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

Structural changes in the gastric foveolar epithelium in Helicobacter pylori-positive gastritis revealed by keratin immunohistochemistry

To clarify structural changes in the gastric foveolar epithelium in Helicobacter pylori (Hp)-positive gastritis, the expression rates of keratins 8, 18, 19, and 20 were assessed immunohistochemically in normal tissue and chronic gastritis. In normal tissue, keratin 8 was found in 100% of the cells. Staining for keratins 18 and 19 was abundantly positive. Keratin 20 was not expressed in the deep foveolae, but present in the upper foveolae and on the tips. No differences were found between the antrum and the body. In chronic gastritis, both Hp-positive and -negative, keratins 8, 18, and 19 were expressed comparably to normal tissue. Keratin 20 expression in the antrum was significantly lower in Hp-positive compared with Hp-negative gastritis (P < .05) and normal tissue (P < .05). In the body, staining for keratin 20 did not differ significantly between all groups. The difference in keratin 20 expression between the antrum and the body in Hp-positive gastritis was significant (P < .05). After successful eradication, staining for keratin 20 in the antrum normalized within 6 months (P < .05). These findings indicate structural changes in the gastric foveolar epithelium in Hp-positive gastritis. They predominantly include the antral region and show full reversibility after eradication.

Fibroblasts can modulate the phenotype of malignant epithelial cells in vitro

An organotypic, tridimensional cell culture, also called a raft system, was used to study the influence of fibroblasts on epithelial carcinogenesis in a cell line derived from laryngeal squamous cell carcinoma and harboring a mutated p53. Differences between the effects of normal fibroblasts and those of tumor-derived fibroblasts were compared by means of fibroblasts taken from the normal skin and from the tumor of a cancer patient and cultivated with epithelial carcinoma cells in an organotypic culture. To study cell contact-mediated changes, the fibroblasts were either simply embedded in collagen matrix or additionally brought into direct contact with epithelial cells. Control epithelial cells were cultivated without any fibroblasts in an organotypic model. A protein panel [p53, p21, PCNA, bcl-2, Ki67, total cytokeratin (CK), CK 8, CK 10, CK 17, CK 18, CK 19, vimentin] involved in cell cycling and epithelial differentiation was assessed immunocytochemically in all organotypic cultures with fibroblasts, in tumor cells cultivated as a monolayer, and in the original tumor sample. The most dysplastic phenotype was obtained when tumor-derived fibroblasts were used in direct contact with epithelial cells, whereas the most benign phenotype was seen when skin fibroblasts had no contact with them. The intensive staining seen for p53 can be explained by p53 mutations also reflecting the weak expression of p21 and abundant expression of PCNA. The intensive Ki67 staining seen in all sections paralleled that of PCNA and marked active cellular proliferation. The CK staining pattern seen in cultured epithelia toward embryonic CKs, CK 8 and CK 18, suggested a simple epithelial phenotype. CK 19 was found only in the epithelium where no direct contacts had occurred. Vimentin expression increased when the raft epithelium was shifting toward a more benign phenotype. The results stress the importance of the origin of fibroblasts as well as the role of direct cellular contacts in modifying the epithelial phenotype even when the epithelial cells are malignant.

Effect of snuff on cytokeratin expression in oral vestibular sulcus epithelium

Differences in the expression of cytokeratins (CK) in specimens obtained from snuff-affected oral epithelium of the maxillary vestibular sulcus and clinically normal sulcular epithelium were studied by indirect immunofluorescence staining with a panel of monoclonal antibodies (MAbs). CK 14, a marker of stratified squamous epithelium was not seen expressed in 3/11 of the snuff user's specimens. Terminal differentiation markers, typical of cornified epithelia (CK 1, 9, 10 and 11), were detected suprabasally in the snuff user's keratosis but not in the normal control epithelium. The use of snuff seemed to change the CK staining pattern of the mucosa so that it resembles more that of a cornified type of epithelium. Simple epithelial-type CK were included in the study in order to establish the CK profile of the snuff-induced keratosis, for comparison with normal and dysplastic lesions. MAb to CK 7 and 19 showed reactivity in the basal cells and suprabasally whereas the monospecific MAb anti-CK 7 showed suprabasal staining both in the control and affected epithelia. By using MAbs, we found no immunoreactivity against CK 18 either in normal or affected epithelia, whereas we found suprabasal reaction (5/11) against CK 8 in the snuff user's epithelia. The two MAbs demonstrating the expression of CK 19, normally confined to the basal cells of the stratified squamous epithelium, showed variable patterns of expression both in basal cells and suprabasally in the snuff lesions. The results show that use of oral snuff causes some alterations in the CK expression pattern of the affected epithelium. Whether the alterations are indicative of a premalignant change is, however, uncertain. The results encourage further studies on the subject.

The distribution and origin of keratin 20-containing taste buds in rat and human

Sections of tissues containing lingual and extra-lingual taste buds were evaluated with monoclonal antibodies against cytokeratins. In the caudal third of the rat's tongue, keratin 20 immunoreactivity was restricted to taste buds, whereas keratins 7, 8, 18, and 19 were expressed in vallate and foliate taste buds and in cells of salivary ducts that merge with these taste epithelia. Hence, antibodies against keratin 20 most clearly distinguished differentiated taste cells from all other cells. In rat epiglottis, taste buds and isolated bipolar cells were keratin-20-positive. In rat nasopalatine papilla and palate, antibodies against keratin 20 identified Merkel cells, none of which was near to the keratin-20-negative taste buds. Nor were Merkel cells present at epiglottal taste buds or the keratin-20-negative fungiform taste buds or elsewhere in rat tongue. Hence, Merkel cells make no contribution to rat fungiform, epiglottal, nasopalatine, or palatal taste buds. Human and rat keratin-20-positive tissues are reported to be endodermal derivatives with the exception of Merkel cells and luminal urothelial cells. In rats the distribution of keratin-20-positive taste buds was in full agreement with the classical view that the posterior third of the tongue is derived from endoderm (keratin-20-positive taste buds), whereas the anterior two-thirds of the tongue is derived from stomadeal ectoderm (keratin-20-negative taste buds). The equally intense keratin 20 immunoreactivity of human fungiform and vallate taste buds violates this traditional rostro-caudal segregation and suggests that endodermally derived tissues may be present in the tip of the human tongue.

A limited role for retinoic acid and retinoic acid receptors RAR alpha and RAR beta in regulating keratin 19 expression and keratinization in oral and epidermal keratinocytes

Different types of stratified squamous epithelia-for example, the "orthokeratinized" epidermis, the "parakeratinized" gingiva, and the "nonkeratinized" oral lining mucosal epithelia-are formed by intrinsically distinct keratinocyte subtypes. These subtypes exhibit characteristic patterns of keratin protein expression in vivo and in culture. Keratin 19 is an informative subtype-specific marker because the basal cells of only nonkeratinizing epithelia express K19 in vivo and in culture. Epidermal keratinocytes normally do not express K19, but can be induced to do so in culture by retinoic acid (RA). Keratinocyte subtypes express the retinoic acid receptor (RAR) beta at levels roughly correlated with their level of K19 expression in culture and their potential for forming a nonkeratinized epithelium in vivo. We tested the hypothesis that the level of RAR beta expressed by a keratinocyte determines its K19 expression and its form of suprabasal differentiation. Normal human epidermal and gingival keratinocytes stably overexpressing either RAR beta or RAR alpha were generated by defective retroviral transduction. Overexpression of either receptor enhanced the RA inducibility of K19 in conventional culture, in that the proportion of the transductants becoming K19+ in response to RA was markedly increased compared with controls. The pattern of differentiation of the epithelium formed in organotypic culture, assessed by basal K19 and suprabasal K1, K4, and filaggrin expression, however, was unaltered by RAR overexpression. Thus, the susceptibility of keratinocytes to regulation of K19 expression by retinoids is conditional, and levels of neither RAR beta nor RAR alpha are limiting to the intrinsic mechanism that specifies alternate differentiation pathways for stratified squamous epithelia.

