Heterogeneity of Ia antigen expression by proliferating nonlymphocytic leukemia blast cells

Abstract

In vitro systems were used to detect Ia‐like antigens on proliferating normal myeloid and acute nonlymphocytic leukemia (ANLL) blast cells. Incubation of normal bone marrow cells with a monoclonal anti‐Ia antibody and complement resulted in toxicity for both granulocyte/macrophage progenitors (CFU‐GM) (toxicity 79%–100%) and cells proliferating in liquid culture in response to placenta‐conditioned medium colony‐stimulating factor (CSF) or medium conditioned by normal, phytohemagglutinin (PHA)‐stimulated mononuclear cells. In contrast, effects of anti‐Ia antibody and complement on blast colonyforming cells and 3H‐TdR incorporation in liquid culture from eight patients with ANLL were variable. Colony growth with CSF after treatment was 0% to 91% of control growth and did not correlate with display of Ia‐like antigens. Survival of ANLL cells growing in liquid cultures was even more variable after anti‐Ia+ complement treatment (28%–227% of control). The presence of Ia‐like antigens did not distinguish ANLL cells responding to PHA‐conditioned medium from those responding to CSF in either colony or liquid culture. Dose–response curves for ANLL cells in liquid culture were similar before and after treatment with anti‐Ia+ complement. In contrast to normal myeloid precursor cells, which show uniform display of Ia‐like antigens, display of Ia antigen by proliferating leukemia cells is highly variable from patient to patient. Anti‐Ia reagents such as this one would not be effective in treating ANLL marrow for autologous transplantation. Cancer 56: 1957‐1962, 1985. Copyright © 1985 American Cancer Society