Recipient T cell TIM-3 and hepatocyte galectin-9 signalling protects mouse liver transplants against ischemia-reperfusion injury

Background & Aims By binding to T cell immunoglobulin mucin-3 (TIM-3) on activated Th1 cells, galectin-9 (Gal-9) negatively regulates Th1-type alloimmunity. Although T cells contribute to hepatic ischemia-reperfusion injury (IRI), it is unknown whether negative T cell-dependent TIM-3 co-stimulation may rescue IR-stressed orthotopic liver transplants from innate immunity-driven inflammation. Methods We used wild type (WT) and TIM-3 transgenic (Tg) mice (C57BL/6) as liver donors and recipients in a clinically-relevant model of hepatic cold storage (20 h at 4 °C in UW solution) and syngeneic orthotopic liver transplantation (OLT). Results Orthotopic liver transplants in WT or TIM-3Tg→TIM-3Tg groups were resistant against IR-stress, evidenced by preserved hepatocellular function (serum ALT levels) and liver architecture (Suzuki's score). In contrast, orthotopic liver transplants in WT or TIM-3Tg→WT groups were susceptible to IRI. TIM-3 induction in circulating CD4⁺ T cells of the recipient: (1) depressed T-bet/IFN-γ, while amplifying GATA3 and IL-4/IL-10 expression in orthotopic liver transplants; (2) promoted T cell exhaustion (PD-1, LAG-3) phenotype; and (3) depressed neutrophil and macrophage infiltration/function in orthotopic liver transplants. In parallel studies, we documented for the first time that Gal-9, a natural TIM-3 ligand, was produced primarily by and released from IR-stressed hepatocytes, both in vivo and in vitro. Moreover, exogenous recombinant Gal-9 (rGal-9) potentiated liver resistance against IRI by depressing T cell activation and promoting apoptosis of CD4⁺ T cells. Conclusions Harnessing TIM-3/Gal-9 signalling at the T cell-hepatocyte interface facilitates homeostasis in IR-stressed orthotopic liver transplants. Enhancing anti-oxidant hepatocyte Gal-9 potentiates liver IR-resistance. Negative regulation by recipient TIM-3⁺CD4⁺ cells provides evidence for cytoprotective functions of a discrete T cell subset, which should be spared when applying T cell-targeted immunosuppression in transplant recipients.