Endothelial cell receptors on leukemic plasma cells

The binding of peripheral blood mononuclear cells of 7 patients with plasma cell leukemia to rat lymph node high endothelial venules has been studied in vitro. The mononuclear cells adhered selectively to the high endothelial venules. Their neoplastic origin was proved by in situ demonstration of their monoclonal cytoplasmic immunoglobulins. The in vitro binding of bone marrow mononuclear cells of 4 patients with multiple myeloma to high endothelial venules was also studied. In two patients there was no high endothelial cell binding. In the two others some adhering cells were observed. The plasmacytoid nature of these cells was, however, excluded for lack of cytoplasmic immunoglobulins. Since cells at the end stage of B-cell differentiation lose their surface receptors associated with lymphocyte recirculation, the presence of endothelium-recognizing structures on leukemic plasma cells seems to be remarkable.