Background. Mycoplasma hominis, a human urogenital pathogen, is involved in genital and extragenital infections and arthritis, particularly in immunocompromised patients. The interleukin (IL) 23/T helper (Th) 17 axis is associated with inflammatory and autoimmune diseases. The aim of this study was to assess the IL-23 response to M. hominis in human dendritic cells (DCs) and the CD4+ T-cell differentiation in response to M. hominis–infected DCs.
Methods. Human monocyte–derived DCs were cultured with phosphate-buffered saline, lipopolysaccharide, or M. hominis PG21. Cocultures with heterologous T cells were performed. Extracts from M. hominis were separated and incubated with DCs. Isolates from different clinical syndromes were tested.
Results. M. hominis induced the maturation of human DCs with predominant IL-23 secretion in a Toll-like receptor 2–dependent manner. The in vitro immunomodulatory capacity of M. hominis was contained in a lipoprotein-enriched fraction from the mycoplasma. M. hominis–activated DCs induced IL-17–producing CD4+ T cells. Interestingly, clinical isolates differed in their ability to promote IL-23 secretion by DCs.
Conclusions. Taken together, our findings demonstrate a major role for the IL-23/Th17 axis in the defense against M. hominis and indicate a potential role for these bacteria in inflammatory and autoimmune diseases.