Fc-receptors for IgE on human lymphocytes. Detection with a rosetting assay using a recombinant human/mouse IgE antibody and characterization with monoclonal antibodies.

Two monoclonal antibodies, M-L25 and M-L47, were produced against the human lymphoid Fc receptor for IgE (Fc epsilon R). These antibodies were identified by their ability to selectively inhibit the binding of IgE to Fc epsilon R+ lymphoid cells as demonstrated by a newly developed IgE rosetting assay. In this method, NIP coated ox erythrocytes were complexed with a NP-specific recombinant chimeric human/mouse IgE antibody and employed as indicator cells for the detection of Fc epsilon R+ cells. The anti-Fc epsilon R antibodies stained 4.6 +/- 2.3% of normal peripheral blood mononuclear cells, 0.4 +/- 0.3% of T cells, 22.2 +/- 11.7% of the non-T cell fraction, and 34.9 +/- 2.9% of tonsil cells. Less than 0.1% of monocytes, basophilic and eosinophilic granulocytes, platelets, and thymus cells were labelled. This indicates an antigenic heterogeneity of the low affinity Fc epsilon R on lymphocytes and the Fc epsilon R found on monocytes, platelets, and eosinophilic granulocytes. The lymphoid Fc epsilon R was immunoprecipitated by M-L25 from the lysate of surface iodinated lymphoid cells. Three polypeptide chains were identified having an apparent MW of 40, 82, and 100 kd under non-reducing, and of 42, 115, and 145 kd under reducing conditions, suggesting a multichain structure of the human lymphoid Fc epsilon R.