Interleukin-17 plays a role in exacerbation of inflammation within chronic periapical lesions

Interleukin (IL)-17 plays an important role in inflammation and certain autoimmune diseases. However, its role in the pathogenesis of chronic dental periapical lesions has not been studied. Periapical lesion mononuclear cells (PL-MNC) were isolated from inflammatory cells and phenotypically analyzed by immunocytochemistry. The cells were cultured in vitro and IL-17 and IL-8 were measured in the culture supernatants. Controls were peripheral blood (PB) MNC. The level of IL-17 and the proportion of neutrophils were significantly higher in symptomatic lesions. In addition, the production of IL-17 was higher in culture supernatants of PL-MNC isolated from lesions with a predominance of T cells, and the IL-17 concentration correlated with the proportion of CD3(+) and CD4(+) cells. There was a positive correlation between the levels of IL-17 and IL-8 in the group of symptomatic lesions. The relationship between these cytokines was additionally confirmed on the basis of augmented production of IL-8 by both PL-MNC and PB-MNC treated with IL-17. Our results suggest that IL-17, by stimulating the production of IL-8, may play a role in exacerbating inflammation within chronic periapical lesions.