An interferon-γ-producing Th1 subset is the major source of IL-17 in experimental autoimmune encephalitis

ThIL-17 (IL-17+/IFN-γ−) cell lines are significantly more encephalitogenic than Th1 (IL-17−/IFN-γ+) cell lines in adoptive transfer EAE models. In actively induced EAE short ex vivo peptide stimulation identifies an IL-17+/IFN-γ+ population of CD4+ CNS-infiltrating MOG35–55-specific T cells, which outnumber IL-17+/IFN-γ− cells by approximately 3:1 as disease develops. A decrease in numbers of IL-17+/IFN-γ+ cells following in vitro culture is accompanied by an increase in IL-17−/IFN-γ+ cell numbers. Together these ex vivo and in vitro observations imply that the Th1 lineage is more encephalitogenic than is suggested by adoptive transfer of Th1 (IL-17−/IFN-γ+) cell lines which have been terminally differentiated in vitro.