Keratin 19 as a biochemical marker of skin stem cells in vivo and in vitro: keratin 19 expressing cells are differentially localized in function of anatomic sites, and their number varies with donor age and culture stage

This study was undertaken to evaluate keratin 19 (K19) as a biochemical marker for skin stem cells in order to address some long standing questions concerning these cells in the field of cutaneous biology. We first used the well-established mouse model enabling us to identify skin stem cells as [3H]thymidine-label-retaining cells. A site directed antibody was raised against a synthetic peptide of K19. It reacted specifically with a 40 kDa protein (K19) on immunoblotting. It labelled the bulge area of the outer root sheath on mouse skin by immunohistochemistry. Double-labelling revealed that K19-positive-cells were also [3H]thymidine-label-retaining cells, suggesting that K19 is a marker for skin stem cells of hair follicles. K19-expression was then used to investigate the variation in mouse and human skin stem cells as a function of body site, donor age and culture time. K19 was expressed in the hair follicle and absent from the interfollicular epidermis at hairy sites (except for some K18 coexpressing Merkel cells). In contrast, at glabrous sites, K19-positive-cells were in deep epidermal rete ridges. K19 expressing cells also contained high levels of alpha 3 beta 1 integrin. The proportion of K19-positive-cells was greater in newborn than older foreskins. This correlated with keratinocyte culture lifespan variation with donor age. Moreover, it could explain clinical observations that children heal faster than adults. In conclusion, K19 expression in skin provides an additional tool to allow further characterization of skin stem cells under normal and pathological conditions in situ and in vitro.

Cytokeratin expression patterns by one- and two-dimensional electrophoresis in pars flaccida cholesteatoma and pars tensa cholesteatoma

Expression patterns of cytokeratins (CKs) in normal skin, in pars flaccida type cholesteatoma (PFTC), and in pars tensa type cholesteatoma (PTTC) were examined by means of one- and two-dimensional electrophoretic techniques. Both CKs 14 and 5 pair (CKs 14/5) and CKs 10/1 were found in all materials. Neither CKs 16/6 nor 19 was found in the skin. CKs 16/6 and 19 were both found in 3 out of 5 PFTCs, only CKs 16/6 in 1 out of 5 and neither CKs 16/6 nor 19 in 1 out of 5. CKs 16/6 and 19 were both found in 1 out of 3 PTTCs, only CKs 16/6 in 1 out of 3 and neither CKs 16/6 nor 19 in 1 out of 3. There was no significant difference in the CKs expression patterns between PFTC and PTTC. The expression of CKs 16/6 and 19 suggested that their matrix epithelia were hyperproliferative. However, not all of the cholesteatomas were always hyperproliferative. Patterns of the terminal differentiation of CKs 1, 5, 10 and 14 in the PFTC or the PTTC were basically the same as those in the skin. In the cholesteatoma, eack CK gradually diminished in molecular weight in the cornified layer and debris. Desmosomal proteins were abundant in skin but not in cholesteatomas.

Keratin 18 is associated with a subset of older taste cells in the rat

All or nearly all intragemmal (elongated) cells of rat taste buds were immunopositive for keratins 7, 8, and 19. In contrast, keratin 18 was detected in 19 +/- 5 cells per taste bud (mean +/- sd), or about 25% of the intragemmal cells. During taste bud development keratins 7, 8, and 19 were evident initially in polygonal cells and later in elongated taste cells. Keratin 8 appeared in vallate taste cells at P0 (postnatal day 0), followed by keratins 7 and 19 at P1, and keratin 18 at P2-P3. Keratin 18 was always limited to elongated cells. The assemblage of elongated taste cells comprising a taste bud began with a single elongated cell, rather than with the synchronous elongation of a cluster of cells. Developmental errors were observed at P2-P3, e.g., some vallate taste cells had a misoriented axis. In order to study the pace of keratin differentiation during cell turnover we injected bromodeoxyuridine (BrdU) into adult rats to monitor taste cell age. Keratin-19-positive intragemmal cells differentiated within 1 day. In contrast, keratin 18 was first detected in cells aged 3 days. Hence, both in taste cell development and replacement, keratin 18 was restricted to the older cells; it was the last taste cell keratin to become expressed during differentiation.

Epitope mapping of monoclonal antibodies to keratin 19 using keratin fragments, synthetic peptides and phage peptide libraries

To generate tools for monitoring processing and folding in keratin intermediate filaments, a group of monoclonal antibodies reacting with the intermediate filament protein keratin 19 were studied using different approaches to define the structure and localization of their epitopes. The binding pattern to bacterially expressed human keratin 19 fragments allowed the definition of minimal amino acid sequences required for antibody binding. The screening of overlapping 15-residue peptides confirmed and further specified the epitope locations for a subset of the tested antibodies. In addition, the epitope of an antibody with apparent species-restricted specificity (LE64) was revealed by isolating and characterizing a full-length keratin 19 clone from a PtK2 cDNA library. Taken together with species cross-reactivity of individual antibodies and sequence information obtained by probing a phage display library, specific amino acid residues could be highlighted as likely to be involved in the antibody binding.

Keratins as markers of differentiated taste cells of the rat

Cytokeratins in taste buds were immunocytochemically evaluated with monoclonal antibodies. In each of six different epithelial sites in the rat oral cavity, intragemmal cells of taste buds were immunoreactive for keratin polypeptides 8, 18, and 19, as well as for keratin 7, which has not been previously reported in taste buds. Keratin-18-like immunoreactivity was present in fewer than half of the intragemmal cells, whereas all intragemmal cells were immunopositive for keratins 7, 8, and 19. Apart from some salivary duct cells, no other cells in the tongue were immunoreactive for any of these four keratins. Morphological and immunocytochemical profiles indicate that taste buds are islets of simple epithelium embedded in an expanse of stratified squamous epithelium. These simple epithelial cells and their keratins are nerve-dependent, since denervation eliminated all four keratins and replaced elongated taste cells of the vallate papilla with stratified squamous epithelium. We conclude that antibodies against keratins 7, 8, or 19 are useful markers for intragemmal cells in studies of taste bud development, degeneration, regeneration, turnover and tissue culture.

Different organization of intermediate filaments in columnar cells of rat large intestinal mucosa as revealed by confocal laser scanning microscopy and quick-freezing and deep-etching method

The relationship between cell differentiation and ultrastructural changes of intermediate filaments (IF) was studied in columnar cells of large intestinal mucosa of rats by confocal laser scanning microscopy and quick-freezing and deep-etching method. A feature of the IF in immature columnar cells was minibundle formation with prominent branching, which organized the meshwork structures. The minibundles, which appeared to be formed by the attachment of two or more IF in side-to-side fashion, were loosely distributed throughout the cytoplasm. In contrast, in mature columnar cells, the IF were densely distributed under the terminal web in the cytoplasm and beneath the upper part of the lateral membrane regions, whereas the other areas of the cytoplasm contained only a small number of IF. Minibundle formation was not observed, and the branching was rarely identified. The changes in the distribution and density of IF, which are expressed in specific areas of mature columnar cells, apparently represent a characteristic of intracellular differentiation. It is suggested that the dissociation of minibundled IF, which was often observed in the immature columnar cells, is an important step in the acquisition of functional polarity in cells of this type.

