Idiotypic Uniformity of Cell Surface Immunoglobulin in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is thought to be a malignancy of bone marrow-derived (B) lymphocytes, since the leukemic cells from a majority of patients bear easily detectable membrane-bound immunoglobulin (Ig) (1), possess a complement (C3) receptor (2), and do not bind sheep erythrocytes (3). Since in most studies (1, 3-5), but not all (6), the cells from an individual patient bear Ig restricted to a single light chain class, it is suspected that the CLL lymphocytes represent the progeny of a single clone of B cells. The present study provides support for the clonal proliferation of CLL cells by demonstrating in a single patient that the Ig on virtually all of the CLL cells possess the same idiotypic (variable region) determinants. The anti-idiotypic serum, prepared against a circulating paraprotein, reacted only with the paraprotein and the surface Ig on the CLL cells and not with a variety of other serum or cell-bound Igs.