Ischemia augments alloimmune injury through IL-6-driven CD4+ alloreactivity

Mayuko Uehara,Osman Yilmam,Mine Yilmaz,Reza Abdi,Stefan G Tullius,Vivek Kasinath,Ye Xiaqun,Li Dai,Indira Guleria,Zhabiz Solhjou,Naima Banouni,Omar H Maarouf,Takaharu Ichimura,Martina M Mcgrath,Shunsuke Ohori,Paulo N Martins,Paolo Fiorina

doi:10.1038/s41598-018-20858-4

Abstract

Ischemia reperfusion injuries (IRI) are unavoidable in solid organ transplantation. IRI augments alloimmunity but the mechanisms involved are poorly understood. Herein, we examined the effect of IRI on antigen specific alloimmunity. We demonstrate that ischemia promotes alloimmune activation, leading to more severe histological features of rejection, and increased CD4+ and CD8+ T cell graft infiltration, with a predominantly CD8+ IFNγ+ infiltrate. This process is dependent on the presence of alloreactive CD4+ T cells, where depletion prevented infiltration of ischemic grafts by CD8+ IFNγ+ T cells. IL-6 is a known driver of ischemia-induced rejection. Herein, depletion of donor antigen-presenting cells reduced ischemia-induced CD8+ IFNγ+ allograft infiltration, and improved allograft outcomes. Following prolonged ischemia, accelerated rejection was observed despite treatment with CTLA4Ig, indicating that T cell costimulatory blockade failed to overcome the immune activating effect of IRI. However, despite severe ischemic injury, treatment with anti-IL-6 and CTLA4Ig blocked IRI-induced alloimmune injury and markedly improved allograft survival. We describe a novel pathway where IRI activates innate immunity, leading to upregulation of antigen specific alloimmunity, resulting in chronic allograft injury. Based on these findings, we describe a clinically relevant treatment strategy to overcome the deleterious effect of IRI, and provide superior long-term allograft outcomes.

Highlights

Ischemia reperfusion injury (IRI) is an inevitable consequence of transplantation
We have previously shown that allograft-resident dendritic cells (DC) increase IL-6 production in the setting of ischemia, and blockade of IL-6 improves allograft outcomes[18]
We have previously reported that ischemia promotes autophagy and increased IL-6 production by ischemic allograft resident DCs18

Summary

Introduction

Ischemia reperfusion injury (IRI) is an inevitable consequence of transplantation. IRI leads to a cascade of intra-graft inflammation, and initiates immune activation within the transplanted organ[1]. The effector mechanism linking IL-6, allospecific T cell activation and chronic rejection has not been identified We used both a typical Class I MHC mismatch model, and an antigen-specific TCR transgenic model of cardiac transplantation to comprehensively examine the impact of IRI on antigen-specific alloreactive CD4+ and CD8+ T cells. We identified allospecific CD4+ T cells as critical mediators of enhanced alloimmune reactivity following IRI Despite their central role, costimulatory blockade of CD4+ T cells with CTLA4Ig failed to overcome the negative effect of prolonged ischemia on allograft survival. Addition of anti-IL-6 therapy to CTLA4Ig overcame the effect of severe allograft ischemia, leading to long-term graft survival in a full MHC mismatch model This approach represents a clinically applicable treatment model to reduce early immune activation by IRI and improve long-term allograft outcomes

Methods

Results

Conclusion