IL-6 blockade prevents costimulation blockade-resistant allograft rejection by promoting intragraft regulation in T cell-depleted recipients [FFPE]

The efficacy of costimulation blockade (CTLA4Ig/belatacept) in transplantation is reduced by an increased incidence of T cell-mediated rejection, which also persists after induction therapy with anti-thymocyte globulin (ATG). Herein, we investigate why ATG fails to prevent costimulation blockade-resistant rejection and how this barrier can be overcome. ATG did not prevent graft rejection in a murine heart transplant model of CTLA4Ig therapy and induced a pro-inflammatory cytokine environment. While ATG improved the balance between Tregs and effector T cells in the peripheral compartment, it had no such effect within cardiac allografts, which showed signs of inflammation. Neutralizing IL-6 alleviated inflammation, increased intragraft Treg frequencies long-term, and enhanced intragraft IL-10 and Th2 cytokine expression. IL-6 blockade together with ATG led to long-term, rejection-free heart graft survival under CTLA4Ig therapy. Combining ATG with IL-6 blockade prevents costimulation blockade-resistant rejection, thereby eliminating a major impediment to clinical use of costimulation blockers in transplantation. to investigate the effects of IL-6 blockade on intragraft inflammation, we performed gene expression profiling of data obtained via RNAseq of FFPE tissue sections of fully mismatched murine cardiac allografts explanted from recipients treated with or without IL-6 blockade isolated 14 days after transplantation.

共刺激阻断疗法（costimulation blockade，涵盖CTLA4Ig/贝拉西普belatacept）在器官移植中的疗效，会因T细胞介导的排斥反应发生率升高而降低，且该排斥反应在抗胸腺细胞球蛋白（anti-thymocyte globulin, ATG）诱导治疗后仍持续存在。本研究旨在探究ATG无法预防共刺激阻断剂抵抗性排斥反应的原因，以及如何克服这一临床障碍。在CTLA4Ig治疗的小鼠心脏移植模型中，ATG未能抑制移植物排斥反应，反而诱导了促炎细胞因子微环境。尽管ATG可改善外周循环中调节性T细胞（Tregs）与效应T细胞的平衡，但在出现炎症迹象的心脏移植物内却未发挥此类作用。中和白细胞介素-6（IL-6）可减轻炎症、长期提升移植物内Treg细胞比例，并增强移植物内IL-10与Th2型细胞因子的表达。在CTLA4Ig治疗方案下，联合IL-6阻断与ATG可实现心脏移植物的长期无排斥存活。联合ATG与IL-6阻断可预防共刺激阻断剂抵抗性排斥反应，从而消除移植领域中共刺激阻断剂临床应用的一大主要障碍。为探究IL-6阻断对移植物内炎症的影响，本研究对移植后14天采集的、经或未经IL-6阻断处理的受体体内完全错配的小鼠心脏移植物的福尔马林固定石蜡包埋（FFPE）组织切片进行RNA测序（RNAseq），并对所得数据开展基因表达谱分析。