Effect of seasonal ragweed exposure on immunoglobulin E antiragweed antibodies in cultures of peripheral mononuclear cells, plasma and nasal secretions. 
To determine the effects of seasonal ragweed exposure on in vitro IgE antibody production, the antiragweed IgE antibody content of 7-day cultures of peripheral blood mononuclear cells was assessed in samples obtained before, during and after the ragweed season, in 4 ragweed-allergic and 11 nonallergic individuals.  The levels of ragweed-specific IgE and total IgE in unstimulated culture supernatants were measured by solid phase radioimmunoassays.  Antiragweed IgE antibody was apparently detectable in the 7-day culture supernatants of both allergic and nonallergic individuals, and the antibody concentrations increased after natural ragweed exposure.  However, the bindable counts of IgE antibody in supernatants from allergic patients were inhibited by soluble ragweed antigen, while those from nonallergics were not inhibitable, suggesting that supernatants from nonallergics did not contain true ragweed-specific IgE antibody.  Because, for most subjects, the quantity of IgE in culture supernatants from 7-day cultures of living cells was the same as that derived from cells which were either frozen and thawed prior to culture, or briefly exposed to pH 3.7 buffer, the majority of IgE antibody in supernatants from allergic subjects, and of total IgE in supernatants from all subjects, was apparently not newly synthesized, but was preformed, and appeared to be largely derived from the cell surface.  IgE antiragweed antibody was detected in the nasal secretions and plasma of allergic, but not nonallergic individuals, and the levels of antibody in allergic subjects increased after seasonal exposure.  The fraction of total IgE protein accounted for by IgE antiragweed antibody in nasal secretions collected postseasonally was higher than that in both culture supernatants and plasma, suggesting that ragweed-specific IgE antibody is synthesized locally in the nose.