Table 1—

Alveolar epithelial type I (ATI) cell-specific and -associated proteins in normal adult lung

	Method^#	Location in ATI cells	Expression in other cell types^¶	[Refs.]
Group I. ATI-cell-specific
RTI₄₀/TIα protein	IEM	Apical plasma membrane	None	26–28
HTI₅₆	IEM	Apical plasma membrane	None	29
Group II. ATI-cell-selective
Caveolin-1/-2	IEM	Microvesicles	Endothelial cells, fibroblasts, smooth muscle cells, bronchial epithelial cells	30, 31
Na⁺/K⁺-ATPase α₂-isoform	IF, IEM	Basolateral membrane		32
Aquaporin 5	IEM	Apical plasma membrane	Bronchial epithelial cells	33
Cytochrome P₄₅₀ 2B1	IEM	Cytoplasm	Bronchial epithelial cells	34
Carboxypeptidase M	IHC	Apical plasma membrane	Alveolar macrophages	35
Group III. ATI-cell-selective/-associated
ICAM-1	IEM	Apical plasma membrane	Alveolar macrophages, bronchial epithelial cells, endothelial cells, ATII cells?	36–38
Connexin 43	IF	Cell membrane, cytoplasm	ATII cells	39
P-glycoprotein	IF	Apical plasma membrane	Smooth muscle cells, bronchial epithelium, ATII cells?	40
RAGE	IEM	Basal membrane	Some endothelial cells of larger blood vessels, ATII cells (mRNA)	41–43
PAI-1	IF	Apical plasma membrane	ATII cells?	44
P2X4 purinoceptor	IF	Plasma membrane	ATII cells?	44
CDKN2B	IF	Perinuclear	ATII cells?	44
ATB⁰⁺	IF	Apical membrane	Ciliated cells, ATII cells?	45
Cytochrome P₄₅₀ 1A1	ISH		Bronchiolar epithelium, ATII cells	46
Eotaxin	ISH		Airway epithelium, macrophages, lymphocytes, endothelial cells	47
GGT	IEM, IF	Apical plasma membrane	Clara cells, ATII cells	48, 49
IGFR-2	IHC	Apical plasma membrane		50