Human IgE synthesis in vitro. Detection with monoclonal antibodies

Using monoclonal anti-human IgE antibodies recognizing the D epsilon 1 or D epsilon 2 epitope, we have developed a sandwich radioimmunoassay (RIA) to determine IgE in human cell cultures. With the help of this assay, various methods of measuring an actual de novo IgE synthesis were compared. It was necessary to subtract performed IgE from released IgE in the culture supernatant and the IgE associated to the cultured cells, in order to determine a net IgE synthesis which would reflect de novo synthesized IgE. Using this differential in vitro IgE assessment, no net IgE synthesis could be demonstrated in culture conditions which lead to strong IgG synthesis. Actual net in vitro IgE antibody production was only found in approximately 30% of cell cultures from atopic donors. This spontaneous IgE synthesis did not correlate to the serum IgE levels of the patients. However, correlations were found between serum IgE levels and amount of performed, released or cell-associated IgE of the cultures.