CD154 blockade alters innate immune cell recruitment and programs alloreactive CD8+ T cells into KLRG-1(high) short-lived effector T cells.

Ivana R Ferrer,Mingqing Song,Maylene E Wagener,Mandy L Ford

doi:10.1371/journal.pone.0040559

Abstract

CD154/CD40 blockade combined with donor specific transfusion remains one of the most effective therapies in prolonging allograft survival. Despite this, the mechanisms by which these pathways synergize to prevent rejection are not completely understood. Utilizing a BALB/c (H2-Kd) to B6 (H2-Kb) fully allogeneic skin transplant model system, we performed a detailed longitudinal analysis of the kinetics and magnitude of CD8+ T cell expansion and differentiation in the presence of CD154/CD40 pathway blockade. Results demonstrated that treatment with anti-CD154 vs. DST had distinct and opposing effects on activated CD44high CD62Llow CD8+ T cells in skin graft recipients. Specifically, CD154 blockade delayed alloreactive CD8+ T cell responses, while DST accelerated them. DST inhibited the differentiation of alloreactive CD8+ T cells into multi-cytokine producing effectors, while CD40/CD154 blockade led to the diminution of the KLRG-1low long-lived memory precursor population compared with either untreated or DST treated animals. Moreover, only CD154 blockade effectively inhibited CXCL1 expression and neutrophil recruitment into the graft. When combined, anti-CD154 and DST acted synergistically to profoundly diminish the absolute number of IFN-γ producing alloreactive CD8+ T cells, and intra-graft expression of inflammatory chemokines. These findings demonstrate that the previously described ability of anti-CD154 and DST to result in alloreactive T cell deletion involves both delayed kinetics of T cell expansion and differentiation and inhibited development of KLRG-1low memory precursor cells.

Highlights

Current immunosuppressive regimens in organ transplantation require life-long administration and result in off-target toxicities such as nephrotoxicity and cardiovascular and metabolic complications [1]
We examined the individual contributions of donor specific transfusion (DST) and anti-CD154 on innate and adaptive cell recruitment, the accumulation of inflammatory chemokines within the allograft, and the programming of alloreactive CD8+ T cell responses
This well-established regimen consists of BALB/c DST administered in conjunction with anti-CD154 monoclonal antibody treatment at the time of BALB/c skin transplantation onto naıve B6 recipients [6]

Summary

Introduction

Current immunosuppressive regimens in organ transplantation require life-long administration and result in off-target toxicities such as nephrotoxicity and cardiovascular and metabolic complications [1]. Considering these significant co-morbidities, much work over the years has focused on the development of novel modes of immunosuppression. The development of costimulation blocking molecules has been the basis for research by several groups to target and inhibit the full activation of alloantigen-specific T cells at the time of transplantation. One of the most effective pathways for therapeutic intervention is the CD154/CD40 pathway, blockade of which results in profound inhibition of graft rejection and in some models the induction of transplantation tolerance [2,3,4]. Understanding the altered differentiation programs initiated in alloreactive T cell populations under conditions of CD154 blockade remains an important goal in the ongoing pursuit to harness the therapeutic potential of this pathway

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