In vitro production of IgE by human peripheral blood mononuclear cells. I. Rate of IgE biosynthesis

IgE protein and grass-specific IgE antibodies were detected in the supernatants of 7-day cultures of unstimulated and pokeweed mitogen (PWM) stimulated human blood mononuclear cells from non-atopic and grass pollen-sensitive individuals. Significant amounts of IgE protein were detected in culture supernatants of grass-sensitive individuals and, even at lower levels, in those of non-atopic subjects. In contrast, detectable amounts of grass-specific antibodies were found only in the culture supernatants of grass-sensitive subjects. The mean values of total and grass-specific IgE detected in the supernatants of unstimulated and PWM-stimulated cultures did not differ statistically. Time sequence studies showed that IgE concentrations, measured in the 7-day supernatants, were due to a continuous release from the cells of IgE quantities progressively decreasing up to days 7 or 8. Comparison of the IgE protein and IgE antibody found in the 7-day culture supernatants to those released from initial cell pellets by treatment with acid buffer or freezing and thawing, showed that the IgE detected in 7-day supernatants could result, in part, from the release of cytophilic IgE bound to basophil or other cell types and in part also from the release of preformed lymphocyte cytoplasmic IgE into the supernatant fluids during the course of culture. In most non-atopic subjects and in some grass-sensitive patients the preformed IgE accounted virtually for the total IgE detected in the 7-day culture supernatants. However, the increase of IgE above the levels measured in the initial cell pellets, which was found in most grass-sensitive subjects, clearly reflected newly synthesized IgE. Both cycloheximide and puromycin were capable of reducing significantly the IgE concentration in culture supernatants when it was greater than the amount found in the initial cell pellets. The treatment of cells with mitomycin C was also able to decrease significantly the amount of IgE released in the supernatant after day 3 of culture.