Cellular mechanisms of dihydrotestosterone in autoreactive T cells

The preponderance for females to develop autoimmune diseases, more than in males, suggests that hormonal changes can act as important triggers in those affected. In our studies, we used experimental autoimmune encephalomyelitis (EAE) induced with proteolipid protein (PLP) 139-151 in SJL mice as a disease model for multiple sclerosis in humans. In this model, gender-differences are well-documented in that only females show a chronic relapsing-remitting type of paralysis, whereas in males, the disease-course is restricted to monophasic form. Furthermore, sex hormones, in particular, dihydrotestosterone (DHT), have been shown to alleviate EAE-severity, but the target cell types for DHT are unknown. Since CD4 T cells are indispensable mediators of EAE, we tested a hypothesis that their generation and functionalities might be different between genders. To this end, we used major histocompatibility complex class II dextramers for PLP 139-151 that permitted us to determine gender-differences in antigen-specific T cell responses in SJL mice. We demonstrate that PLP-reactive T cell responses generated in male and female mice did not differ. Likewise, similar proportions of PLP-specific T cells were found to infiltrate into the brains of EAE mice in both the genders. Furthermore, by establishing a novel in situ dextramer straining, we demonstrate that comparable frequencies of PLP-specific CD4 T cells to be scattered all through the brain tissues in both the genders. In addition, cytokine analysis did not reveal any deviation, rather, production of all cytokines tested namely, T helper (Th) 1, Th2 and Th17 cytokines were similar between genders. All of these observations rule out the defects, if any, with the generation, expansion and migration of antigen-specific T cells in both the genders. Finally, we established an in vitro system to understand the mechanistic basis for DHT-effects. These studies led us to conclude that DHT induces cell death in autoreactive T cells non-specifically as both antigen-responsive and bystander cells were equally affected. Unexpectedly, induction of anti-inflammatory, Th2 response was absent in DHT-treated cultures. Finally, we provide evidence that DHT-induced cell death was associated with autophagy, and dissecting this complex association may provide opportunities to identify DHT-responsive molecules that affect both the processes