Stimulation of human lymphocytes in vitro by leucocytes from patients with untreated acute myeloid leukaemia.

Leucocytes from sixteen untreated acute myeloid leukaemia (AML) patients were tested for their ability to stimulate lymphocytes from each of twelve normal donors. Of 192 tests between the stimulating AML leucocytes, and responding lymphocytes, 42% resulted in positive lymphocyte stimulation, in contrast to one-way mixed lymphocyte culture (MLC) responses, involving the same lymphocyte donors, which were 100% positive. Lack of stimulation by AML leucocytes was significantly associated, in 11% of the tests, with two or more HLA-A and/or -B antigens common to the responding lymphocyte and stimulating AML leucocyte. The most stimulatory of the AML leucocytes were obtained from two high-leucocyte-count acute myelomonocytic leukaemia patients. The stimulatory capacity of AML leucocytes did not correlate with the clinical fate of the cell donor. Presence of contaminating lymphocytes from the patient in the AML leucocyte samples did not account for the differences in stimulatory capacity between AML leucocytes. Limited in vitro viability of AML leucocytes was ruled out as a factor causing poor lymphocyte stimulation. Kinetic studies showed that AML leucocytes induce either an MLC-type response, or no response at all. Differences in response kinetics were observed between two normal and two remission AML patients, the latter receiving active immunotherapy. Pronase treatment of AML leucocytes failed to increase their stimulatory capacity, but distilled H2O markedly reduced it. The significance of the results is discussed in relation to lymphocyte stimulation by other types of allogeneic cell, and in the context of active immunotherapy of AML.