Expression of cytokeratin mRNAs in normal human esophageal epithelium

BACKGROUND

The cytokeratin (CK) pattern is accepted to be characteristic of a given epithelial cell or tissue. Specific changes in the CK pattern or in the expression of individual CKs may be characteristic in the early development of particular epithelial pathologies. Up to now no systematic hybridohistochemical study on the expression of CKs in normal human esophageal epithelium has been performed. Nevertheless, this knowledge may be of great importance for further research concerning the understanding of the structure and differentiation of normal esophageal epithelium and of the development of non-neoplastic and neoplastic esophageal malignancies. Therefore, we investigated the expression and distribution of nine different CK mRNAs throughout the normal human esophageal mucosa.

METHODS

A non-radioactive in situ hydridization protocol was used to study the expression of CK mRNAs in fixed and paraffin-embedded human esophageal mucosa. Digoxigenin-labelled cRNA probes were produced by in vitro transcription of cDNA clones, coding for human CKs.

RESULTS

In situ hybridization and immunodetection of the hybrids revealed a distinct but different distribution pattern for each specific CK mRNA. The described signal pattern was consistently found at all levels of the esophagus. We observed differences in the expression of some CK mRNAs between the interpapillar and papillar compartment of the esophageal epithelium. Mainly in the papillar regions some mRNAs are already expressed in more basally located cells in comparison with the interpapillar regions. Our results substantiate the hypothesis concerning the formation of papillae in the esophageal mucosa. We have also described some observations on the expression of CK mRNAs in fortuitous sections through excretory ducts of esophageal submucosal glands.

CONCLUSIONS

The distinct, characteristic, and reproducible distribution pattern observed for each specific CK mRNA indicates that the expression of the genes encoding CKs in the esophageal epithelium as well depends on the cell proliferation, on vertical cell migration and differentiation, and on detachment from the basal lamina. The results presented should be considered as complementary to the already existing immunohistochemical results concerning the distribution of esophageal CK proteins.

Keratin staining pattern in clinically normal and diseased oral mucosa of lichen planus patients

The keratin pattern in oral epithelia is related to the type of terminal differentiation observed morphologically (keratinization/nonkeratinization) and to the presence or absence of epithelial dysplasia. Furthermore, it has been suggested recently that inflammatory phenomena influence the keratin expression in human gingiva. The aim of the present study was to describe the keratin pattern in oral lichen planus (OLP) lesions, which are well known to be characterized by hyperkeratinization and severe inflammatory changes, in order to elucidate the role of inflammation in keratin expression of oral epithelia. Tissue sections were stained with antikeratin antibodies directed to groups of keratins (AE1 and AE2) and to single keratin proteins (Nos. 5, 8, 13, and 19). The keratin pattern in OLP lesions differed in some respects from that of leukoplakias and frictional keratoses as characterized in previous studies. No consistent patterns for use in a diagnostic context were found. However, the changes in OLP lesions did not mimic those previously described in inflamed gingival specimens and in oral epithelial dysplasias. Thus, the results encourage further studies on the potential diagnostic use of keratin expression in premalignant oral lesions. Furthermore, the study suggests that the inflammatory reaction seen in OLP lesions does not influence keratin expression in a way comparable with the suggested influence of inflammation in gingival specimens.

Cytokeratin 18 is an M-cell marker in porcine Peyer's patches

The intermediate filaments of the dome epithelium of porcine Peyer's patches were studied by immunohistochemistry. The labelling patterns of monospecific antibodies directed against cytokeratins 8, 18 and 19 differed considerably. About 40% of the dome epithelial cells were intensely labelled by three different anti-cytokeratin 18 antibodies, indicating that large amounts of cytokeratin 18 are present in these cells. In order to verify that these cytokeratin-18-immunoreactive cells were M-cells, uptake studies using fluorescein-labelled yeast particles were performed. Numerous yeast particles were found exclusively in dome epithelial cells that were highly positive for cytokeratin 18, thus representing M-cells. In contrast, the content of cytokeratin 19 in M-cells was lower than that in neighbouring enterocytes. The labelling intensity of cytokeratin 8 did not differ between M-cells and enterocytes. In addition, the absence of vimentin and desmin from the dome epithelium of porcine Peyer's patches was demonstrated. The results show (1) that porcine M-cells differ from enterocytes in the composition of their cytoskeleton, (2) that cytokeratin 18 is a useful marker for detecting porcine M-cells and (3) that this marker directly correlates with M-cell function.

Cytokeratin patterns of normal middle ear epithelia in humans, cats, and chinchillas

We describe the cytokeratin patterns of epithelia from the tympanic orifice, tympanic cavity, and mastoid cavity of humans, cats, and chinchillas, and compare these findings with those of tracheal epithelium and external canal epidermis. Our findings are as follows: 1) middle ear epithelium from all locations demonstrates some type of cytokeratin staining, 2) broad-spectrum cytokeratin antibodies stain epithelia of middle ear cleft, tracheal epithelium, and external canal epidermis in all species, 3) specific cytokeratin antibodies reveal species-related differences in middle ear and tracheal epithelia, 4) middle ear and tracheal epithelia usually have the same pattern, and 5) none of the monospecific cytokeratin antibodies have a positive reaction with external canal epidermis. These findings suggest that the cytokeratin patterns of middle ear epithelium are useful in studying the hyperplastic and metaplastic changes in otitis media; however, caution must be exercised when making interspecies comparisons.

Ductal adenoma of the breast. An immunohistochemical study of five cases

The immunohistochemical features of 5 ductal adenomas of the breast were investigated. The tumours were composed by tubular glands lined by cells with both luminal and basal/myoepithelial immunophenotypes. Tubules were encircled by an intact basement membrane as demonstrated by staining for laminin and type IV collagen. Areas of dense fibrosis, a usual finding in these lesions, stained for fibronectin, type III collagen and contained vimentin and actin positive spindle cells, consistent with myofibroblasts. These observations confirm a double epithelial and myoepithelial differentiation in these lesions and seem to support the suggestion that ductal adenomas result from sclerosis of ductal papillomas.

Development of human fetal lung in organ culture compared with in utero ontogeny

In utero, at around 23 wk gestation, the progenitor epithelium of distal airway differentiates into type I and type II pneumatocytes. Human fetal lung organ cultures, as early as 12 wk gestation, have the competence to self-differentiate. Distal airway epithelial immunoreactivity to cytokeratins CK 7, 8, and 18 decreases with differentiation both in utero and in organ culture, whereas reactivity to epithelial membrane antigen remains constant in both. As distal airways dilate, the mean percentage airspace of fetal lungs in organ culture increases to 58%, equivalent to lung of gestation 26.0 +/- 7.3 wk. In organ culture, capillary blood vessels, visualized by vimentin immunoreactivity, remodel and more closely approximate the epithelium but without direct invasion. In utero, at 23 wk gestation, elastin appears as condensation around airways and forms a basis for secondary crests which, by 29 wk gestation, evolve into alveolar septae. In organ culture, no elastin is deposited, no secondary or alveolar crests form, and the lung retains a simple saccular structure. Differentiation of the terminal airway epithelium and mesodermal maturational events to facilitate gas exchange, such as capillary invasion or secondary-alveolar crest formation, are almost synchronous in human lung in utero but clearly dissociate in organ culture.

A panel of biomarkers of carcinogenesis of the upper aerodigestive tract as potential intermediate endpoints in chemoprevention trials

BACKGROUND

Patients with squamous cell carcinoma of the head and neck have a 10-30% risk of developing a second primary tumor. The concept of "field cancerization" assumes that the whole upper aerodigestive tract is affected and prone to malignant transformation. This study was undertaken to investigate the value of a panel of monoclonal antibodies to identify biomarkers in oral mucosa associated with cancer risk. Such biomarkers may be suitable candidates to serve as intermediate endpoints in cancer chemoprevention trials.

METHODS

As a model, the expression of antigens was assessed in cytologic preparations obtained from macroscopically normal oral mucosa of patients with tongue carcinoma and of controls. The panel consisted of antibodies against cytokeratin 8, 10, 13, and 19 and the monoclonal antibodies designated K931, K984, E48, Ki-67, and UM-A9.

