Leukemia-associated antigens detected by a nonhuman primate antiserum to a Ph1+ myeologenous leukemia cell line

The specificity of an antiserum (titer 1:500) raised in a monkey against K-562 undifferentiated cells with the Philadelphia chromosome (Ph 1 ) was determined. Antibody-dependent, complement-mediated cytotoxicity was demonstrated for both bone marrow cells and peripheral leukocytes from patients with myelogenous and lymphatic leukemias, but not for mature normal hematopoietic cells and those from patients with leukemia in remission. A monospecific antiserum for K-562 cells and peripheral leukocytes from three patients with chronic myelogenous leukemia (CML) was obtained after multiple absorptions with peripheral leukocytes from patients with acute and chronic lymphatic leukemias as well as acute myelogenous leukemia. The minimal number of Ph 1 + myelogeneous leukemia cells needed to remove the antibody completely from 1 ml of the immune serum was found to be 12 × 107 K-562 cells versus 25 × 107 peripheral leukocytes (52% immature and 48% mature) in different stages of maturation from a patient with CML. Other results indicated that progenitors of normal and undifferentiated malignant cells of hematopoietic origin might share some common antigenic determinants that reacted with this antiserum but that could be removed by appropriate absorptions.