OVERALL – ABSTRACT Orthotopic liver transplantation (OLT) is the accepted treatment in patients with end-stage liver failure and those with tumors of hepatic origin. However, the organ shortage has prompted the use of extended criteria donors, which are particularly susceptible to ischemia-reperfusion injury (IRI). The overarching hypothesis of this P01 renewal is that IRI in OLT results from impaired regulation between donor liver-specific and host-derived innate immunity. The project and core objectives, functioning in a highly synergistic manner, are to 1/ identify new target molecules for improving donor liver quality (organ rejuvenation); 2/ provide novel therapeutic means against acute IR-stress while promoting inflammation resolution (homeostatic reparation); and 3/ prevent sustained/ chronic inflammation to mitigate alloimmunity and improve outcomes (tolerance induction). Project 1 focuses on a newly discovered CEACAM1 (CC1) negative checkpoint regulation of IR-triggered innate immune activation/sterile inflammation in the mechanism of donor liver rejuvenation. Aim 1 and 2 will delineate mechanisms by which enforced CC1 alternative splicing in the donor liver (S-isoform), or the recipient-derived neutrophils (L-isoform) exert anti-inflammatory/cytoprotective functions in mouse IRI-OLT (synergy: Project 2/3). Aim 3 will elucidate whether/how modulation of hepatic CC1 might improve the function of discarded human livers (deemed untransplantable) when subjected to normothermic machine preservation (synergy: Project 3). Project 2 defines mechanisms by which reprogramming of IR-stressed mouse liver-infiltrating macrophages and resident heterogeneic KCs orchestrate the restoration of hepatic tissue homeostasis. In synergy with Project 1/3, Aim 1 will determine the functional mechanisms by which embryonic vs. monocyte-derived KCs promote liver IR-inflammation resolution. Aim 2 will define MerTK-mediated pro-resolution effector pathways in the liver- resident KCs. Aim 3 will dissect the roles of KCs in OLT settings and whether/how liver inflammation resolution and its kinetics impact the activation of alloimmunity and putative acquisition of transplant tolerance. Project 3 dissects the innate immune DAMPs and associated cofactors/PRRs driving myeloid cell plasticity in human IRI-OLT patients. In synergy with Project 1/2, Aim 1 will determine the TLR7/NOD2 and TLR9 ligands and signaling pathways mediating differential polarization of regulatory vs. inflammatory macrophages and crosstalk with T cells. Aim 2 will assess the therapeutic potential of PRR inhibition/preconditioning to mitigate myeloid cell activation and OLT-IRI. Aim 3 will elucidate the impact of DAMP/PRR endotypes on the generation of alloimmunity and graft outcome, and potential transplantation tolerance acquisition. The Projects will be supported by an Administrative Core (Core A), Mouse/Human Liver Surgery Core (Core B), and Computational/Biostatistics Core (Core C). This P01 unif...