Hedgehog costimulation during ischemia-reperfusion injury potentiates cytokine and homing responses of CD4⁺ T cells

Introduction: Ischemia reperfusion injury (IRI) confers worsened outcomes and is an increasing clinical problem in solid organ transplantation. Previously, we identified a "Ptch(Hi)" T-cell subset that selectively received costimulatory signals from endothelial cell-derived Hedgehog (Hh) morphogens to mediate IRI-induced vascular inflammation. Methods: Here, we used multi-omics approaches and developed a humanized mouse model to resolve functional and migratory heterogeneity within the Ptch(Hi) population. Results: Hh-mediated costimulation induced oligoclonal and polyclonal expansion of clones within the Ptch(Hi) population, and we visualized three distinct subsets within inflamed, IRI-treated human skin xenografts exhibiting polyfunctional cytokine responses. One of these Ptch(Hi) subsets displayed features resembling recently described T peripheral helper cells, including elaboration of IFN-y and IL-21, expression of ICOS and PD-1, and upregulation of positioning molecules conferring recruitment and retention within peripheral but not lymphoid tissues. Ptch(Hi) T cells selectively homed to IRI-treated human skin xenografts to cause accelerated allograft loss, and Hh signaling was sufficient for this process to occur. Discussion: Our studies define functional heterogeneity among a Ptch(Hi) T-cell population implicated in IRI.