In vitro antigen-specific IgE response is refractory to suppression by interferon-gamma

Although interferon (IFN)-gamma has been shown to be involved in the down-regulation of polyclonal IgE response in murine B cells that were activated by lipopolysaccharide (LPS) and interleukin 4 (IL4), effects of IFN-gamma on antigen-specific IgE responses have not been fully investigated. We have developed the following culture systems for inducing antigen-specific IgE responses in murine lymphocytes, and examined the effects of IFN-gamma on the following responses in vitro. (1) Anti-trinitrophenyl (TNP) IgE response induced by the stimulation with TNP-keyhole limpet hemocyanin (KLH) of BALB/c spleen cells that had been primed in vivo with the same antigen. (2) Anti-TNP IgE response induced by the coculture of unprimed C3H B cells with conalbumin (CA)-specific helper T cell clone, D10.G4.1, in the presence of TNP-CA. The former anti-TNP IgE response was not suppressed, and the latter suppressed only partially (less than 30%) by the addition of 100-200 U/ml IFN-gamma. In contrast, polyclonal IgE response in murine B cells that were stimulated by LPS and IL4 was abolished by 10 U/ml IFN-gamma. These results indicate that IgE production from antigen-stimulated B cells, in contrast to those activated polyclonally, are refractory to direct suppression by IFN-gamma.