Generation of Cell‐Derived Factors Suppressing IgE Synthesis of Nippostrongylus brasiliensis‐Infected Mice in Vitro

Modulation of de novo IgE synthesis in vitro was studied using the parasitic infection of mice with the nematode Nippostrongylus brasiliensis. Cell-derived factors were generated by stimulation of splenic and mesenteric lymph node cells of BALB/c mice with monoclonal IgE in vitro. High molecular weight (greater than 50,000) and low molecular weight (less than 50,000) culture supernatants were prepared. De novo IgE synthesis of BALB/c lymphocytes--obtained from N. brasiliensis-reinfected mice that secreted pronounced quantities of IgE in vitro--was markedly reduced by the addition of high molecular weight supernatants. A dose-dependent suppression of IgE synthesis was obtained, whereas IgG synthesis, viability, and cell proliferation were not inhibited. After fractionation of low molecular weight supernatants with IgE-Sepharose the glycine/HCl eluate fractions markedly inhibited the in vitro IgE synthesis. Low molecular weight factors which suppressed IgE synthesis without modulating IgG production were obtained from IgE high responder B6D2F1 normal mouse cells. Thus, our results demonstrate the generation of IgE-specific suppressor factors in vitro upon stimulation with IgE. The suppression of IgE synthesis by eluate fractions of low molecular weight supernatants absorbed with IgE-Sepharose suggest a potential role for IgE binding factors on de novo IgE synthesis in vitro.