HETEROGENOUS NITRITE PRODUCTION BY IL-4-STIMULATED HUMAN MONOCYTES AND PERIPHERAL-BLOOD MONONUCLEAR-CELLS

The capacity of human peripheral blood mononuclear cells and monocytes to generate nitrites, spontaneously or in response to Interleukin-4 w as evaluated in vitro. Peripheral blood mononuclear cells and monocyte s were found to release significant amounts of nitrites after 8 to 12 days in culture. This spontaneous production of nitrites was inhibited in the presence of 1 mM N-G monomethyl-L-arginine, suggesting that th is process was dependent upon the L-arginine metabolism. The present d ata also indicated that addition of Interleukin-4 generally resulted i n an increased nitrite production, that was potentiated by IFN-gamma, inactive alone. The response of human monocytes to Interleukin-4 was m ore heterogenous than that observed with unfractionated peripheral blo od mononuclear cells. These results suggest that cell/cell interaction s could play an important role in the activation of the nitric oxide s ynthase pathway in human.