RESULTS

Oral mucosa of cancer patients had a more than threefold increased expression of cytokeratin 19 as compared with controls (36.0 versus 11.3%; P < 0.01).

CONCLUSION

Cytokeratin 19 is a potential intermediate endpoint in head and neck cancer chemopreventive trials.

Immunohistochemistry with keratin monoclonal antibodies in canine tissues: urogenital tract, respiratory tract, (neuro-)endocrine tissues, choroid plexus and spinal cord

Twelve oligo- or monospecific monoclonal antibodies (MoAbs) directed against human keratin types were used in an immunohistochemical study of the canine male and female urogenital tract, the respiratory tract, the adrenal gland, the (para-)thyroid gland, the choroid plexus and the spinal cord. The keratin MoAbs showed differences in staining patterns in the various epithelial tissues and the diverse epithelial cells. The kidney was characterized by a complex keratin staining pattern and the canine urothelium showed regional differences in keratin staining. Also in the female genital tract different keratin staining patterns were observed. Testicular and adrenal gland cells did not react with any of the keratin MoAbs. The keratin staining patterns in the various canine tissues showed, in addition to similarities, also distinct differences when compared to the staining patterns in corresponding tissues of other species, e.g. of man. These staining dissimilarities indicate that the reactivity patterns of the keratin MoAbs with restricted keratin immunoreactivity can not be always extrapolated from one species to another. Nevertheless, MoAbs directed against human keratin proteins can apparently be used to differentiate between various types of canine epithelia or epithelial compartments.

Monoclonal antibody analysis of keratin expression in carcinomas of sweat glands

Characteristics of keratins of five carcinomas of sweat gland origin were immunohistochemically investigated with several antikeratin monoclonal antibodies with differing specificities. Specimens were obtained from two cases of mucinous carcinoma of the skin, two cases of classic type of eccrine adenocarcinoma, and a case of eccrine porocarcinoma. The tumor cells of mucinous carcinoma expressed only simple epithelial keratins. In a case of eccrine adenocarcinoma, simple epithelial keratin 19 was diffusely expressed. The expression of the other simple epithelial keratins was confined to the luminal cells, whereas the remaining tumor cells further expressed stratified epithelial keratins. Eccrine porocarcinoma and a second case of eccrine adenocarcinoma did not express simple epithelial keratins, although stratified epithelial keratins were diffusely expressed. These data suggest that carcinomas of sweat glands express various combinations of simple and stratified epithelial keratins. Development of additional data along these lines may help to further define their classification.

Co-localization of vimentin and cytokeratins in M-cells of rabbit gut-associated lymphoid tissue (GALT)

The occurrence of cytokeratins, vimentin, and desmin in the dome epithelia and adjacent non-dome epithelia in four locations of gut-associated lymphoid tissues (GALT) of adult and newborn rabbits (Peyer's patches, sacculus rotundus, caecal lymphoid patches and appendix) was studied with monoclonal antibodies, using the indirect immunoperoxidase technique. In all locations investigated in adult animals, antibodies specific for vimentin labelled (1) M-cells, which engulf intra-epithelial lymphocytes, (2) columnar epithelial cells at the base of the domes lacking an apparent contact with lymphocytes ("immature" M-cells), and (3) flat cells, which lie in the lamina propria under the dome epithelium, and which line the basal lamina with thin cytoplasmic processes. In newborn rabbits, columnar epithelial cells resembling the immature M-cells of adults were selectively stained with vimentin antibodies. In M-cells, the strongest immunoreactivity was present in the perinuclear region and close to the pocket membrane, whereas the most apical and most basal parts of the cytoplasm showed no vimentin-immunoreactivity. Enterocytes in the dome epithelium and in the non-dome epithelium were vimentin-negative. M-cells and enterocytes bound antibodies against cytokeratin peptides 18 and 19 in adult and newborn animals. Compared with enterocytes, M-cells showed less intense staining for cytokeratins. Dome epithelia and no-dome epithelia did not contain desmin-immunoreactive cells. The results suggest that vimentin is a sensitive marker for M-cells in rabbit GALT.

Immunohistochemistry with keratin and smooth muscle actin monoclonal antibodies in canine digestive tract and extramural glands

The canine digestive system and its extramural glands (parotid gland, liver, pancreas) were immunohistochemically studied using a panel of twelve monoclonal antibodies (MoAbs) specific for human keratin proteins and for alpha-smooth muscle actin. Various epithelial tissues and cells were characterized by different keratin staining patterns. So, the epithelial lining of the upper alimentary tract was characterized by staining with the MoAb 6B10, specific for keratin-type (K) 4, and the absence of staining with the MoAbs directed against K 8 and 18 (CAM 5.2 and RGE 53, DE-K18 respectively), whereas the lower alimentary tract epithelium was not labeled by 6B10, but stained by the latter MoAbs. In the salivary glands the luminal and basal cells of the adenomeres as well as the different ductal structures could be immunohistochemically differentiated. The duct epithelium in liver and pancreas showed next to keratin staining characteristics in common with hepatocytes and exocrine pancreatic cells, additional staining by several keratin MoAbs. The keratin staining patterns in the canine tissues showed, in addition to similarities also distinct discrepancies when compared to the staining patterns in corresponding human tissues. Myoepithelial cells in salivary and oesophageal glands could be differentiated from other basally located epithelial cells by their exclusive immunoreactivity for alpha-smooth muscle actin. Canine pancreatic endocrine cells were not labeled by any of the keratin MoAbs. It is concluded that immunohistochemistry with polypeptide specific MoAbs specific for human keratin-types can be used to differentiate between different types of canine epithelial tissues and epithelial cells in the digestive tract. As a result such reagents may find their application in developmental biology and pathology of this species.

Changes of expression of intermediate filament proteins during ontogenesis of eccrine sweat glands

The intermediate filament expression in fetal and adult human eccrine sweat glands was studied by immunoperoxidase microscopy performed on cryostat sections using monoclonal antibodies against various cytokeratins (CK), vimentin, and actin. In palmar skin of 14-week-old fetuses, the early dermal cords showed a primitive CK pattern similar to that of epidermal basal cells. From week 15 on (distal finger skin), inner cells of the proximal (ductal) portion of the glandular anlagen expressed CK 1/10/11 and 19 (markers of adult eccrine ductal luminal cells). In addition, CK 4 was expressed in ductal luminal cells mainly in the fetal period. In the distal portion of the sweat gland anlagen the increased or new expression of the simple-epithelium-type CK 7, 8, 18, and 19 was detected at week 15, indicating the onset of the secretory differentiation pathway. Two subsegments of the prospective secretory portion could be distinguished (elongated part and end bud). Interestingly, in fetuses, most secretory portion cells co-expressed vimentin in addition to CK. From week 22 on, peripheral cells of the secretory portion were stained for CK 17 and smooth-muscle-type actin, suggesting myoepithelial differentiation. In newborn and adult eccrine glands, secretory cells expressed mainly CK 7, 8, 18, and 19, whereas myoepithelial cells were conspicuous by their co-expression of certain CK (including CK 5 and 17), vimentin, and smooth-muscle-type actin and sometimes even glial filament protein (GFP), similar to myoepithelial cells of other glands. These results throw further light onto the complex processes of fetal development of eccrine sweat glands and their cellular diversification. The possible biologic significance of the differential CK expression in the various glandular cell types is discussed.

