IgD: A Major Immunoglobulin on the Surface of Lymphocytes from Patients with Chronic Lymphatic Leukemia

Abstract

Abstract Previous studies on the characterization of surface immunoglobulins of lymphocytes from CLL2 patients indicated that the cell-associated immunoglobulin was monoclonal with respect to heavy and light chain class with IgM being by far the most common Ig class observed (1–4). Our earlier study of CLL involved analysis for the presence of IgG, IgA, and IgM. Some cases were observed in which neither heavy nor light chains were detectable and others in which only light chains could be detected (1). A more detailed investigation of one of these patients demonstrated IgD as the major Ig class associated with these cells. We have accordingly evaluated other unselected cases of CLL for the presence of IgD on the lymphocyte surface. The current report details these studies and the relationship of IgD to IgM on the surface of CLL lymphocytes. Methods. Lymphocytes were obtained from patients with CLL having white blood counts ranging from 20,000 to 200,000 cells/mm3. Lymphocytes were purified by dextran sedimentation followed by Ficoll-Hypaque centrifugation (1). The cells were washed three times in Hanks’ balanced salt solution for fluorescent studies and six times in the same buffer for quantitative studies. Quantitation of IgM and IgD was performed by using inhibition of a radioimmunoassay as previously described (5). Lactoperoxidase - catalyzed radioiodination of viable lymphocytes was also performed as previously described (6). Lysis of cells was performed with 0.5% Nonidet P40. Immunoprecipitation by a direct technique with carrier immunoglobulin and anti-immunoglobulin was followed by analysis on sodium dodecyl sulfate polyacrylamide gels. Direct immunofluorescence was performed as previously described (1). Specificity of the antisera were established by demonstrating a lack of inhibitory capacity of immunoglobulin classes other than the ones being assayed for (e.g., IgM, IgG, IgA, and IgE of kappa or lambda type did not inhibit the anti-IgD reagent). This specificity was established separately for each of the three test systems used.