Table 2.

Characteristic expression patterns of typical keratins in selected human normal epithelial tissues

	Keratins of simple epithelia			Keratins of stratified epithelia
Type II keratins:	K8	K7		K5		K6		K1	K2	K4
Type I keratins:	K18	K19	K10	K14	K15	K16	K17	K10	K9	K13
Parenchymatous epitheliaa	All cells
Ductal epithelia of parenchymatous organsb	All cells	K7 and K19 in all cells		Sparse cells			Sparse cells			K4 heterogeneously in pancreatic ducts
Gastrointestinal epithelia	All cells	K19 in all cells	Gastric foveolar epithelium, intestinal epitheliumc							K4 heterogeneously in luminal cells; K13 in sparse luminal cells
Respiratory epithelium	Predominantly luminal cells	K7 in luminal cells; K19 in all cells		Predominantly basal cells		K6 in basal cells	Predominantly basal cells
Urothelium	All cells	K7 and K19 in all cells	Luminal (umbrella) cells	Basal cells			Few basal cells			K13 in all basal and intermediate cells
Non-keratinizing stratified squamous epithelia	Some basal cells	K19 in many basal cells		Basal cell layer (predominantly)	Basal cells layer	Suprabasal compartment		At some sites focal expression in suprabasal cells		Suprabasal compartment
Epidermis				Predominantly basal cell layer	Basal cell layer			Suprabasal compartment	K2 in upper spinous and granular layer; K9 in palmoplantar epidermisd

Not included are the corneal keratins K3/K12, the gingival/hard palate keratin K76, the eccrine sweat gland-specific keratin K77, and the hair follicle-specific epithelial and hair keratins (for keratin expression in eccrine sweat glands and in the hair follicle, see the schematic drawings in Figs. 5 and 6)

^aIncluding hepatocytes, acinar cells of pancreas, proximal tubular cells of kidney

^bBile ducts, pancreatic ducts, renal collecting ducts

^cMost villus- and surface-lining cells; scattered cells in crypts

^dHeterogeneous expression in the suprabasal compartment