In vitro synthesis of IgE by human lymphocytes. III. IgE-potentiating activity of culture supernatants from Epstein-Barr virus (EBV) transformed B cells.

Seven Epstein--Barr virus (EBV)-transformed B cell lines were derived from circulating lymphocytes of two atopic and two non-atopic individuals, two preparations of cord blood lymphocytes and one tonsillar lymphocyte preparation. All the cell lines contained a significant proportion of cells expressing Fc epsilon R as detected by rosette formation with IgE-coated bovine erythrocytes (E-IgE) and by flow cytometry using IgE-linked to fluorescent microspheres. None of the cell lines displayed FcR for IgA, IgM or IgG. The cell-free supernatants (CFS) of EBV-transformed cells contained IgE-binding factors (IgE-BFs) detected by their ability to inhibit the binding to RPMI 8866 cells of either E-IgE or IgE-linked to microspheres. Whereas these CFS enhanced the synthesis of IgE and suppressed the synthesis of IgG by purified B lymphocytes isolated from the blood of allergic donors and cultured in the absence of stimulant, their effect on the synthesis of IgA or IgM was not predictable. CFS significantly enhanced the secretion of IgE by the U266 myeloma cell line without interfering with secretion of IgM, IgG or IgA by EBV-transformed cells. These data are in accord with similar properties of RPMI 8866 cells and suggest that B lymphocytes might play a regulating role in the IgE synthesis.