Fc-Receptors for IgE on Human Lymphocytes. Detection with a Rosetting Assay Using a Recombinant Human/Mouse IgE Antibody and Characterization with Monoclonal Antibodies

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Abstract
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 oxa of erythroycytes 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 the 0.1% of monocytes, basophilic and eosiniphilic granuloctyes, platelets, and thymus cells were 1a-belled. This indicates an antigenic heterogeneity of the low affinity Fc.epsilon.R on lymphocytes and the Fc.epsilon.R found on macrocytes, 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 kg under reducing conditions, suggesting a multichain structure of the human lymphoid Fc.epsilon.R.