Detection and characterization of monoclonal antibodies specific to IgE receptors on human lymphocytes by flow cytometry.

BALB/c mice were immunized with human lymphoblastoid cells (RPMI 8866 cells) expressing surface receptors for IgE (Fc epsilon R). Spleen cells from animals displaying high titres of anti-Fc epsilon R antibodies were fused with HGPRT-deficient NSI myeloma cells. Anti-Fc epsilon R antibodies were identified by a flow cytometric assay based on their ability to block the binding of IgE-coated fluorescent latex particles to Fc epsilon R-positive cells. Fourteen monoclonal hybridoma cell lines secreting antibody of the required specificity were amplified in tissue culture and then grown in the peritoneal cavity of BALB/c mice in order to obtain ascitic fluids with high antibody titres. The specificity of each monoclonal antibody (Mab) to lymphocyte Fc epsilon R was shown by the following observations: (i) the intact monoclonal antibody molecule or, in some cases, its F(ab')2 fragments blocked the binding of IgE to several Fc epsilon R(+) cell lines different from that employed for the initial immunization; (ii) the Mab bound directly to all the Fc epsilon R(+) cell lines tested, but not to several Fc epsilon R(-) cells as determined by indirect immunofluorescence; (iii) the binding of Mab to Fc epsilon R(+) cells was selectively blocked by IgE, but not by the other classes of Ig; and (iv) Mab had no effect on the binding of IgG to Fc gamma R on normal human peripheral blood mononuclear cells (PBMC).