Modulatory effect of Dalton's lymphoma cells on the production of reactive nitrogen intermediates, interleukin-1 and tumor necrosis factor by murine peritoneal macrophages

The effect of Dalton's lymphoma (DL) cells on the production of reactive nitrogen intermediates (RNI), interleukin-1 (IL-1) and tumor necrosis factor (TNF) by murine peritoneal meso-phages was investigated. Treatment of macrophages with LPS resulted in significant enhancement in the production of RNI, soluble and membrane-associated IL-1 and TNF. A significant inhibition in the production of RNI and IL-1 was observed when the macrophages were co-incubated with DL cells whereas TNF production was enhanced. Incubation of macrophages in the presence of DL cells alone even in the absence of LPS could induce production of TNF level comparable to that of LPS-treated macrophages. Paraformaldehyde-fixed DL cells and DL cell conditioned medium could also inhibit RNI production by macrophages. On the other hand pre-exposure of macrophages to viable DL cells or DL cell-conditioned medium prior to treatment with LPS could prime the macrophages for enhanced production of RNI. This study indicates that the regulatory effect of lymphoma cells on macrophage activation may have relevance of the host defence against tumors. (author)