Adenosine A2A receptor-mediated interactions between Th1+ T cells and the choroid plexus epithelium via IFN-γ signalling control T-Cell infiltration in experimental autoimmune encephalomyelitis.

Background: Adenosine A_2A receptor (A_2AR) antagonists have been consistently demonstrated to protect against multiple sclerosis (MS) pathology, but A_2AR knockout (A_2AR^-/-) mice exhibit exacerbated immune injury, raising concerns regarding the use of A_2AR antagonists for MS treatment. Here, we revealed the critical involvement of A_2AR-mediated interactions between Th1⁺ T cells and the choroid plexus (ChP) epithelium in the pathology of experimental autoimmune encephalomyelitis (EAE).

Methods: We assessed the effects of A_2AR knockout on ChP gateway activity and the interferon gamma (IFN-γ)-secreting capacity of Th1⁺ T cells in an EAE model by immunofluorescence, qPCR and flow cytometry (FCM). We also investigated the effects of A_2AR-mediated interactions between Th1⁺ T cells and the ChP epithelium on ChP gateway activity in vivo via intracerebroventricular (ICV) injection of Th1⁺ T cells and in vitro via coculture of ChP epithelial cells and splenic Th1⁺ T cells. We further knocked down IFN-γ receptor 1 (IFNGR1) specifically in the ChP of A_2AR^-/- mice via ICV injection of AAV2/5-shRNA (IFNGR1) to disrupt the interactions between Th1⁺ T cells and the ChP epithelium and thus assess the roles of these interactions in the development of EAE pathology.

Results: A_2AR knockout disrupted the ChP barrier and increased T-cell infiltration across the ChP in EAE model mice. Coculture of splenic Th1⁺ T cells and ChP epithelial cells revealed that A_2AR knockout in ChP epithelial cells strengthened the ChP barrier and attenuated T-cell migration, whereas A_2AR knockout in Th1⁺ T cells increased the accumulation of Th1⁺ T cells in the ChP via the secretion of IFN-γ. Consistent with the coculture results, ICV injection of activated splenic Th1⁺ T cells from A_2AR^-/- mice increased the accumulation of T cells in the ChP to a greater extent than did injection of Th1⁺ T cells from A_2AR^+/+ mice. This effect was due to the increased secretion of IFN-γ in A_2AR^-/- mice compared with A_2AR^+/+ mice. Finally, ChP-specific knockdown of IFNGR1 attenuated A_2AR knockout-induced T-cell infiltration, brain inflammation and EAE pathology.

Conclusion: A_2AR-mediated interactions between Th1⁺ T cells and the ChP epithelium via the secretion of IFN-γ from CD4⁺ T cells and the binding IFN-γ to IFNGR1 in the ChP epithelium control immune cell invasion and the development of EAE pathology in A_2AR^-/- mice.