Effects of IL-17 on Human Gingival Fibroblasts

Interleukin (IL)-17 is present in inflammatory periodontal lesions, thus suggesting a role in mediating inflammation. We tested the hypothesis that IL-17, especially when combined with interferon (IFN)-γ, may modulate the responses of human gingival fibroblasts (HGFs). IL-17 induced IL-8 and minimal intercellular adhesion molecule (ICAM)-1 expression. It had no effect on expression of HLA-DR, CD40, or the immune-suppressive enzyme indoleamine 2,3-dioxygenase (IDO). The effects of IL-17 on HGFs were compared with those of IFN-γ. Unlike IL-17, IFN-γ augmented the expression of HLA-DR, ICAM-1, and IDO, but not IL-8. Thus, IL-17 and IFN-γ induce different HGF responses when administered separately. Interestingly, when IL-17 and IFN-γ were combined, marked enhancement of ICAM-1, IL-8, and IDO expression by HGFs was observed. These findings suggest that IL-17, especially when combined with IFN-γ, could play an important role in immune modulation through stimulation of HGFs in periodontal disease.