Intermediate filament protein profiles of human testicular non-seminomatous germ cell tumors: correlation of cytokeratin synthesis to cell differentiation

The patterns of cytoskeletal differentiation were studied in 20 testicular non-seminomatous germ cell tumors by immunohistochemistry, using diverse monoclonal antibodies specific for different intermediate filament (IF) proteins and for desmoplakin. Immunofluorescence and immunoperoxidase methods on both formalin-fixed and frozen tissues were applied, in some cases together with a gel electrophoretic analysis of IF proteins. The tumors examined included embryonal carcinoma (EC), endodermal sinus tumor (EST), choriocarcinoma and teratoma. Nine of the tumors were composed of only one histological type, the others showed mixed components. Cytokeratins 8 and 18 were identified in all these neoplasms, but their immunostaining was weak in ECs. Cytokeratin 19 was absent or very scarce in ECs, but strongly expressed in ESTs, choriocarcinomas and teratomas, thus allowing the identification of small EST and choriocarcinoma elements in ECs even when they were morphologically not obvious. Occasionally, some cells in ECs and ESTs also stained for cytokeratins 4 and/or 17, indicating potential for epithelial stratification. The majority of the germ cell tumors showed varied amounts of vimentin, often in co-existence with cytokeratins. Neurofilaments were demonstrated in scattered tumor cells in a single case of EST. In the teratomas studied, each type of tissue component present showed the expected IF protein. However, in many germ cell tumors some stromal cells and blood vessels contained, in addition to vimentin and desmin, also cytokeratins 8 and 18. This heterogeneity of the cytoskeletal profile of germ cell tumors is indicative of the varied differentiation potential inherent in these neoplasms.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of simple epithelial keratins 8 and 18 in epidermal neoplasia

A systematic study of keratin expression in epidermal lesions (six actinic keratoses, 10 Bowen's disease, seven squamous cell carcinomas) has been undertaken by using a large panel of monospecific monoclonal antibodies to individual keratins. Expression of differentiation-specific keratins was frequently delayed or lost from dysplastic regions. Novel expression of the embryonic, or simple epithelial, keratins 8 and 18 was widely observed in intradermal areas of poorly differentiated squamous cell carcinomas. In addition, the most proliferative of in situ malignancies (Bowen's disease) also contained small numbers of cells expressing simple epithelial keratins. These observations suggest that the expression of simple epithelial keratins may be of functional importance in malignancy of keratinocytes and could be related to tumor invasion and/or to changes in epithelial-mesenchymal interactions.

New monoclonal antibodies reacting with bile ducts: further insights into the pathogenesis of bile ductular proliferation in biliary diseases

We have produced a range of monoclonal antibodies which stain human intrahepatic bile ducts of different sizes. Amongst 26 monoclonal antibodies produced, five clones reacted specifically with bile ducts of different sizes, of which three have been maintained in culture and their viability following freezing and thawing confirmed. Staining patterns varied between normal adult liver tissue, normal fetal liver tissue and a variety of hepatobiliary diseases. The antibodies provide further evidence of the immunological heterogeneity of the human intrahepatic biliary tree and support the hypothesis that proliferating bile ductules are derived from periseptal hepatocytes. The preparation of the antibodies, their staining reactions in normal adult, normal fetal and a variety of liver diseases are described.

Comparative cytokeratin analysis of sweat gland ducts and eccrine poromas

Human eccrine sweat gland ducts and benign and malignant eccrine poromas were studied for the expression of various cytokeratins (CK) and vimentin by applying immunoperoxidase and immunofluorescence microscopy to frozen or paraffin-embedded sections, and using two-dimensional gel electrophoresis and immunoblotting. In acrosyringia and dermal eccrine ducts, the luminal cells exhibited intense staining for CKs 1/10/11 and 19. The periluminal cell layers of acrosyringia contained CKs 1/10/11, while CK 5 was absent. In contrast, the basal cell layer of dermal ducts was only positive with the antibody against CK 5, i.e. a pattern resembling that seen in epidermal basal cells. CK 9 was detected only in keratinocytes peripherally surrounding acrosyringia. In benign poromas, gel electrophoresis revealed that CKs 5 and 14 were predominant, with CKs 6, 16 and 17 being minor components. At the immunohistochemical level CKs 1/10/11 and 19 could be further detected with varying frequency in scattered or clustered cells and/or duct-like structures. Occasionally, CK 9-positive cells were observed. Malignant poromas displayed a similar overall gel-electrophoretic pattern. Their immunohistochemical staining patterns were also similar to (albeit rather more variable than) those seen in benign poromas. Our results show that, with respect to their CK expression pattern, the majority of poroma cells resemble the basal cells of both the dermal ducts and the epidermis, while only minor and variable subpopulations acquire features present in ductal/acrosyringial luminal cells that would be indicative of poral differentiation. Thus, the matrix cells of poromas seem to be most closely related to basal cells located at the transition between the glandular epidermal ridge and dermal eccrine duct, being in no way analogous to the cells of the adult acrosyringium above the basal cell level.

Immunohistochemical study of cytokeratin distribution in the collecting duct of the human kidney

In order to assess the expression of different cytokeratins in the collecting duct cells (CDCs) of the human kidney, three consecutive sections were stained with periodic acid-Schiff, CAM 5.2 and AE-1 (CAM 5.2 recognizes cytokeratins #19,18,8 and AE-1 #19,16,15,14,10 of Moll's catalog.), respectively. By comparing these sections, it was found that most CDCs in the inner medulla were both CAM 5.2- and AE-1-positive, whereas in the outer medulla and cortex, 77% of the CDCs were both CAM 5.2- and AE-1-positive, 15% CAM 5.2-positive and AE-1-negative, 8% both CAM 5.2- and AE-1-negative, and 0.4% CAM 5.2-negative and AE-1-positive. Recent studies have shown that most CDCs express low-molecular-weight cytokeratins #7,8,18 and 19 (17, 18, 19, 20). Of these cytokeratins, CAM 5.2 recognizes cytokeratins #8,18,19 and AE-1 recognizes cytokeratin #19. Therefore, most CDCs belong to one of the following three major types; 1. Those positive for cytokeratins #8,18 and 19 (CAM 5.2- and AE-1-positive), 2. Those positive for cytokeratins #8 and 18 and negative for #19 (CAM 5.2-positive and AE-1-negative) and 3. Those negative for cytokeratins #8,18 and 19 (CAM 5.2- and AE-1-negative). A few CAM 5.2-negative and AE-1-positive cells were thought to express high-molecular-weight cytokeratins. The significance of these various cytokeratin expressions is discussed.

Cell type-specific and efficient synthesis of human cytokeratin 19 in transgenic mice

In studies designed to identify cis-regulatory elements involved in the cell-type-specific expression of human cytokeratin (CK) genes we have dissected from the major type I CK gene locus on chromosome 17 a region containing the gene that encodes CK 19, with flanking segments of different lengths, and have examined the expression of related gene constructs in transgenic mice. Adult transgenic mice have been characterized by immunohistochemistry, gel-electrophoretic analyses of cytoskeletal proteins and genomic DNA (Southern blots). We have found that a construct harbouring the transcriptional unit plus approximately 0.7 kb downstream from the polyA-addition site and an immediately adjacent 5' upstream segment of approximately 3.6 kb, when combined with a further 5' upstream element of -6.4 - -8.6 kb, is sufficient to guarantee the synthesis of human CK 19 in the same cells and to a similar extent as the murine genome expresses its endogenous CK 19 gene. The findings demonstrate that all cis-elements necessary for the specific and efficient expression of a single type I CK gene, in the context of epithelial differentiation, can be located in the vicinity of the gene itself and that more-distant elements are not required.

