Epstein-Barr virus-induced gene 3 negatively regulates IL-17, IL-22 and RORγt

Epstein-Barr virus-induced gene 3 (EBI3) associates with p28 to form IL-27 and with IL-12p35 to form IL-35. IL-27Rα^-/- mice studies indicate that IL-27 negatively regulates Th17 cell differentiation. However, no EBI3, p28 or p35-deficiency studies that directly address the role of EBI3, p28 or p35 on Th17 cells have been done. Here, we demonstrate that spleen cells derived from EBI3^-/- mice produce significantly higher levels of IL-17 as well as IL-22 upon stimulation with OVA. In vitro derived EBI3^-/- Th17 cells also produced significantly higher levels of IL-17 and IL-22 than WT cells. The frequency of IL-17-producing cells was also elevated when EBI3^-/- cells were cultured under Th17 conditions. In addition, spleen cells from EBI3^-/- mice immunized with Listeria monocytogenes produced significantly elevated levels of IL-17 and IL-22. Furthermore, the Th17 transcription factor RORγt was significantly enhanced in EBI3^-/- cells. Finally, EBI3^-/- mice exhibited a reduced bacterial load following an acute challenge with L. monocytogenes or a re-challenge of previously immunized mice, suggesting that EBI3 negatively regulates both innate and adaptive immunity. Taken together, these data provide direct evidence that EBI3 negatively regulates the expression of IL-17, IL-22 and RORγt as well as protective immunity against L. monocytogenes.