IL-17 and IFN-γ production in peripheral blood following BCG vaccination and Mycobacterium tuberculosis infection in human

BACKGROUND: During Mycobacterium tuberculosis (Mtb) infection, cells of the immune system rely on cytokines to regulate the activity of other immune and structural cells such as IFN-gamma and IL-4. Recent studies suggest that Th17 cells secreting IL-17 may play a potential role in tuberculosis (TB) development. AIM: To assess the effect of IL-17 on TB development, we provide a systematic review on the production of IL-17, IFN-gamma and IL-4 in infants or children vaccinated with BCG and in TB patients. MATERIALS AND METHODS: The literature relevant with IL-17 and IFN-gamma production with or without IL-4 on human TB was retrieved from PubMed, EMBASE, Cochrane Library, BIOSIS Previews and the China Biomedicine Literature Databases (CBM) using the search terms "Interleukin-17 or Th17 cells" and "Tuberculosis". The information of included studies, the production of IL-17 and IFN-gamma responding to antigens in the peripheral blood in vitro, was independently extracted by the first two researchers and subsequently qualitatively analyzed. RESULTS: Nine studies from a total of 226 retrieved publications met the criteria. These included studies showed that BCG vaccination induced dramatically high level of IL-17 similar to IFN-gamma; The level of IL-17 and IFN-gamma were low while IL-4 was high in patients with active TB; IL-17 and IFN-gamma had a similar trend of increase during the conversion from active to latent TB while IL-4 inclined to decrease in this process. CONCLUSIONS: IL-17 acts as an effector molecule similar to IFN-gamma after BCG vaccination and Mtb infection to protect human against TB. The current findings do not support IL-17 as an inducer of tissue damage in TB.