Surface Ia-like expression and MLR-stimulating capacity of human leukemic myeloblasts: implications for immunotherapy and prognosis.

Surface Ia-positive cells were found to vary from 0 to 100% in initial blood specimens from 37 adults with acute myelogenous leukemia (AML). When myeloblasts from 19 patients were tested against panels of lymphocytes from 5 to 19 normal donors, mean stimulation indices ranged from 1 to 60. Some leukemic myeloblasts strongly stimulated most allogenic responder lymphocytes whereas others produced almost no stimulation. The addition of antibody against human Ia to 28 mixed leukocyte reaction (MLR) combinations resulted in significant inhibition (p less than 0.001) of 3H-thymidine incorporation. Testing of myeloblastic Ia may have clinical relevance because patients with greater than 50% Ia-positive myeloblasts had a significantly longer survival than patients with fewer Ia-positive myeloblasts (p less than 0.04).