The pulmonary alveoli form a habitat for alveolar macrophages (AM) and the lung microbiota. These two constituents impact on each other in addition to shaping and responding to the local microenvironmental conditions. Lung transplant recipients experience different inflammatory states influenced by tissue injury and repair, the response to the allograft, potential episodes of infection and the applied immunosuppressive and antibiotic therapies. During post-transplant follow-up, lung transplant recipients undergo routine endoscopy examinations with harvest of bronchoalveolar lavage fluid that provides a unique opportunity to build up a picture of the microenvironmental conditions in the lower airways.
We believe that a precise characterization of AM activation profile and lung microbiota load and composition will provide a valuable tool to define lower airways microenvironmental conditions and help discriminate between normal graft survival and chronic lung allograft dysfunction (CLAD). We aim to identify the factors that initiate changes in AM activation profiles and microbiota composition, as well as defining cause-effect relationships, will contribute by increasing our understanding of the mechanisms implicated in CLAD, refining the classification of this heterogenous condition, and thereby opening new avenues for targeted therapeutic intervention.