ABSENCE OF THYMUS-DERIVED LYMPHOCYTE MARKERS IN MYELOGENOUS LEUKEMIA (PH1+) CELL LINE K-562

Abstract

The myelogenous leukemia cell line K-562 with a Ph1+ [Philadelphia] chromosome, derived from a patient with chronic myelogenous leukemia in terminal blastic crisis, is not a bone marrow derived lymphoblastic cell line, because the cells neither produce immunoglobulins nor possess complement receptors. Since it was suspected that blasts found in some patients with chronic myelogenous leukemia in blastic crisis might be thymus derived cells. Several parameters were studied to demonstrate that K-562 cells are not thymus derived lymphoblasts. The results of this study show no cross reactivity of antisera to K-562 cells with normal human thymocytes, lack of cytotoxicity of a specific horse antihuman thymocyte globulin for K-562 cells, failure of the treatment of K-562 cells with bovine thymosin to induce antigenic determinants and erythrocyte rosette receptors on K-562 cells, presence of receptors for the Fc portion of immunoglobulin G, absence of terminal deoxynucleotidyl transferase, and cytotoxicity of monkey antiserum to K-562 cells for malignant thymus derived cells (Molt-4). Absorption with Molt-4 cells abolished the cross reactivity with Molt-4 cells, whereas 60% of the antibody to K-562 cells remained in the immune serum. Studies of DNA polymerase activities revealed that K-562 cells have levels of polymerase .alpha. and .beta., like other proliferating cells, and an RNA dependent DNA polymerase activity, presumably representing polymerase .gamma.