Abstract: Primary open angle glaucoma (POAG) is a potentially blinding ocular disease that affects 60 million people world-wide. Reduction of IOP is currently the only glaucoma treatment, but fails to preserve vision in a significant fraction of patients, suggesting that other –currently untreated- factors contribute to the disease. Therefore, there is a critical need to identify these additional pathomechanisms to aid the development of new therapeutic approaches that directly support survival and function of retinal ganglion cells (RGC). Our recently published studies have demonstrated that adoptive transfer of T-cells from glaucomatous mice into normal recipients causes RGC loss in the recipients. We have also demonstrated that the absence of T- and B-cells profoundly protects RGC in a mouse glaucoma model. Preliminary data included in this application demonstrates that peripheral blood mononuclear cells (PBMC) of glaucoma patients contain a higher fraction of CD4 cells synthesizing TNFα and exhibit a higher activation state than those of controls. We further demonstrate that glaucoma PBMC have a heightened propensity to damage RGC in an ex vivo assay when compared to controls. Together, these findings strongly suggest that T-cell mediated damage is one of the mechanisms contributing to RGC loss in both animal models and in human patients. This project is designed with the long-term goal to determine whether modulation of immune responses provides vision saving benefits to glaucoma patients. The objective of this application is to establish which subtype of CD4 T-cells mediates damage in the glaucoma retina and to determine the functional significance of CD4 cell derived TNFα. To test our novel hypothesis we will employ a transgenic mouse model of myocilin-associated spontaneous glaucoma that we previously developed (Tg-MYOCY437H) containing an inducible Tnf knockout allele. We have also developed a novel in vitro assay allowing the quantitation of the cytotoxic activity of patient PBMC targeted toward RGC. Finally we propose to determine the activities T cells extravasated in the glaucoma retina, as well as those in lymph nodes and PBMC by establishing detailed gene transcription profiles. Experimental proof that CD4 T-cell mediated mechanisms contribute to vision loss in patients would establish new targets for the medical treatment of glaucoma. These in turn will pave a way for future clinical studies with the ultimate aim of preserving the sight and improving the quality of life of patients with primary open angle glaucoma.