Granulocyte-macrophage colony stimulating factor modulates the production of TNF alpha by differentiated U937 cells infected with Leishmania major

In this work, the production of tumor necrosis factor alpha (TNF alpha) dur ing interaction of human phagocytes with the intracellular parasite Leishma nia major was further investigated. The human monocytic cell line U937, dif ferentiated with a combination of 1 alpha, 25 dihydroxyvitamin D-3 (VD) and retinoic acid (RA), or with granulocyte macrophage colony stimulating fact or (GM-CSF) was used. Differentiated U937 cells were infected with Leishman ia major promastigotes, and TNF alpha was assayed in cell culture supernata nts. It was found that the cytokine was produced only by U937 cells differe ntiated with VD/RA and further incubated with GM-CSF and LPS or interferon gamma (IFN gamma). L. major induced TNF alpha production only in the presen ce of GM-CSF. No direct relationship was found, however, between production of TNF alpha and resistance of differentiated U937 cells to infection with L. major.