Bradford C Bemiss, Chad A WittDepartment of Internal Medicine, Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St Louis, MO, USA: Chronic rejection is a major cause of death after the first year following lung transplantation. Bronchiolitis obliterans is the most common pathologic finding on biopsy, characterized by fibrous granulation tissue, which obliterates the lumen of the bronchiole. Clinically, in the absence of tissue for pathology, BO syndrome refers to a progressive irreversible drop in the forced (...) expiratory volume in 1 second. Recently, a broader definition of chronic rejection, termed "chronic lung allograft dysfunction", has been used to encompass a more inclusive definition of posttransplant dysfunction. Recently, the lung transplant community has come to realize that chronic rejection may be the final common result after repetitive epithelial insults. Acute rejection, infection, and alloreactivity to mismatched HLA antigens are a few of these insults that damage the surface of the bronchioles. Recent evidence of autoimmunity to the normally hidden structural proteins collagen V and K-α1 tubulin have been correlated with a BO phenotype as well, perhaps correlating the epithelial damage with a mechanism for developing BO lesions. Many immunomodulatory medications and treatments have been studied for effectiveness for the treatment of chronic lung allograft dysfunction. New drugs, which more precisely target the immune system, are being developed and tested. Further study is required, but recent advances have improved our understanding of the pathogenesis and potential intervention for this common and deadly complication of lung transplantation.Keywords: lung transplant, bronchiolitis obliterans syndrome, rejection. (shrink)

Chad A Witt, Ramsey R Hachem Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, Saint Louis, MO, USA: The role of donor-specific antibodies to human leukocyte antigens and the burden of antibody-mediated rejection in lung transplantation remain enigmatic. Over the past several years, evidence has been emerging that humoral immunity plays an important role in the development of both acute and chronic lung allograft dysfunction. Multiple case reports and case series have identified (...) lung allograft recipients with clinical findings consistent with acute AMR. However, there is currently no widely accepted definition for AMR in lung transplantation, and this has been a significant barrier to furthering our understanding of this form of rejection. Nonetheless, the development of DSA after transplantation has consistently been identified as an independent risk factor for persistent and high-grade acute cellular rejection and CLAD. This has raised the possibility that chronic AMR may be a distinct phenotype of CLAD although evidence supporting this paradigm is still lacking. Additionally, antibodies to lung-restricted self-antigens have been associated with primary graft dysfunction early and the development of CLAD late after transplantation, and emerging evidence underscores significant interactions between autoimmunity and alloimmunity after transplantation. There is currently an active International Society for Heart and Lung Transplantation working group that is developing an operational definition for AMR in lung transplantation. This will be critical to improve our understanding of this form of rejection and conduct clinical trials to identify optimal treatment strategies. This review will summarize the literature on DSA and AMR in lung transplantation and discuss the impact of antibodies to self-antigens on lung allograft dysfunction. Keywords: antibody-mediated rejection, donor-specific antibodies, lung transplantation. (shrink)