MODULATION OF ANTIGEN-INDUCED B-CELL AND T-CELL RESPONSES BY ANTIGEN-SPECIFIC IGE ANTIBODIES

Ag-specific IgE Abs not only mediate immediate hypersensitivity throug h mast cell activation, but also enhance in vitro Ag presentation and in vivo specific Ab responses in mice, To delineate the role of IgE Ab in the modulation of Ag-specific responses, spleen cells from OVA-sen sitized BALB/c mice were cultured together with OVA-specific IgE (or I gG isotypes). OVA-dependent proliferative responses and anti-OVA IgE p roduction were enhanced in the presence of anti-OVA IgE. A significant decrease in IFN-gamma secretion in OVA-stimulated cultures was observ ed in the presence of anti-OVA IgE, but no changes in IL-4 production were detected. Anti-OVA Ige isotypes or anti-TNP IgE showed no signifi cant effect on any of these Ag-dependent responses. Addition of anti-C D23 Ab abolished these effects of anti-OVA IgE. Further, OVA-sensitize d spleen cells from CD23-deficient mice responded to in vitro stimulat ion with OVA, but demonstrated no modulation by anti-OVA IgE. These re sults demonstrate that Ag-specific IgE not only augments Ag presentati on and T cell proliferation, but also alters the pattern of cytokine p roduction and increases specific IgE synthesis, These modulatory effec ts of Ag-specific IgE appear to be mediated by binding to Fc epsilon R II/CD23.