Keratin 19 expression in the adult and developing human mammary gland

In the adult human mammary gland, most of the luminal epithelial cells express keratin 19 (K19+). However, in some small ducts and terminal ductal lobular units where branching would be expected to occur during pregnancy, the pattern of expression of this keratin is heterogeneous. While the keratin 19 negative cells (K19-) appear to have a high proliferative potential in vitro and in vivo, they have a lower secretory activity than the K19+ cells as monitored by expression of secretory component in the resting breast or casein in the pregnant gland. That the K19- cells form a separate proliferative compartment in the luminal cell lineage is suggested by the fact that they are absent in the prepubertal breast and only appear at puberty associated with branching ducts, and newly formed lobules. Our observations are consistent with the hypothesis that the K19- luminal cell is less differentiated than and may be precursor to the K19+ luminal cell, which represents the fully differentiated phenotype able to produce milk in response to a hormonal stimulus.

Immunohistochemical interpretation of early epithelial disorders of pyriform sinus

Expression of cytokeratins (CKs) was investigated immunohistochemically by use of monospecific monoclonal anti-CK antibodies in normal epithelia of pyriform sinus and epithelial lesions such as simple hyperplasia, different degrees of dysplasia, in situ carcinoma, and invasive carcinoma. In normal epithelium, strong expression of CK-19 was consistently observed only in the basal layer as basic CK, while expression of CK-13 showed a completely reverse pattern, being expressed only in suprabasal layers as stratification-related CK. Characteristic changes in expression pattern of these two CKs were observed in accordance with the degree of epithelial disorders and differentiation of carcinoma. Cytokeratin 1, as keratinization-associated CK, was observed only in keratinized cells of hyperplastic epithelia and well-differentiated carcinomas. These findings may be useful in evaluating epithelial disorders and classifying carcinomas more objectively, and may assist earlier detection of carcinoma when used with standard histologic techniques.

Abundant expression of cytokeratin 7 in fibrolamellar carcinoma of the liver

Two cases of fibrolamellar carcinoma of the liver, one with lymph node metastasis are reported. Using immunohistochemistry as well as one- and two-dimensional gel electrophoresis and Western blotting, tumour cells of both primary lesions and of the metastasis were found to express cytokeratin polypeptides 8 and 18 and, surprisingly, cytokeratin 7. A small number of cells also expressed cytokeratin 19. This is the first detailed analysis of the cytokeratin expression of fibrolamellar carcinoma, and is also the first to present biochemical evidence that, contrary to what has been suggested, hepatocellular carcinomas do not always preserve the pattern of cytokeratin expression of normal hepatocytes.

Identification of protein IT of the intestinal cytoskeleton as a novel type I cytokeratin with unusual properties and expression patterns

A major cytoskeletal polypeptide (Mr approximately 46,000; protein IT) of human intestinal epithelium was characterized by biochemical and immunological methods. The polypeptide, which was identified as a specific and genuine mRNA product by translation in vitro, reacted, in immunoblotting after SDS-PAGE, only with one of numerous cytokeratin (CK) antisera tested but with none of many monoclonal CK antibodies. In vitro, it formed heterotypic complexes with the type II CK 8, as shown by blot binding assays and gel electrophoresis in 4 M urea, and these complexes assembled into intermediate filaments (IFs) under appropriate conditions. A chymotrypsin-resistant Mr approximately 38,000 core fragment of protein IT could be obtained from cytoskeletal IFs, indicating its inclusion in a coiled coil. Antibodies raised against protein IT decorated typical CK fibril arrays in normal and transformed intestinal cells. Four proteolytic peptide fragments obtained from purified polypeptide IT exhibited significant amino acid sequence homology with corresponding regions of coils I and II of the rod domain of several other type I CKs. Immunocytochemically, the protein was specifically detected as a prominent component of intestinal and gastric foveolar epithelium, urothelial umbrella cells, and Merkel cells of epidermis. Sparse positive epithelial cells were noted in the thymus, bronchus, gall bladder, and prostate gland. The expression of protein IT was generally maintained in primary and metastatic colorectal carcinomas as well as in cell cultures derived therefrom. A corresponding protein was also found in several other mammalian species. We conclude that polypeptide IT is an integral IF component which is related, though somewhat distantly, to type I CKs, and, therefore, we propose to add it to the human CK catalogue as CK 20.

New approaches and concepts in the study of differentiation of oral epithelia

Epithelial structural proteins, the keratins and keratin-associated proteins, are useful as markers of differentiation because their expression is both region-specific and differentiation-specific. In general, basal cells in all stratified oral epithelia express similar keratins, while the suprabasal cells express a specific set of markers indicating commitment to a distinct program of differentiation. Critical factors in the regulation of epithelial protein expression are now under investigation. The promoter regions of keratin genes are being characterized to determine what sequences within the genes are responsible for differential expression. One important extracellular factor that influences epithelial protein expression is retinol (vitamin A), which exerts its effects via a group of nuclear receptor proteins that may also be expressed in a region-specific manner. These molecular biological approaches enhance our understanding of the mechanisms regulating differentiation of oral epithelia and its regional complexity.

Human oral epithelial cell culture. II. Keratin expression in fetal and adult gingival cells

Epithelial cells from human fetal and adult gingiva were cultured in keratinocyte growth medium (KGM), a serum-free medium. The expression of keratin proteins in these cells was evaluated using immunohistochemistry and SDS-PAGE-immunoblot analysis and compared with expression in the tissue. Keratins 5, 6, 14, 16, and 19 were identified in cells cultured from both fetal and adult tissues. K19 was localized in basal cells of fetal oral tissue but was not seen in adult gingiva (except for scattered Merkel cells). K1 and K10 were expressed in tissue, but not in cultured cells. The keratin profiles of cultured epithelial cells from several adult donors were similar and were identical in cultures from primary through Passage 5. K13, a differentiation-specific keratin, was expressed in all suprabasal cells of fetal oral epithelium, but shows only spotty expression in adult gingival tissue. K13 was expressed in cultures of fetal cells, but very weakly or not at all in cultures of adult cells. K13 expression was greater in cultures grown with physiologic calcium concentrations (1.2 mM) than in those grown at 0.15 mM or less. Our findings are consistent with basal-like characters of these cells in 0.15 mM calcium growth conditions. Differentiation of fetal oral cells in culture to the suprabasal basal cell stage in 1.2 mM Ca2+ is shown by the expression of K13.

A cytokeratin-immunohistochemical study of hepatoblastoma

Six cases of hepatoblastoma (five epithelial, one mixed epithelial-mesenchymal) were studied on serially cut cryostat sections, using a panel of monoclonal antibodies directed against individual cytokeratins, vimentin, and desmin, in an indirect immunoperoxidase procedure. Embryonic and fetal-type tumor cells expressed the "hepatocellular" cytokeratins no. 8 and 18 but, surprisingly, also expressed the "bile duct type" cytokeratin no. 19. In addition, two cases had a number of tumor cells which were also positive for the "bile duct type" cytokeratin no. 7. Cells embedded in osteoid-like material were immunoreactive for vimentin but also for cytokeratins no. 7, 18, and 19. Gel electrophoresis, and Western blotting of cytoskeletal extracts, confirmed the immunohistochemical data. The implications of these findings for the histogenesis of hepatoblastoma are discussed in this report.

Extensive changes in cytokeratin expression patterns in pathologically affected human gingiva

The stratified squamous epithelium of the oral gingiva and the hard palate is characterized by a tissue architecture and a cytoskeletal composition similar to, although not identical with, that of the epidermis and fundamentally different from that of the adjacent non-masticatory oral mucosa. Using immunocytochemistry with antibodies specific for individual cytokeratins, in situ hybridization and Northern blots of RNA with riboprobes specific for individual cytokeratin mRNAs, and gel electrophoresis of cytoskeletal proteins of microdissected biopsy tissue samples, we show changes in the pattern of expression of cytokeratins and their corresponding mRNAs in pathologically altered oral gingiva. Besides a frequently, although not consistently, observed increase in the number of cells producing cytokeratins 4 and 13 (which are normally found as abundant components in the sulcular epithelium and the alveolar mucosa but not in the oral gingiva) and a reduction in the number of cells producing cytokeratins 1, 10 and 11, the most extensive change was noted for cytokeratin 19, a frequent cytokeratin in diverse one-layered and complex epithelia. While in normal oral gingiva cytokeratin 19 is restricted to certain, sparsely scattered cells of --or near--the basal cell layer, probably neuroendocrine (Merkel) cells, in altered tissue of inflamed samples it can appear in larger regions of the basal cell layer(s) and, in apparently more advanced stages, also in a variable number of suprabasal cells. Specifically, our in situ hybridization experiments show that this altered suprabasal cytokeratin 19 expression is more extended at the mRNA than at the protein level, indicating that cytokeratin 19 mRNA synthesis may be a relatively early event during the alteration. These changes in cytokeratin expression under an external pathological influence are discussed in relation to other factors known to contribute to the expression of certain cytokeratins and with respect to changes occurring during dysplasia and malignant transformation of oral epithelia.

