Regulatory T cells limit age-associated retinal inflammation and neurodegeneration

Abstract

Background Ageing is the principal risk factor for retinal degenerative diseases, which are the commonest cause of blindness in the developed countries. These conditions include age-related macular degeneration or diabetic retinopathy. Regulatory T cells play a vital role in immunoregulation of the nervous system by limiting inflammation and tissue damage in health and disease. Because the retina was long-considered an immunoprivileged site, the precise contribution of regulatory T cells in retinal homeostasis and in age-related retinal diseases remains unknown. Methods Regulatory T cells were selectively depleted in both young (2–4 months) and aged (18–23 months) FoxP3-DTR mice. We evaluated neuroretinal degeneration, gliosis, subretinal space phagocyte infiltration, and retinal pigmented epithelium morphology through immunofluorescence analysis. Subsequently, aged Treg depleted animals underwent adoptive transfer of both young and aged regulatory T cells from wild-type mice, and the resulting impact on neurodegeneration was assessed. Statistical analyses employed included the U-Mann Whitney test, and for comparisons involving more than two groups, 1-way ANOVA analysis followed by Bonferroni’s post hoc test. Results Our study shows that regulatory T cell elimination leads to retinal pigment epithelium cell dysmorphology and accumulation of phagocytes in the subretinal space of young and aged mice. However, only aged mice experience retinal neurodegeneration and gliosis. Surprisingly, adoptive transfer of young but not aged regulatory T cells reverse these changes. Conclusion Our findings demonstrate an essential role for regulatory T cells in maintaining age retinal homeostasis and preventing age-related neurodegeneration. This previously undescribed role of regulatory T cells in limiting retinal inflammation, RPE/choroid epithelium damage and subsequently photoreceptor loss with age, opens novel avenues to explore regulatory T cell neuroprotective and anti-inflammatory properties as potential therapeutic approaches for age-related retinal diseases.

Glia-Mediated Antigen Presentation In The Retina During Degeneration

“…However, we know that CD4 + T-cells are recruited to the parenchyma in mice with experimental ischemic retinopathy and laser-injuries and both models also involved glial activation (Conedera et al, 2023; Khanh Vu et al, 2020; Wagner et al, 2021). Interestingly, other recent publications implied the connection between resident immune cells and CD4 + T-cells showing that the depletion of CD4 + T-cells leads to the accumulation of pro-inflammatory microglia (Llorián-Salvador et al, 2024). Thus, resident immune cells can stimulate CD4 + T-cell migration to the damaged retina as well as T-cells can affect immune cell activation once they interplay with T-cells.…”