Update on pathology of antibody-mediated rejection in the lung allograft

The determination of antibody-mediated rejection (AMR) in the pulmonary allograft remains a diagnostic challenge. Herein, we review the pathologic findings from recent studies, including the International Society of Heart and Lung Transplantation (ISHLT) summary statement on pulmonary AMR and preliminary data from the Banff allograft pathology study on AMR in lung transplant patients. Some pathologic findings, including acute lung injury and neutrophilic capillary infiltration, are likely to be associated with pulmonary AMR but do not appear to be specific pathologic markers. The ISHLT statement on pulmonary AMR lists numerous pathologic findings that may be associated with donor-specific antibodies (DSAs). Other recent studies, including the Banff study on pulmonary AMR, have found correlations between clinical AMR, defined in part by the presence of DSAs, and nonspecific acute lung injury and capillary neutrophils with or without C4d deposition. At this time, the diagnosis of lung transplant AMR requires multidisciplinary coordination and is ultimately determined by the managing clinician. In the full clinical context, including knowledge of serologic data for the presence or absence of DSAs, pathologic interpretation may provide valuable information that can guide therapy and support the clinical diagnosis.