IL1ß-dependent extravasation of pre-existing lung-restricted autoantibodies activates complement to promote primary graft dysfunction

Pre-existing lung restricted autoantibodies (LRA) are associated with a higher incidence of primary graft dysfunction (PGD) although it remains unclear whether LRA can drive its pathogenesis. In syngeneic murine left lung transplant recipients, pre-existing LRA worsened graft dysfunction, which was evident by impaired gas exchange, increased pulmonary edema, and activation of damage-associated pathways in lung epithelial cells. LRA-mediated injury was distinct from ischemia-reperfusion injury since deletion of donor non-classical monocytes as well as host neutrophils could not prevent graft dysfunction in LRA-pretreated recipients. Whole LRA IgG molecule was necessary for lung injury which was mediated by the classical and alternative complement pathways and reversed by complement inhibition. However, deletion of Fc receptors in donor macrophages or mannose-binding lectin proteins failed to rescue lung function. LRA- mediated injury was localized to the transplanted lung and dependent on IL1ß-mediated permeabilization of pulmonary vascular endothelium which allowed extravasation of antibodies. Genetic deletion or pharmacological inhibition of IL1R in the donor lungs prevented LRA-induced graft injury. In humans, pre-existing LRA was an independent risk factor for severe PGD and could be treated with plasmapheresis and complement blockade. We conclude that pre-existing LRA can compound ischemia-reperfusion injury to worsen PGD for which complement inhibition may be effective. Overall design: Single-cell suspensions from 24 hours post-transplant allografts from isotype or LRA treated mice .