Endothelial Cell–Derived Interleukin-18 Released During Ischemia Reperfusion Injury Selectively Expands T Peripheral Helper Cells to Promote Alloantibody Production

Abstract

Background: Ischemia reperfusion injury (IRI) predisposes to the formation of donor-specific antibodies, a factor contributing to chronic rejection and late allograft loss. Methods: We describe a mechanism underlying the correlative association between IRI and donor-specific antibodies by using humanized models and patient specimens. Results: IRI induces immunoglobulin M–dependent complement activation on endothelial cells that assembles an NLRP3 (NOD-like receptor pyrin domain-containing protein 3) inflammasome via a Rab5-ZFYVE21-NIK axis and upregulates ICOS-L (inducible costimulator ligand) and PD-L2 (programmed death ligand 2). Endothelial cell–derived interleukin-18 (IL-18) selectively expands a T-cell population (CD4+CD45RO+PD-1 hi ICOS+CCR2+CXCR5–) displaying features of recently described T peripheral helper cells. This population highly expressed IL-18R1 and promoted donor-specific antibodies in response to IL-18 in vivo. In patients with delayed graft function, a clinical manifestation of IRI, these cells were Ki-67+IL-18R1+ and could be expanded ex vivo in response to IL-18. Conclusions: IRI promotes elaboration of IL-18 from endothelial cells to selectively expand alloreactive IL-18R1+ T peripheral helper cells in allograft tissues to promote donor-specific antibody formation.

Complement Membrane Attack Complex

“…13 IL-1b, processed and released by MACactivated ECs, initiates autocrine/paracrine signaling and induces up-regulation of proinflammatory genes, including chemokines, cytokines, and adhesion molecules, through activation of canonical NF-kB pathway. 13 MAC induction of the EC NLRP3 inflammasome also led to IL-18 secretion from ECs, and IL-18 can act to selectively expand alloreactive peripheral helper T cells, an IL-21eproducing T-cell subset, 50 that may act on a variety of other cell types, including B cells and endothelium. The net result of MAC-induced IL-1b (and possibly IL-18) secretion is to provide endothelium with an enhanced capacity to locally recruit and activate leukocytes, including alloreactive effector memory T cells.…”

“…Mechanistically, the IgM-dependent MAC activation of human ECs induced by IRI leads to IL-18 secretion and selective expansion of IL-21esecreting peripheral helper T cells that promote B-cell production of DSA. 50…”

An update on the regulatory mechanisms of NLRP3 inflammasome activation

“… 100 , 101 Ischemia-reperfusion injury (IRI) results in immunoglobulin M (IgM)-dependent complement system activation that induces NLRP3 inflammasome assembly in endothelial cells. 151 The internalization of MAC in IFN-γ-primed human endothelial cells causes NLRP3 translocation into endosomes and leads to endosomal NF-κB-inducing kinase (NIK)-dependent inflammasome assembly, resulting in complement-associated pathologies. 152 Several studies have revealed that the C5a/C5aR pathway promotes activation of the NLRP3 inflammasome through amplification of dsRNA-dependent PKR expression in macrophages, suggesting that PKR is an important NLRP3-activating factor.…”

Minimizing Ischemia Reperfusion Injury in Xenotransplantation

“…Each pathway leads to formation of the C5b-9 ‘membrane attack complex’, the final common complement activation pathway which physically disrupts the cell membrane, overwhelming the ability of ion channels to maintain membrane polarization and osmolar gradients, resulting in cell death ( 31 ). Upstream byproducts of complement activation such as C5a and C3a are chemoattractants for neutrophils and macrophages which can lead to tissue inflammation ( 68 , 72 ). Additionally, C3a and C5a can bind a variety of G protein coupled receptors as well as TLR2, which trigger NF-κB activation and the formation of the inflammasome ( 80 , 81 ).…”