Induction of interleukin-1 and -6 in human gingival fibroblast cultures stimulated with Bacteroides lipopolysaccharides

Abstract

Normal human gingival fibroblasts stimulated in vitro by lipopolysaccharides (LPS) from oral Bacteroides species produced cell-free and cell-associated thymocyte-activating factors (TAF). Neutralization assays using antisera to human interleukin-1α (HuIL-1α), HuIL-1β, and HuIL-6 revealed that cell-free TAF was attributable mainly to IL-1 β and that IL-6 augmented the TAF activity of IL-1 β in the culture supernatant. Another factor(s), however, may also be involved in cell-free TAF. By contrast, the active entity of cell-associated TAF was ascribed to IL-1α alone. Furthermore, IL-6 was detected mainly in the supernatant of fibroblast cultures stimulated with Bacteroides LPS. Fibroblasts pretreated with natural human beta or gamma interferon, but not those pretreated with alpha interferon, synthesized higher levels of cell-associated IL-1α in response to stimulation by Bacteroides LPS; however, no interferons exhibited direct IL-1-inducing activity or synergistic IL-1-inducing activity with LPS. Endogenously induced beta interferon was suggested to be necessary for fibroblasts to produce cell-associated IL-1α in response to Bacteroides LPS.