PORPHYROMONAS-GINGIVALIS LIPOPOLYSACCHARIDE STIMULATION OF HUMAN MONOCYTES - DEPENDENCE ON SERUM AND CD14-RECEPTOR

The purpose of this study was to investigate factors influencing the ability of lipopolysaccharide (LPS) derived from Porphyromonas gingivalis to elicit secretion of tumor necrosis factor-alpha (TNFalpha) from human monocytes (adherent mononuclear cells). The results indicate that P gingivalis LPS stimulation of TNFalpha from monocytes is comparable to LPS from Escherichia coli. Both LPS, although structurally different, increased TNFalpha secretion in a dose-dependent manner. In serum-free conditions, TNFalpha secretion was relatively low, but it dramatically increased at human serum concentrations as low as 1%. Maximal secretion was observed in the presence of 10% serum, with a slight decrease at higher serum concentrations. The CD14 molecule is a putative monocyte LPS receptor. When cells were pre-incubated with a blocking monoclonal antibody (My4) to CD14, TNFalpha-mRNA accumulation and TNFalpha secretion were reduced to control levels at LPS concentrations of up to 10 ng/ml. At higher LPS concentrations, the blocking effect was only partial, in spite of 50-fold excess antibody concentration. The blocking effect was observed only in the presence of serum. The effect of the CD14 antibody was dose-dependent with saturation at 2.5 mug/ml. The results suggest that CD14 is one of the major receptors for P gingivalis LPS but highlight the necessity to investigate other cell-surface receptors mediating P gingivalis-LPS interactions. These interactions are believed to be important in the pathogenesis of periodontal destruction.