Inductive effect of Porphyromonas gingivalis fimbriae on differentiation of human monocytic tumor cell line U937

This study used the human monocytic tumor cell line U937 to examine whether Porphyromonas gingivalis fimbriae induce differentiation of monocyte/macrophage progenitors. When the progenitor cells were incubated with P. gingivalis fimbriaè, the incubation resulted in increased Fc rosette formation and increased CD11b production by the cells. The presence of a protein kinase C inhibitor, H7 or calphostin C, in the medium eliminated the stimulatory effects of P. gingivalis fimbriae on Fc rosette formation. Furthermore. CD11b expression was inhibited by calphostin C. In contrast, HA1004, an inhibitor of cyclic nucleotide-dependent protein kinase. had no effect on P. gingivalis fimbriae-induced Fc rosette formation or CD11b expression. These results demonstrate that P. gingivalis fimbriae are a potent inducer of the differentiation of the monocyte/macrophage tumor cell line U937, most probably via cyclic nucleotide-independent protein kinase C.