The serological detection of leukemia‐associated antigens in chronic leukemia: Correlation with disease status

Changes in the expression of leukemia‐associated antigens (LAA) on the peripheral blood cells of patients with chronic lymphocytic leukemia (CLL) and chronic myelogenous leukemia (CML) were monitored over a period of several months with a battery of heterologous antisera in a complement‐dependent microcytotoxicity test system. The sera were prepared by immunization of rabbits and monkeys with human CLL, CML, or acute lymphoblastic, myeloblastic, or myelomonocytic leukemic cells, or cell extracts. Following extensive adsorption with normal human erythrocytes and leukocytes, these sera did not exhibit reactivity with peripheral blood monuclear cells, nor, in most cases, with enriched B‐lymphocyte preparations from healthy donors. Cells from CLL patients reacted mainly with adsorbed antisera raised against lymphocytic leukemic cells, but there was significant cross‐reactivity with antisera raised against myelomonocytic leukemia cells; the number and intensity of positive reactions correlated with leukemic cell counts. Cells from patients in the chronic stage of CML reacted almost exclusively with adsorbed antisera to myeloid leukemic cells. However, blastic transformation of CML was regularly accompanied and on one occasion preceded by the appearance of reactivity with antisera to lymphocytic leukemic cells. During remission, peripheral blood cells from most CML patients were LAA‐negative; positive serologic reactions were often followed by major hematologic and clinical deterioration within a few months. These observations suggest that serological monitoring of LAA may represent a useful adjunct to present methods of evaluating the course and prognosis of chronic leukemias. Serological reactions may also have some utility in the differential diagnosis of leukemia.