Contamination with Mycoplasma spp. induces interleukin-13 expression by human skin fibroblasts in culture

The mycoplasmas comprise a discrete group of microorganisms that are known to exert a range of effects upon cells derived from the immune system. Some of these interactions turn out to be immunomodulatory, such as polyclonal stimulation of T and B cells or enhancement of the cytolytic potential of macrophages, NK cells and T lymphocytes. Immunologically committed cells, when infected with mycoplasmas, can also increase the production of cytokines (IL-1, IL-2, IL-4 and IL-6), interferon (IFN) gamma, tumor necrosis factor-alpha (TNF-alpha) and colony-stimulating factors (particularly GM-CSF). Moreover, mycoplasmas are potent inductors of cytokine secretion by fibroblasts in culture. Since growth factors are determinants for the activation and proliferation of immunocompetent cells in vitro, we decided to investigate if these effects are concordant with the finding of mycoplasma contamination. In order to address this question, we compared the pattern of lymphokine secretion by normal-derived human fibroblasts in culture with and without Mycoplasma spp. contamination. We found those human fibroblasts that have been contaminated with mycoplasma show production of IL-13 at the transcriptional level. This effect coincides with discrete morphological changes as compared to uncontaminated human fibroblasts. This is the first report to acknowledge that mycoplasma contamination can induce mRNA expression for IL-13 in cultured human fibroblasts.