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

Abstract

Abstract 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 Ly6c1hi, Pdcd1hi and Treg, with the Treg population being overrepresented in the mice without disease. Pseudotime analysis indicated that the Ly6c1hi T cell subset represented an earlier stage in activation, whereas the Pdcd1hi subset represented a later stage. The two types of effector CD4+ T cells of mice with and without disease largely clustered together relative to their gene expression. Similar analysis of P2-specific CD4+ T cells from retinas with inflammation indicated a progression from proliferative (Mki67hi) cells to a Lag3hi subset to a Lag3hi/Pdcd1hi subset. 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. Ongoing experiments are further testing the hypothesis that the fraction of Treg within the IRBP-specific CD4+ T cells determines whether or not these genetically susceptible mice develop eye-specific autoimmunity. Supported by AI138479