Lipopolysaccharides (LPS) of oral black-pigmented bacteria induce tumor necrosis factor production by LPS-refractory C3H/HeJ macrophages in a way different from that of Salmonella LPS.

Some lipopolysaccharide (LPS) preparations from S- or R-form members of the family Enterobacteriaceae and oral black-pigmented bacteria (Porphyromonas gingivalis and Prevotella intermedia) are known to activate LPS-refractory C3H/HeJ macrophages. When contaminating proteins are removed from R-form LPS of Enterobacteriaceae by repurification, however, this ability is lost. In the present study, we investigated the capacity of LPS from P. gingivalis, P. intermedia, Salmonella minnesota, and Salmonella abortusequi to induce production of tumor necrosis factor (TNF) in gamma interferon-primed C3H/HeJ macrophages before and after repurification. P. abortusequi S-LPS was fractionated by centrifugal partition chromatography into two LPS forms: SL-LPS, having homologous long O-polysaccharide chains, and SS-LPS having short oligosaccharide chains. Prior to repurification, all LPS forms except SL-LPS induced TNF production in both C3H/HeJ and C3H/HeN macrophages. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that repurification removed contaminating protein from the preparations, and repurified SS-LPS and S. minnesota Ra-LPS no longer stimulated TNF production in C3H/HeJ macrophages, although C3H/HeN macrophages remained responsive. In contrast, repurified oral bacterial LPS retained the capacity to induce TNF production in C3H/HeJ macrophages. Oral bacterial LPS preparations also were not antagonized by excess inactive, repurified SL-LPS; Ra-LPS; Rhodobacter sphaeroides lipid A, a competitive LPS antagonist, or paclitaxel, an LPS agonist, and they were comparatively resistant to polymyxin B treatment. Nevertheless, oral bacterial LPS was less toxic to D-galactosamine-treated C3H/HeN mice than was LPS from Salmonella. These findings indicate that the active molecule(s) and mode of action of LPS from P. gingivalis and P. intermedia are quite different from those of LPS from Salmonella.