The Role of Epithelial Damage in the Pulmonary Immune Response.

Pulmonary epithelial cells are widely considered to be the first line of defence in the lung and are responsible for coordinating the innate immune response to injury and subsequent repair. Consequently, epithelial cells communicate with multiple cell types including immune cells and fibroblasts to promote acute inflammation and normal wound healing in response to damage. However, aberrant epithelial cell death and damage are hallmarks of pulmonary disease, with necrotic cell death and cellular senescence contributing to disease pathogenesis in numerous respiratory diseases such as idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and coronavirus disease (COVID)-19.

Pathophysiology and classification of primary graft dysfunction after lung transplantation.

The term primary graft dysfunction (PGD) incorporates a continuum of disease severity from moderate to severe acute lung injury (ALI) within 72 h of lung transplantation. It represents the most significant obstacle to achieving good early post-transplant outcomes, but is also associated with increased incidence of bronchiolitis obliterans syndrome (BOS) subsequently. PGD is characterised histologically by diffuse alveolar damage, but is graded on clinical grounds with a combination of PaO2/FiO2 (P/F) and the presence of radiographic infiltrates, with 0 being absence of disease and 3 being severe PGD.