Relationship between IgE and platelet function

Abstract

We investigated the binding form of IgE to platelets and the relationship between IgE and platelet function. When the paraformaldehyde (PFA)-fixed platelets were incubated with the IgE-protein from human myeloma (M-IgE), the platelet-associated IgE (PAIgE) of Glanzmann's thrombasthenic platelets was significantly less than that of healthy control. The binding of M-IgE to the healthy PFA-fixed platelets was in-hibited by the pretreatment of the platelets with monoclonal anti-GPIIb/IIIa complex antibody or Arg-Gly-Asp-Ser (RGDS), but not monoclonal anti-GP I b antibody or heat aggregated IgG. When the unfixed platelets which had been activated with PAF or ADP were incubated with the M-IgE, the PAIgE increased significantly. The increased PAIgE hardly effected on not only the platelet aggregation or platelet secretion but also the increase of [Ca²⁺]i by activation. These results suggest that IgE binds to not the Fc-receptor but the GPIIb/IIIa-related receptor on the platelet surface. This binding increases with the platelet activation, whereas the increased IgE dose not appear to effect on the platelet function.