Abstract
Purpose :
Experimental autoimmune uveitis (EAU) is used to gain a better understanding of human autoimmune uveitis. Ocular antigen specific regulatory T cells (Tregs) are found in the spleen of EAU-resolved mice (post-EAU). Post-EAU Tregs prevent relapse and require the adenosine 2A receptor (A2Ar). Previous work has shown that a subset of uveitis patients have a reduced capacity to generate Tregs when stimulated through A2Ar. Tregs migrate into the eye at the onset of EAU, but A2Ar-/- mice show a delay of Treg infiltration into the eye during EAU. Distinct A2Ar-dependent post-EAU Treg populations that express PD-1 or TIGIT have been identified, but the mechanism of induction through A2Ar has not been determined. STING is activated by cGAS to activate innate immunity. However, STING can also impair T cell immunity by promoting Tregs and facilitating Treg infiltration. We examined PD-1 and TIGIT cells from WT and A2Ar-/- mice during EAU to determine if STING is involved in the A2Ar-dependent induction and migration of Tregs into the eye.
Methods :
We immunized WT mice and A2Ar-/- mice for EAU and collected Treg cells at the onset and just before resolution of EAU. Nanostring analysis was done to determine the expression profile at the onset of EAU when Tregs first migrate into the eye. Flow cytometry analysis was done at the resolution phase to determine co-expression of STING on PD-1+ and TIGIT+ Tregs.
Results :
Nanostring analysis revealed significantly lower STING and cGAS expression in Tregs from A2Ar-/- mice compared to WT mice at the onset of EAU. We observed STING in all TIGIT+ Tregs, but STING was not expressed in the PD-1+ Tregs.
Conclusions :
These results identified a potential novel mechanism for the induction of A2Ar-dependent TIGIT+ Tregs through the STING pathway. Further, it suggests differential mechanisms for the induction of PD-1+ Tregs and TIGIT+ Tregs. Additionally, this mechanism may also be involved in the infiltration of Tregs into the eye at the onset of EAU. Insufficient activation of the STING pathway may result in a reduced capacity to generate Tregs, as observed in some uveitis patients. Therefore, this work provides a potential explanation why stimulation of A2Ar does not generate Tregs in uveitis patients. Importantly, it suggests multiple mechanisms to generate different Treg populations may be utilized as a therapeutic option.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.