INVOLVEMENT OF NATURAL-KILLER-CELLS IN NITRIC-OXIDE PRODUCTION BY SPLEEN-CELLS AFTER STIMULATION WITH MYCOBACTERIUM-BOVIS BCG - STUDY OF THE MECHANISM OF THE DIFFERENT ABILITIES OF VIABLE AND KILLED BCG

Viable and killed BCC were compared for the ability to induce nitric o xide (NO) production in normal spleen cells and peritoneal exudate mac rophages, Stimulation of spleen cells with viable BCG resulted in a st rong expression of inducible NO synthase followed by an enhanced produ ction of nitrite. However, those responses were not induced after stim ulation with killed ECC or when macrophages were stimulated with kille d and viable BCG, The same level of TNF-alpha mRNA expression was obse rved in reverse transcription-PCR after stimulation of spleen cells wi th viable and killed BCC, However, IFN-gamma production was induced on ly when spleen cells were stimulated with viable BCG, Concurrent stimu lation of rIFN-gamma with either viable or killed BCG resulted in a st rong nitrite production by macrophages, Neutralization of IFN-gamma an d TNF-alpha caused a complete inhibition of nitrite production, Furthe rmore, anti-asialo GM1 Ab plus complement treatment abolished IFN-gamm a production after stimulation with viable BCG, indicating that the NK cell was the major source of IFN-gamma, and its production was trigge red only by stimulation with viable BCC, The present study showed that the ability of viable BCG to induce NO production is superior to that of killed BCG, and both IFN-gamma and TNF-alpha are essential for BCG -induced NO production by spleen cells, NK cells appeared to be import ant as a source of IFN-gamma, and the insufficient NO induction by kil led BCC was due to the inability to induce IFN-gamma from NK cells.