Development of uveitis in a mouse model of spontaneous autoimmunity correlates with frequency of autoantigen-specific regulatory T cells

B6 AireGW/+Lyn-/-mice are a model of spontaneously autoimmunity in which 50% of mice develop uveitis by 9 weeks of age, and the remaining mice do not develop autoimmunity. Uveitis results from CD4+ T cells responding to the retina protein interphotoreceptor retinoid-binding protein (IRBP). To define cellular mechanisms that determine whether mice developed autoimmunity or not, we did single-cell RNA sequencing (scRNA-seq) of eye-draining lymph node (LN) CD4+T cells that recognize the P2 epitope of IRBP (amino acid 271-290). Uniform manifold approximation and projection (UMAP) analysis showed that these CD4+T cells included distinct subsets that were Teff, Tfh, Il7r_hi, T_prolif, T_trans, Ifit1_hi and Tregs, with the Treg population being overrepresented in mice without disease. In mice without uveitis, depletion of Treg by treatment of AireGW/+Lyn-/- Foxp3DTR+/Y mice with Diphtheria toxin resulted in rapid expansion of P2–specific CD4+T cells in the draining LN, development of inflammation in the retina, and immune activation in other locations leading to lethality. In summary, those results indicated that expansion of P2-specific CD4+Treg cells promote the development of uveitis in AireGW/+Lyn-/-mice.