CONICET | Buscador de Institutos y Recursos Humanos

Experimental autoimmune orchitis (EAO) is a useful model to study chronic testicular inflammation and infertility. EAO is characterized by an interstitial lymphomononuclear cell infiltrate and a severe damage of seminiferous tubules (ST) that undergo apoptosis and sloughing. We previously reported an increased number of infiltrating Foxp3+ regulatory T cells (Tregs) in the testis of EAO rats. Clusters of Foxp3+ cells were observed in the subalbuginea area of the testicular interstitium, in close proximity to damaged ST. In the present work, we analyzed the suppressive and proliferative capacity of Foxp3+ Tregs in the testis of rats undergoing autoimmune orchitis. EAO was induced by active immunization with testicular homogenate and adjuvants. Control (C) rats immunized with adjuvants and normal (N, non-treated) rats were also used. For functional analysis, CD4+ CD25high T cells containing more than 90% of Foxp3+ cells were isolated from testis draining lymph nodes of N, C and EAO rats by FACS sorting and analyzed for their in vitro suppressive activity. All groups of Tregs were found to suppress effector T cell proliferation induced by testicular antigens. However, EAO Tregs were more efficient than those of N and C rats (suppressive activity, N Tregs: 28%, C Tregs: 28%, EAO Tregs: 61%, data are representative of three independent experiments). In addition, Tregs express TGF-â1. By bromodeoxiuridine incorporation assay we detected an increased number of proliferating Foxp3+ Tregs in the testis of EAO compared to N and C rats (N: 0,09±0,01; C: 0,18±0,01; E: 1,8±0,2 (x105)*, *p<0,001). Overall results suggest that functional Tregs infiltrate EAO testis, locally proliferate and produce TGF-â1 in the inflamed organ. However, as the autoimmune damage occurs we speculate that cytokines present in the inflamed testis render effector T cells resistant to suppressive effect of Tregs.