P2Y2R Deficiency Attenuates Experimental Autoimmune Uveitis Development

We aimed to study the role of the nucleotide receptor P2Y₂R in the development of experimental autoimmune uveitis (EAU). EAU was induced in P2Y₂^+/+ and P2Y₂^-/- mice by immunization with IRBP peptide or by adoptive transfer of in vitro restimulated semi-purified IRBP-specific enriched T lymphocytes from spleens and lymph nodes isolated from native C57Bl/6 or P2Y₂^+/+ and P2Y₂^-/- immunized mice. Clinical and histological scores were used to grade disease severity. Splenocytes and lymph node cell phenotypes were analyzed using flow cytometry. Semi-purified lymphocytes and MACS-purified CD4⁺ T lymphocytes from P2Y₂^+/+ and P2Y₂^-/- immunized mice were tested for proliferation and cytokine secretion. Our data show that clinical and histological scores were significantly decreased in IRBP-immunized P2Y₂^-/- mice as in P2Y₂^-/- mice adoptively transfered with enriched T lymphocytes from C57Bl/6 IRBP-immunized mice. In parallel, naïve C57Bl/6 mice adoptively transferred with T lymphocytes from P2Y₂^-/- IRBP-immunized mice also showed significantly less disease. No differences in term of spleen and lymph node cell recruitment or phenotype appeared between P2Y₂^-/- and P2Y₂^+/+ immunized mice. However, once restimulated in vitro with IRBP, P2Y₂^-/- T cells proliferate less and secrete less cytokines than the P2Y₂^+/+ one. We further found that antigen-presenting cells of P2Y₂^-/- immunized mice were responsible for this proliferation defect. Together our data show that P2Y₂^-/- mice are less susceptible to mount an autoimmune response against IRBP. Those results are in accordance with the danger model, which makes a link between autoreactive lymphocyte activation, cell migration and the release of danger signals such as extracellular nucleotides.