 nM. For IgG1 (panel A), the Ab concentrations were 24 nM (n=2) and 8 nM (n=5), for IgG2 (panel B), the Ab concentrations were 23 nM (n=13) and 7.7 nM (n=7), for IgG3 (panel C) the Ab concentrations were 2.5 nM (n=13) and 0.83 nM (n=8). For each panel, (●) response to NP-BSA without subclass antibody, (○) response with subclass antibody, (■) response with subclass antibody and Ab10523 at 50 μg/ml. The asterisks indicate a statistically significant difference (p<0.05) between subclass antibody ± Ab10523. Panels B, D, and F: reversal of human IgG subclass inhibition by the combination of blocking antibodies to CD32b and CD32a. Panel G; cells were stimulated with 14 nM NP-BSA (1 μg/ml) and the concentration of subclass IgG varied (n=3). (●) IgG1, (○) IgG2, (■) IgG3. Panel H; reversal of inhibition by the inclusion of Ab10523 at 50 μg/ml for each of the curves shown in panel G.