A cytokeratin-immunohistochemical study of focal nodular hyperplasia of the liver: further evidence that ductular metaplasia of hepatocytes contributes to ductular "proliferation"

A cytokeratin-immunohistochemical study was performed on eight specimens of focal nodular hyperplasia of the liver in order to determine whether hepatocytes in this lesion can express "bile duct type" cytokeratins. Serially cut cryostat sections were reacted with a panel of six monoclonal antibodies specifically reactive with cytokeratin polypeptides nr. 7, 8, 18 and 19, using a 3-step immunoperoxidase procedure. Hepatocytes were positive for cytokeratins nr. 8 and nr. 18, whereas ductules contained in addition to cytokeratins nr. 8 and nr. 18 also polypeptides nr. 7 and nr. 19. In all cases, a variable number of hepatocytes close to fibrous septa or inside the nodules expressed cytokeratin nr. 7. In four cases, a small number of hepatocytes were also immunoreactive for cytokeratin nr. 19. Our data demonstrate that hepatocytes in focal nodular hyperplasia can express one or even two "bile duct type" cytokeratins, supporting the concept that ductular metaplasia of hepatocytes contributes to the ductular "proliferation" observed in this tumor-like lesion.

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

Keratins K14 and K5 have long been considered to be biochemical markers of the stratified squamous epithelia, including epidermis (Moll, R., W. Franke, D. Schiller, B. Geiger, and R. Krepler. 1982. Cell. 31:11-24; Nelson, W., and T.-T. Sun. 1983. J. Cell Biol. 97:244-251). When cells of most stratified squamous epithelia differentiate, they downregulate expression of mRNAs encoding these two keratins and induce expression of new sets of keratins specific for individual programs of epithelial differentiation. Frequently, as in the case of epidermis, the expression of differentiation-specific keratins also leads to a reorganization of the keratin filament network, including denser bundling of the keratin fibers. We report here the use of monospecific antisera and cRNA probes to examine the differential expression of keratin K14 in the complex tissue of human skin. Using in situ hybridizations and immunoelectron microscopy, we find that the patterns of K14 expression and filament organization in the hair follicle are strikingly different from epidermis. Some of the mitotically active outer root sheath (ORS) cells, which give rise to ORS under normal circumstances and to epidermis during wound healing, produce only low levels of K14. These cells have fewer keratin filaments than basal epidermal cells, and the filaments are organized into looser, more delicate bundles than is typical for epidermis. As these cells differentiate, they elevate their expression of K14 and produce denser bundles of keratin filaments more typical of epidermis. In contrast to basal cells of epidermis and ORS, matrix cells, which are relatively undifferentiated and which can give rise to inner root sheath, cuticle and hair shaft, show no evidence of K14, K14 mRNA expression, or keratin filament formation. As matrix cells differentiate, they produce hair-specific keratins and dense bundles of keratin filaments but they do not induce K14 expression. Collectively, the patterns of K14 and K14 mRNA expression and filament organization in mitotically active epithelial cells of the skin correlate with their relative degree of pluripotency, and this suggests a possible basis for the deviation of hair follicle programs of differentiation from those of other stratified squamous epithelia.

A cytokeratin immunohistochemical study of cholestatic liver disease: evidence that hepatocytes can express 'bile duct-type' cytokeratins

A cytokeratin immunohistochemical study was performed on 38 liver biopsies from cases of primary biliary cirrhosis, primary sclerosing cholangitis, extrahepatic biliary obstruction or drug-induced liver disease in order to analyse the cytoskeletal changes in detail. On paraffin sections of 27 cases, a variable number of hepatocytes were reactive with a polyclonal anti-cytokeratin antiserum that, in the normal liver, stains bile duct cells only. On cryostat sections of 23 cases, a variable number of hepatocytes were immunoreactive with a monoclonal antibody specifically directed against cytokeratin no. 7 and were most numerous in cases of long-standing cholestasis irrespective of the aetiology. In three cases of primary sclerosing cholangitis and two cases of primary biliary cirrhosis a few hepatocytes were also weakly positive with a monoclonal antibody specific for cytokeratin no. 19. Since cytokeratins no. 7 and no. 19 are, in the normal liver, restricted to bile duct cells, these results further support the concept of 'ductular metaplasia' of hepatocytes, the mechanism of which remains unclear.

Immunohistochemistry of dysplasias and carcinomas of the esophageal epithelium

Two types of high grade dysplasia were associated with invasive carcinomas. The first, deeply localized, had a pagetoid appearance and a particular phenotype: the dysplastic cells had keratins of low molecular weight rarely present in the esophagus; keratins of stratified epithelia were absent. This dysplasia was probably the origin of undifferentiated invasive carcinoma with which it was often associated. The second type, transepithelial, extended through the entire thickness of the epithelium. The abnormal cells presented some differentiation and stained positive for keratins of stratified epithelia. This dysplasia was often associated with differentiated squamous cell carcinoma. An intermediate-type dysplasia shared some characteristics with both main types. Several types of dysplasia and several areas of differently differentiated carcinoma were often associated in the same case. The evolutional potential of the different dysplasias is not known.

Secretory component in differentiating normal epithelium, benign lesions and malignancy in the human breast as monitored by monoclonal antibodies

An immunohistochemical study of the expression of the secretory component (SC) in human mammary gland epithelium at various stages of differentiation, as well as in benign and malignant breast tumours, was undertaken using three mouse monoclonal antibodies. Antibody RICEO-SC-05 (SC-05), raised against a partially purified preparation of human SC, and reacting with a reduction-resistant epitope present in both free and polymeric immunoglobulin-bound SC, was compared in immunoperoxidase and immunofluorescence studies on a diverse range of normal tissues, to 2 reference anti-SC antibodies (LICR-LONLC28 and RICEO-MFG-12). All three antibodies reacted with secretory epithelia only, consistent with known patterns of expression of SC in tissues, although there was an unexpected reaction by all anti-SC antibodies with some Hassal's corpuscles of the thymus. Staining patterns seen in the normal resting, pregnant, lactating and regressing (after weaning) breast provide evidence for differentiation-associated changes in the production of SC, and support the concept of terminal ductal lobular units (TDLUs) as functional compartments of the mammary gland. SC was detected in all but one benign breast lesion (n = 53) as compared to only 24% positive cases with heterogeneous expression of SC found among 176 primary and metastatic breast carcinomas examined. In a series of 40 primary breast carcinomas and their corresponding lymph node metastases, a good overall correlation was found between the expression of SC in the matched specimens; aside from 3 heterogeneously SC-positive carcinomas whose metastatic counterparts were SC-negative. Our results demonstrate a potential application for monoclonal antibodies to SC in the study of human mammary gland differentiation, but suggest that the value of an assay for SC in the diagnosis of breast carcinomas is questionable due to the generally low expression of SC by either primary or metastatic breast lesions.

