TABLE 1.

PATHOLOGIC GRADING OF LUNG REJECTION

Category	Grade	Meaning	Appearance
A: acute rejection	0	None	Normal lung parenchyma
	1	Minimal	Inconspicuous small mononuclear perivascular infiltrates
	2	Mild	More frequent, more obvious, perivascular infiltrates, eosinophils may be present
	3	Moderate	Dense perivascular infiltrates, extension into interstitial space, can involve endothelialitis, eosinophils, and neutrophils
	4	Severe	Diffuse perivascular, interstitial, and air-space infiltrates with lung injury. Neutrophils may be present.
B: airway inflammation	0	None	No evidence of bronchiolar inflammation
	1R	Low grade	Infrequent, scattered or single layer mononuclear cells in bronchiolar submucosa
	2R	High grade	Larger infiltrates of larger and activated lymphocytes in bronchiolar submucosa. Can involve eosinophils and plasmacytoid cells.
	X	Ungradable	No bronchiolar tissue available
C: Chronic airway rejection – obliterative bronchiolitis	0	Absent	If present describes intraluminal airway obliteration with fibrous connective tissue
	1	Present
D: Chronic vascular rejection – accelerated graft vascular sclerosis		Not graded	Fibrointimal thickening of arteries and poorly cellular hyaline sclerosis of veins. Usually requires open lung biopsy for diagnosis.