Combined Effects of Differentiation-inducing Factor and Other Cytokines on Induction of Differentiation of Mouse Myeloid Leukemic Cells

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Abstract
Mouse myeloid leukemic M1 cells are induced to differentiate into macrophage-like cells by differentiation-inducing factors (D-factors) and granulocyte colony-stimulating factor. We examined the effects of recombinant human tumor necrosis factor (rTNF), lymphotoxin (rLT) and interleukin 1 (rIL-1) on the induction of differentiation of M1 cells, compared with the effects of D-factor purified from the conditioned medium of mouse Ehrlich ascites tumor cells and recombinant human granulocyte colony-stimulating factor (rG-CSF). rIL-1 induced phagocytic activity, a typical marker of cell differentiation, in at most 30% of M1 cells at concentrations ranging from 10-10 M to 10-7 M. The differentiation-inducing activity of rIL-1 was similar to that of rG-CSF and less than that of D-factor. rTNF induced phagocytic activity in 14% of M1 cells only at a high concentration (10-7 M). rLT did not induce differentiation of the cells even at 10-7 M. rTNF stimulated induction of differentiation of M1 cells by D-factor, rG-CSF or rIL-1 by two or three fold. The combination of any two of the cytokines D-factor, rG-CSF and rIL-1 induced differentiation of M1 cells more efficiently than any of these cytokines along. Moreover, the combination of three cytokines rG-CSF, rIL-1 and rTNF, all of which are known to be produced by macrophages, was more effective than the combination of any two of these cytokines in induction of differentiation of M1 cells.