Long-lasting polymorphonuclear leukocyte oxidative burst activation by products of lipopolysaccharide-treated mononuclear cells is only partially due to tumor necrosis factor.

Abstract

Supernatants of human mononuclear cells cultured in the presence of LPS (LPS-MNC-SN) directly induced production of superoxide by isolated polymorphonuclear leukocytes, measured as superoxide dismutase--inhibitable cytochrome c reduction or, more sensitively, Lucigenin-enhanced chemiluminescence. Of recombinant human cytokines, only TNF and to a lesser degree also LT, but not GM-CSF, showed this activity. Neutralising antibody to TNF reduced the activity of LPS-MNC-SN to activate an oxidative burst in polymorphonuclear leukocytes by 30-50%. In contrast, killing of TNF-sensitive mouse L 929 cells by LPS-MNC-SN was completely inhibited by anti-TNF, while the L929 killing assay was at least as sensitive for TNF as the granulocyte chemiluminescence assay. Material with granulocyte chemiluminescence inducing (GCI) activity but devoid of TNF was obtained by sequential chromatography of LPS-MNC-SN on Mono Q anion exchange and phenyl sepharose hydrophobic interaction chromatography. The time course of GCI-induced superoxide generation was prolonged with a tmax of approximately 60 minutes. Subsequent separation of this GCI-active material on Superose gel filtration yielded two overlapping activity peaks with apparent molecular weights of approximately 40-50 and 200 kDa. Further, two distinct GCI activity peaks were found when Mono Q--and phenyl-sepharose--separated material was subjected to reversed phase chromatography. Thus, in addition to TNF, LPS-triggered mononuclear cells produce also other granulocyte chemiluminescence inducing mediators which appear distinct from presently known cytokines.