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Three human gingival fibroblast cell lines were used to determine whether they could be induced by a synthetic RNA and superinduced by metabolic inhibitors to produce interferon (IFN-beta). When established procedures were followed for human fetal or newborn skin fibroblast cell lines, the adult gingival fibroblasts produced comparable amounts of IFN-beta. It was shown that the superinducers alone would not cause an IFN-beta production response, and that the absence of serum in the production medium also inhibited the production of IFN-beta. The effect of IFN-beta on cell growth was carried out in T-flasks seeded with 10(5) HEp-2 cells. After one and two wk, the cells of triplicate control flasks and triplicate flasks containing various dilutions of the production media were enumerated to determine a cell multiplication inhibition (CMI) value. A correlation between the IFN-beta content and the CMI effect, however, was not obtained, and it was concluded that other CMI agents, possibly more potent than the IFN-beta, were being produced by the stimulated human gingival fibroblasts. Cell protein assays which gave a high ng/cell protein content correlated with TEM micrographs which showed clusters of complex lysosomes, primarily in cells cultured in the IFN-beta-containing nutrient. However, since commercial IFN-beta initiated no such lysosomal response, it was further concluded that the complex lysosomes were due to CMI agent(s) other than IFN-beta.

Phatocytosis by a human gingival epithelial-like cell line in tissue culture was studied using latex beads as a marker. Electron microscopic and chemical analyses revealed that the cells ingested the beads in a quantitative and reproducible manner. This phagocytosis system is potentially useful for studying the effects of dental plaque on cell metabolism.