Table 1.

Pathological A‐grade classification of acute lung rejection

Grade	Meaning	Appearance
A0	None	No significant abnormality in lung parenchyma
A1	Minimal	Inconspicuous small mononuclear perivascular infiltrate
A2	Mild	More frequent perivascular infiltrates
A3	Moderate	Dense perivascular infiltrates, extension into interstitial and alveolar space, can involve endothelialitis
A4	Severe	Diffuse perivascular, interstitial, and airspace infiltrates with alveolar pneumocyte damage, potential parenchyma necrosis, infarction, or necrotizing vasculitis