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Differentiation Capacity and Other Properties of the Leukemic Cells of Chronic Lymphocytic Leukemia *

It is well established that chronic lymphocytic leukemia (CLL) in man is a clonal proliferation of B cells. In the majority of cases, the leukemic lymphocytes bear IgM and IgD as their surface immunoglobulins(Ig)(Fuet al. 1974a, Kuboetal. 1974, Preud'homme et al. 1974). Despite a number of differences from normal B cells, these homogeneous B cell populations have been helpful in the studies of human B lymphocytes. In this laboratory they have facilitated the analysis of the orientation of surface IgM and IgD and the possible sites of membrane insertion of these molecules (Fu & Kunkel 1974). They also have helped in the demonstration and characterization of the presence of la-like molecules on human B lymphocytes (Winchester et al. 1975). Recently, a small group of CLL cases in which a monoclonal serum Ig protein is present in addition to marked lymphocytosis have proven of special interest. In some of these cases, a direct relationship between the leukemic lymphocytes and the serum monoclonal protein has been documented by idiotypic analysis involving the serum Ig band and the surface Ig on the leukemic cells (Fu et al. 1974b, Salsano et al. 1974, Hurley et al. 1978). The availability of the idiotypic determinant as a leukemic specific marker and a clone of B cells at different stages of maturation, spanning from lymphocytes to plasma cells, has proven very useful. In this review primary emphasis will be placed on studies involving the differentiation of leukemic B cells to plasma cells. Analyses of these leukemic cells have provided considerable information directly applicable to normal B cells. In addition, certain functional and structural abnormalities of these leukemic B cells will also be discussed.