Final answer:
Chronic lung transplant rejection involves the recipient's immune response against the transplanted tissue, which can lead to bronchiolitis obliterans, hence deteriorating lung function despite matching donor tissues and immunosuppression.
Step-by-step explanation:
Chronic rejection of lung transplantation results in a long-term immune response against the transplanted lung tissue. The recipient's immune system recognizes the transplanted lung tissue as foreign due to genetic differences, particularly in the MHC (HLA) genes, leading to an immune attack on the lung tissue.
Despite efforts to match donor and recipient tissues and the use of immunosuppressive drugs, rejection can still occur. Chronic rejection of lung transplants can manifest as a condition known as bronchiolitis obliterans, characterized by inflammation and fibrosis of the small airways, ultimately leading to lung function deterioration over time.