Mycoplasmal induction of cytokine production and major histocompatibility complex expression

The mycoplasmas are a diverse set of bacteria that, in the course of their interactions with cells of the immune system, have a wide range of immunomodulatory effects. These effects include polyclonal stimulation of proliferation of T and B lymphocytes; activation of cytolytic activity of macrophages, natural killer cells, and cytotoxic T cells; and stimulation of production of cytokines (interleukin [IL]-1, IL-2, IL-4, IL-6, interferon [IFN]-alpha, IFN-beta, IFN-gamma, tumor necrosis factor-alpha, and granulocyte-macrophage colony-stimulating factor [GM-CSF]) by immunocompetent cells. Mycoplasmas have also been shown to induce major histocompatibility complex (MHC) expression in macrophage cell lines and cultures. This report demonstrates that induction of MHC expression by mycoplasmas is directly due to increases in the transcriptional activity of MHC genes. Experiments attempting to determine if the mechanism responsible for these increases in MHC expression requires the production of cytokines have demonstrated that production of IFN-gamma, IL-4, and GM-CSF is probably not involved.