Cell-mediated immune response to fractionated products of Actinomyces viscosus cultures

Since bacterial invasion of host tissue has not been shown to occur in the course of periodontitis, many investigators believe that products released from dental plaque microorganisms enter the tissue and elicit a series of host responses leading to the pathological condition. This study, therefore, was designed to explore the possibility that cell-free products isolated from Actinomyces viscosus cultures are able to induce cell-mediated immunological responses in experimental animals. Hartley strain guinea pigs were sensitized with concentrated cell-free products of A. viscosus culture supernatant fluids mixed with Freund complete adjuvant. After 10 to 17 days the animals responded to challenge with this material with skin reactions indicative of delayed-type hypersensitivity. Furthermore, cells isolated from sensitized animals produced mitogenic factor and macrophage migration inhibition factor (MIF) when cultured with the material. The cell-free culture products were fractionated by column chromatography and electrophoresis. Several partially purified components were shown to induce cell-mediated responses in guinea pigs as determined by skin tests and by mitogenic factor and MIF assays. It is apparent that this single microorganism associated with dental plaque is capable of producing several substances which can induce a cell-mediated immune response and subsequent tissue inflammation in laboratory animals.