A2Ar-dependent PD-1+ and TIGIT+ Treg cells have distinct homing requirements to suppress autoimmune uveitis in mice

The proper function of regulatory T cells (Tregs) to suppress inflammation requires homing to the correct tissue site. Resolution of autoimmune uveitis generates distinct programmed death receptor 1 (PD-1⁺) and T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT⁺) Tregs in an adenosine 2A receptor (A2Ar)-dependent manner found in the spleen. Where and how these Tregs migrate from the spleen to prevent uveitis is not known. In this work, we show that A2Ar-dependent Tregs migrated to the eye and secondary lymphoid tissue and expressed chemokine receptor (CCR)6 and CCR7. Suppression of autoimmune uveitis required CCR6 and CCR7 expression for TIGIT⁺ Tregs but not PD-1⁺ Tregs. Moreover, stimulation of A2Ar on T cells from patients showed a decreased capacity to induce TIGIT⁺ Tregs that expressed CCR6 or CCR7, and PD-1⁺ Treg that expressed CCR6. This work provides a mechanistic understanding of the homing requirements of each of these Treg populations. Importantly, this work is clinically relevant because patients with chronic autoimmune uveitis are unable to induce the Treg populations identified in mice that home to the target tissue.