PROJECT 1 SUMMARY Primary graft dysfunction (PGD) affects over 50% of recipients within the first 24-72 hours after lung transplantation. PGD is the dominant risk for post-operative mortality, transplant-associated multi-organ dysfunction, and chronic lung allograft rejection. We found that 30% of patients with chronic end-stage disease develop autoantibodies against lung-restricted self-antigens, collagen type V and k-alpha 1 tubulin. The presence of LRA in lung transplant recipients was strongly associated with the development of PGD and CLAD. Using a murine model of lung transplantation, we showed that recipient mice harboring LRA have complement activation, neutrophil recruitment, a lower PaO2/FIO2 and worsened lung injury, all clinical hallmarks of PGD. Our published and preliminary data suggest important interactions between LRA, donor derived NCM and recipient derived CM in determining the severity of lung injury after lung transplantation. We found that LRA bind Fc receptors on donor derived NCM to promote their retention in the allograft and activation. This enhances the recruitment of CM to the allograft which release IL-1β and matrix metalloproteinase-8 (MMP8), liberating sequestered and immune privileged self-antigens and exposing their immunogenic epitopes, enabling the extravasated LRA to form immune complexes. The resulting immune complexes activate complement to exacerbate lung injury in the first 24 hours after lung transplantation. Further preliminary data suggest LRA immune complexes activate donor derived NCM to release CXCL2 and promote neutrophil recruitment via a pathway that requires Src, PI3K and BTK, but is independent of the TLR2/4/MyD88 activated by DAMPs. This results in delayed lung injury 48 to 72 hours after transplant. We will test the hypothesis that pre-existing LRA interact with donor derived NCM and recipient CM to worsen PGD via complement dependent and independent pathways in two interrelated aims: Aim 1. To determine the mechanisms through which LRA activate NCM to worsen PGD. Aim 2. To determine the role of IL-1β and MMP-8 released from recipient CM in the cleavage of sequestered self-antigens and their binding to LRA. In collaboration Project 2, we will examine the role of acid aspiration in the formation of de novo LRA and epitope spreading, in collaboration with Project 3, we will determine whether LRA enhance the recruitment or retention of profibrotic monocyte derived alveolar macrophages. In collaboration with Project 4, we will determine whether worsening of PGD induced by LRA drive mitochondrial dysfunction in the epithelium to induce pathologic ISR activation that prevents repair. These studies will provide insights into the mechanisms by which LRA worsen PGD and link them to clinically applicable strategies that can be rapidly translated to the care of patients requiring lung transplantation.