[Graft immunity in lung transplantation]

Lung transplantation is an effective treatment for end-stage respiratory failure, however immunological mismatch poses a major threat to graft function.

An inflammatory process within the lung is initiated at the time of brain death of the donor which, even in the absence of rejection or infection, persists in the recipient after transplantation. Although immuno-suppressive therapy is able to control the cellular immune response, alveolar macrophages remain in an activated state and interactions between T cells and epithelial cells continue. Acute rejection is triggered by T cell activation with an amplification of the inflammatory process associated with mononuclear cells infiltration. The major complication of pulmonary transplantation is bronchiolitis obliterans, a pan-bronchitic process due in part to a chronic rejection process arising from the interactions between epithelial and immune cells. This immune process results in progressive tissue remodelling. Viral infections may influence pulmonary transplantation by interacting directly with the immune system; infections due to cytomegalovirus and common respiratory viruses may play a role in the long term decline of graft pulmonary function.

Concepts in lung transplantation immunology will evolve in forth-coming years as induction of microchimerism in the recipient is developed and/or organs from genetically modified porcine donors become available.

Improvements in immunosuppressive regimens are needed to reduce the risk of bronchiolitis obliterans in the transplanted lung.