Studies on in vitro IgE synthesis from lymph node cells of mice during infection with Nippostrongylus brasiliensis. Presence of inhibitory factor(s) in serum.

The effect of serum factors on Ig synthesis (IgE, IgG) in vitro was analyzed. Spleen and mesenteric lymph node cells were obtained from Nippostrongylus brasiliensis-infected and non-infected mice. Sera and ammonium sulphate precipitated serum fractions from mice of different genetic origin (Balb/c - H-2d, A.CA - H-2f, B10.G - H-2q) suppressed in vitro IgE synthesis whereas a pronounced enhancement of IgG antibody synthesis was obtained in several experiments. Our results obtained with sera from both high and low IgE responder strains demonstrated that no strain specificity exists as to the inhibitory efficacy of mouse sera for total IgE synthesis in vitro. The suppressive activity of the mouse sera was concentrated in a fraction precipitated with 20%-50% saturated ammonium sulphate. Amicon XM50 ultrafiltration suggested that this fraction had an apparent molecular weight greater than 50,000 daltons. Suppressive activity was removed by immunoadsorption of the 20-50% fraction with anti-IgE Sepharose. After exogenous addition of monoclonal IgE to an inactive fraction in vitro neither the fraction enriched in IgE nor monoclonal IgE alone were able to suppress IgE synthesis in the culture. Our results suggest that one or more serum factors in the presence of IgE are responsible for the suppression of total IgE synthesis in vitro.