IL-17 producing γδ T cells are required for a controlled inflammatory response after bleomycin-induced lung injury

Background gamma delta T cells play a key role in the regulation of inflammatory responses in epithelial tissue, and in adaptive immunity, as gamma delta T cell deficient mice have a severely impaired capacity to clear lung pathogens. gamma delta T cells regulate the initial inflammatory response to microbial invasion and thereby protect against tissue injury. Here we examined the response of gamma delta T cells to lung injury induced by bleomycin, in an effort to study the inflammatory response in the absence of any adaptive immune response to a pathogen. Results. After lung injury by bleomycin, we localized the gamma delta T cells to the lung lesions. gamma delta T cells were the predominant source of IL-17 (as detected by flow cytometry and real-time PCR). Moreover, gamma delta T cell knockout mice showed a significant reduction in cellular infiltration into the airways, reduced expression of IL-6 in the lung, and a significant delay in epithelial repair. Conclusion. Mouse gamma delta T cells produce IL-17 in response to lung injury and are required for an organized inflammatory response and epithelial repair. The lack of gamma delta T cells correlates with increased inflammation and fibrosis.