Keratin 19: predicted amino acid sequence and broad tissue distribution suggest it evolved from keratinocyte keratins

The type I keratin 19 is unusual in its tissue distribution in that under normal circumstances it does not seem to be restricted, as the other keratins are, to expression in either stratified or simple epithelia. In addition to the previously reported distribution of keratin 19 in human tissues, we have observed keratin 19 in epidermal basal cells, in a defined region of the hair follicle, and in nipple epidermis. We noticed that expression of keratin 19 appears to be especially characteristic of regions of labile or variable cellular differentiation as indicated by the presence of multiple keratin phenotypes in close proximity to each other. Using a monoclonal antibody recognizing keratin 19 (LP2K) to screen a human placenta cDNA expression library, we have isolated, cloned, and sequenced cDNA coding for full-length human keratin 19, as confirmed by its reactivity with several other known anti-keratin 19 monoclonal antibodies and by the near identity of its sequence with that of the bovine keratin 19 homologue. This similarity extends to both proteins being truncated at the C-terminal end to only 13 amino acids beyond the rod domain. Although the amino acid homology over the N-terminal and helical rod domains is particularly high, the human and bovine proteins diverge substantially over the short C-terminal domain, which suggests that this region has no conserved function. Comparison with other type I keratins indicates that the closest evolutionary neighbors of keratin 19 are keratinocyte keratins, probably 13 and 14, and not the simple epithelial keratin 18. Assessing the histochemistry and sequence data together, we propose that the cell may use this apparently deficient keratin as a "neutral" keratin. While unimpaired in its ability to polymerize (keeping the cell integrated into the epithelial sheet via filament-desmosome networks), keratin 19 expression does not irrevocably commit a cell to any one of the local differentiation options. Such predicted differentiational flexibility may also imply vulnerability to transformation.

Immunohistochemical distribution of keratin proteins in clinically healthy human gingival epithelia

In clinically healthy/subclinically inflamed biopsies of marginal gingiva, the immunohistochemical distribution of keratin proteins was studied in junctional (JE), sulcular (SE), oral gingival (OGE) and in a few samples of alveolar mucosal epithelium (AE) by means of various mouse monoclonal anti-keratin antibodies in an indirect fluorescence technique. All regions stained in a nearly similar way with AE3 (keratins 1-8, all cells) and BE14 (keratin 5, basal and supra/parabasal cells). AE8-staining (keratin 13, supra/parabasal and spinous cells) was primarily confined to the stratified, nonkeratinized epithelia SE and AE, but also a variable part of JE and less frequently OGE were positive. The parakeratinized OGE was distinct in showing a homogeneous staining with AE2 (keratins 1/2, 10) and AE5 (keratin 3) throughout spinous cell layers. These antibodies did not stain JE and AE whereas SE stained in a scattered way with AE5 and sometimes also with AE2. The latter finding might indicate initial keratinization at molecular level. The JE was distinct in retaining basal characteristics throughout the epithelium with PKK2 (keratin 7, 16, 17, 19) and BE14 (keratin 5) although some initial suprabasal maturation, as observed with AE8, cannot be excluded. Differences in keratin staining of gingival epithelia and the AE was found with respect to AE1-reactivity (keratins 10, 14-16, 19) which was suprabasal in JE, SE and OGE but basal in AE.

A comparative biochemical and immunological analysis of cytokeratin patterns in the oral epithelium of the miniature pig and man

In man, cytokeratin constitutes a family of 19 polypeptides that show different but distinct distribution patterns in the various epithelia. Changes in these patterns may occur during epithelial development and differentiation. The cytokeratin patterns in the oral mucosa of the miniature pig, an animal used in studies of wound healing, were investigated. Surgical biopsies were obtained from the gingiva, hard palate and alveolar mucosa of both man and pig. The cytokeratins were analysed by immunofluorescence, two-dimensional gel electrophoresis and by immunoblotting. Nine monoclonal antibodies were used to identify the different cytokeratin polypeptides in cryostat sections. Two-dimensional gel electrophoresis showed that pig oral mucosa contains at least 10 different polypeptides, five of the acidic type I and five of the basic type II cytokeratins. These were different from the human cytokeratin polypeptides and accordingly were designated P1-P10, according to their molecular weight and isoelectric mobility. Their molecular weight varied between 48 and 69 kdalton and the pHi varied between 5 and 7.3. Immunoblotting showed the monoclonal antibody Ks 13.1 (anticytokeratins Nos 13 and 14) to cross-react with the pig polypeptides P10 and P8. Immunolocalization showed that all the antibodies cross-reacted with the pig tissue except Ks 19.1 (anticytokeratin No. 19). It was possible to differentiate between pig alveolar mucosa, which expressed only P3, P4, P5, P8 and P10, and the gingival and hard palatal mucosae, which expressed all 10 polypeptides except P5. This distinction was made by antibody 6B10 (anticytokeratin No. 4), which reacted only with alveolar mucosa; antibody Ks 13.1, which strongly reacted with uncornified mucosa but weakly with cornified mucosa (gingiva and palate); and any of RKSE60, Kk 8.60 or EE21.6 (anticytokeratin No. 10, anticytokeratins Nos 10 and 11 and anticytokeratins Nos 1, 2, 10 and 11, respectively), which reacted strongly with cornified mucosa but weakly, if at all, with uncornified mucosa. These findings provide a baseline for studies on epithelial differentiation in the miniature pig such as in wound healing.

Cytokeratin expression in experimental murine rhabdomyosarcomas. Intermediate filament pattern in original tumors, allotransplants, cell culture and re-established tumors from cell culture

Soft tissue sarcomas were induced by 20-methylcholanthrene in NMRI-mice. The tumors were characterized as rhabdomyosarcomas by light and electron microscopy as well as immunohistochemistry (vimentin, desmin and myoglobin expression). Cytokeratins could be demonstrated by a panel of different poly- and monoclonal antibodies in original rhabdomyosarcomas, their allotransplants and the re-established tumors from cell culture in nude mice. The cytokeratin positive tumor cells were arranged in small clusters and/or haphazardly single dispersed in the rhabdomyosarcomas. By means of monoclonal antibodies cytokeratins No. 8 and No. 19 could be evidenced and cytokeratin No. 18 could be made probably. Behind the background of cytokeratin expression in developing fetal cross striated muscle cells our findings are discussed as a reminiscence of embryonal muscle development in these tumors. The significance of cytokeratin expression in rhabdomyosarcomas for diagnostic histopathology is emphasized.

Epithelial cell markers and proliferating cells in odontogenic jaw cysts

The expression of keratins, CEA, EMA, and rat liver antigen (RLA) and the presence of Ki67+ proliferating cells were studied in the epithelial linings of 50 odontogenic cysts using an indirect immunoperoxidase method on acetone-fixed frozen sections. All cysts were positive with monoclonal antibodies of broad keratin specificity (CK1, AE1-3), and between 40 and 100 per cent of epithelial cells expressed keratins 13 and 19. Keratins 7, 8, and 18 were rarely expressed although surface cells in areas of mucous metaplasia often expressed keratins 7 and 18. Expression of keratin 10/11 was related to the presence of a well-ordered epithelial lining and was detected in isolated cells in 4/32 non-keratinizing cysts and in the upper suprabasal cell layers of 17/18 keratocysts. Although CEA, EMA, and RLA were detected in the epithelium of all specimens, the pattern of expression of CEA and EMA differed between cyst types. Ki67+ proliferating cells were most prevalent in keratocyst epithelia, where they were usually found within lower suprabasal layers which were negative or weakly positive for keratins 10/11 and 13. These results indicate differences in keratin, CEA, and EMA expression between cyst types which appear to be dependent on epithelial differentiation/structure rather than cyst type or histogenesis. Although these differences may not be of diagnostic significance, the consistent expression of both keratins 13 and 19 may provide a useful marker of odontogenic epithelium in general.