CD4+ and CD8+ T cells producing Th1 and Th17 cytokines are involved in the pathogenesis of autoimmune orchitis.

Experimental autoimmune orchitis (EAO) is a useful model to study chronic testicular inflammation and infertility. EAO is characterized by severe damage of seminiferous tubules with germ cells that undergo apoptosis and sloughing. We previously reported an increase in CD4+ and CD8+ effector T cells in the testes of rats with EAO. Since cytokine patterns determine T cell effector functions, in the present work we analyzed the cytokines expressed by these cells during disease development. By flow cytometry, we detected an increase in the number of tumor necrosis factor-α (TNF) and interferon -γ (IFNG)-producing CD4+ T cells in the testis at EAO onset. As the severity of the disease progressed, these cells declined while CD8+ T cells producing TNF and IFNG increased, with the predominance of IFNG expression. As a novel finding, we identified by immunofluorescence CD4+ interleukin 17 (IL17)+ and CD8+ IL17+ cells in the testes of EAO rats, with CD4+ and CD8+ T cells predominating at the onset and in the chronic phase of EAO respectively. Moreover, IL17 (western blot) and IL23 content (ELISA) increased in EAO, with maximum levels in the chronic phase. These results suggest the involvement of CD4+ T helper (Th) 1 and Th17 subsets as co-effector cells governing EAO onset, as well as the central contribution of CD8+ T cells producing Th1 and Th17 cytokines in the maintenance of chronic inflammation. The expression of T-bet and RORγt (western blot) in the testis over the course of disease also supports the presence of Th1 and Th17 cells in the testes of EAO rats.