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).

The role of monocytes in phagocytosis and mixed leukocyte reactivity in human acute myeloid leukemia.

Lymphocyte proliferation, as measured by incorporation of tritiated thymidine (3H-TdR), was significantly enhanced (p less than 0.01) when macrophages sensitized by target myeloblasts were added to monocyte-depleted lymphocyte fractions in the mixed leukocyte reaction (MLR) with human leukemic myeloblasts as stimulators and panels of normal lymphocytes as responders. Monocyte addition in the same concentration range to unfractionated lymphocytes resulted in highly significant facilitation (p less than 0.0001) of MLR response patterns to myeloblastic stimulation. However, with substitution of a different myeloblastic stimulator, this facilitation was not observed. At higher monocyte-lymphocyte ratios (1:15) the monocytes appeared to be capable of strongly inhibiting the MLR. Monocyte capacity to engulf and kill Candida albicans organisms was normal in acute myeloid leukemia (AML) patients given "immunotherapy" with BCG and leukemic cells.