[Thymocyte activating factors in human gingival fibroblast cultures stimulated by oral Bacteroides lipopolysaccharides: induction, identification and modification by various cytokines]

Abstract

Normal human gingival fibroblasts stimulated in vitro by lipopolysaccharide (LPS) from black pigmented oral Bacteroides species produced cell-free (CF) and cell-associated (CA) thymocyte activating factors (TAF). The LPS from other bacteria, including Escherichia coli and Salmonella species, induced minimum levels of TAF in the cultures. The CF-TAF was partially inhibited by anti-human interleukin (HuIL)-1 beta or HuIL-6 antibody, but not by anti-HuIL-1 alpha antibody. However, complete inhibition of the CF-TAF was not observed upon addition of both anti-HuIL-1 beta and HuIL-6 antibodies. Fibroblasts stimulated with Bacteroides LPS released high levels of CF-IL-6 activity. Recombinant (r) HuIL-6 negligibly exhibited TAF activity even in high doses up to 500 U/ml, although it augmented the TAF activity of rHuIL-1 beta. These findings indicated that the CF-TAF consisted mainly of IL-1 beta, and that IL-6 enhanced TAF activity of IL-1 beta. However, other TAF factor (s) may be present in CF specimens. In contrast to CF-TAF, the CA-TAF was inhibited with anti-HuIL-1 alpha. Recombinant human tumor necrosis factor (rHuTNF) directly stimulated fibroblasts to produce CA-TAF, and it also primed them to enhance CA-TAF induction in response to Bacteroides LPS. On the other hand, natural human interferons (nHuIFN) alpha, beta, and gamma did not induce CF- or CA-TAF in fibroblasts. When fibroblasts were primed with nHuIFN beta or gamma, the CA-TAF production by the cells in response to LPS, but not rHuTNF, was markedly enhanced.(ABSTRACT TRUNCATED AT 250 WORDS)