Differential expression of keratin 19 in normal human epithelial tissues revealed by monospecific monoclonal antibodies

Abstract

Three monospecific monoclonal antibodies (BA16, BA17 and A53-B/A2) recognizing different epitopes of the human keratin 19 were used to determine tissue distribution of this 40 kDa keratin polypeptide. Immunohistochemical methods revealed four different staining patterns among normal human epithelial tissues: firstly, complete negativity of the epidermis, sebaceous glands, hepatocytes and other tissues; secondly, homogeneous positivity as seen for example in the gall bladder and urinary bladder epithelium, endometrium and many other epithelia; thirdly, a mosaic of positive and negative cells among mammary gland luminal cells, prostate epithelia and some other epithelia and fourthly, a more complex heterogeneous pattern found in non-keratinizing squamous epithelia and hair follicles with generally the basal layer being the most strongly or sometimes exclusively stained. The pattern seen in non-keratinizing squamous epithelia varied considerably according to the fixation method and the antibody used as well as among different donors and in different areas of the same organ. The other three staining patterns were on the other hand nearly identical with all three antibodies on both frozen sections and sections of methacarn-fixed paraffin-embedded tissues. Our results provide evidence for differential expression of the human keratin 19 at the single cell level, an observation which could be exploited in the study of epithelial differentiation and pathology.

Expression of keratin K14 in the epidermis and hair follicle: insights into complex programs of differentiation.

“…However, the ORS differs from the epidermis in that it expresses Kt, K16, K17, and K19 (Bartek et al, 1986;Stark et al, 1987;Heid et al, 1988a;Moll et al, 1988). Moreover, although K1 and KI0 expression is high in the differentiating cells of the epidermis, their expression is extremely low in the ORS (Moll et al, 1988).…”

Different proliferative activity of the glandular and myoepithelial lineages in benign proliferative and early malignant breast diseases

“…1 In tissue sections, these cells can be discriminated by their localization and by the expression of simple type I keratins (CK8/18/19) and smooth muscle actin, respectively. [2][3][4] This two-cell paradigm has shaped successfully our understanding of pathological processes in the human breast over many decades.…”

The Type I Keratin 19 Possesses Distinct and Context-dependent Assembly Properties

“…Michel et al (20) recently extended the original findings of Stasiak et al (10) in showing that a fraction of the K19-expressing basal cells in mouse skin are thymidine label-retaining cells, an operational criteria for stem cell character. This K19-positive subpopulation of cells localizes to the deep portion of rete ridges in the epidermis of glabrous human skin and the bulge portion of hair follicles in hairy skin (10,20,65). Interestingly, a subset of "K14-low," less differentiated basal cells in the outermost "basal" layer of the hair follicle outer root sheath has been described by one of us (66), and these cells have been postulated to serve as progenitors for both the hair follicle outer root sheath and the epidermis.…”

“…Expression of K19 occurs in a number of epithelial settings and frequently correlates with a phenomenon of "plasticity" in epithelial cell fate or function (10,65). In contrast to many of the keratin genes expressed in the epidermis (2, 4, 5), mutations that affect the primary sequence and function of K19 have not yet been discovered in the human population.…”