The monoclonal nature of lymphatic leukemia.

Monoclonal membrane-bound Ig were found by immunofluorescence on the lymphocytes in the vast majority of cases of chronic lymphocytic leukemia. The distribution of H and L chains among these patients reflected the distribution of surface Ig on normal lymphocytes and IgM was the predominant class. The importance of the study of surface Ig synthesized in vitro is outlined. The simple staining of freshly drawn cells may lead to erroneous conclusions, since an apparently polyclonal staining can result from the anti-IgG antibody activity of a monoclonal surface IgM, from the attachment of immune complexes at the lymphocyte surface or from the binding of serum antibodies to cell membrane determinants. A biclonal proliferation, characterized by distinct surface-Ig markers, was demonstrated in several cases of chronic lymphatic leukemia. Monoclonal surface Ig were also detected on the lymphoblasts in 2 cases of acute transformation of chronic lymphocytic leukemia, in several patients with acute lymphosarcoma cell leukemia and in 1 case of acute lymphatic leukemia. In most cases of acute lymphatic leukemia, the leukemic cells were devoid of detectable B- or T-cell membrane markers. In 2 cases of acute lymphatic leukemia, 1 case of chronic lymphatic leukemia and in all patients with the Sezary syndrome, the leukemic cells appeared to be thymus-derived.