Erythrocyte-rosette receptor expression by chronic lymphocytic leukemia B lymphocytes

Erythrocyte (E) rosette-forming cells have been investigated in three patients with B chronic lymphocytic leukemia whose leukemic lymphocytes were easily identifiable. A small percentage of fresh neoplastic cells formed E rosettes in two patients. In every patient, most unstimulated, cultured leukemic lymphocytes became E⁺ and this was further enhanced by phytohemagglutinin and pokeweed mitogen stimulation or neuraminidase treatment. These E⁺ B cells lacked detectable T cell antigens (except for a weak expression of an antigen associated with the helper T cell subpopulation in one case). They were unreactive or weakly reactive by immunofluorescence with a monoclonal antibody to the E receptor. However, this antibody completely inhibited E-rosette formation. The enhanced expression of E-rosette receptors by in vitro cultured cells appeared to be dependent upon the presence of a small number of E-rosetting cells at the beginning of the culture. E-rosette receptor expression by leukemic lymphocytes was most likely in a fourth case (out of 9 patients studied). This finding may account for some of the discrepancies in the study of so-called T cells in B chronic lymphocytic leukemia.