Cell type heterogeneity of intermediate filament expression in epithelia of the human pituitary gland

In the present study we have localized immunohistochemically the intermediate filament proteins of the human pituitary gland (adenohypophysis, pars intermedia and pars tuberalis) by an indirect immunoperoxidase technique or by double immunofluorescence methods and analysed the individual cytokeratin polypeptides using two-dimensional gel electrophoresis. We found that the expression of cytokeratins in different epithelial cells of the human anterior pituitary gland was heterogeneous. Whereas the endocrine cells only expressed cytokeratins 8 and 18, the folliculo-stellate cells exhibited a reactivity for cytokeratins 7, 8, 18 and 19 as well as for GFAP and vimentin. The squamous epithelial cells of the pars tuberalis and the Ratke's cysts showed a more complex cytokeratin pattern of both squamous and simple type. Whereas in may cystic epithelial cells including the "pseudo-follicles" a triple expression of cytokeratin, vimentin and GFAP could be observed, only some basal cells of squamous epithelial nests coexpressed cytokeratin and vimentin. The differences in the intermediate filament protein distribution are discussed in the light of embryological relationships of the different parts of the human pituitary gland.     

Cell type heterogeneity of intermediate filament expression in epithelia of the human pituitary gland

Summary In the present study we have localized immunohistochemically the intermediate filament proteins of the human pituitary gland (adenohypophysis, pars intermedia and pars tuberalis) by an indirect immunoperoxidase technique or by double immunofluorescence methods and analysed the individual cytokeratin polypeptides using two-dimensional gel electrophoresis. We found that the expression of cytokeratins in different epithelial cells of the human anterior pituitary gland was heterogeneous. Whereas the endocrine cells only expressed cytokeratins 8 and 18, the folliculo-stellate cells exhibited a reactivity for cytokeratins 7, 8, 18 and 19 as well as for GFAP and vimentin. The squamous epithelial cells of the pars tuberalis and the Ratke's cysts showed a more complex cytokeratin pattern of both squamous and simple type. Whereas in many cystic epithelial cells including the pseudo-follicles a triple expression of cytokeratin, vimentin and GFAP could be observed, only some basal cells of squamous epithelial nests coexpressed cytokeratin and vimentin. The differences in the intermediate filament protein distribution are discussed in the light of embryological relationships of the different parts of the human pituitary gland.     

Monoclonal antibodies to human cytokeratins: application to various epithelial and mesothelial cells

Immunohistological analysis of human tissue using monoclonal antibodies against cytokeratins, which are confined to cells of epithelial origin, is a valuable technique. Using human epidermal keratins as antigen, we prepared monoclonal antibodies against cytokeratins (ZK1, ZK7, ZK61 and ZK99) and against a desmosomal protein (ZK31). Immunohistochemical staining of human skin sections using these antibodies showed a specific reaction with the epidermis: ZK1 stained the entire epidermis, ZK7 only the basal layer, ZK61 and ZK99 the suprabasal layers, and ZK31 the cellular interfaces. In order to test for antibody specificity, immunoblots with human epidermal and amnion epithelial cytokeratin polypeptides, as well as immunofluorescence microscopy of simple epithelia (glandular and simple columnar epithelia) were performed. ZK1, ZK61 and ZK99 reacted preferentially with cytokeratin polypeptides of stratified squamous epithelia and ZK7 recognized cytokeratins of stratified and simple epithelia. When the ZK antibodies were tested on mesothelial cells in pleural effusions, only ZK7 reacted with these cells. Biochemical analysis of cytokeratin accumulation in cells of primary and long-term cultures indicated that the cytokeratin pattern of mesothelial cells was quite unstable, while that of amnion epithelial cells showed only minor quantitative changes. The use of these antibodies to determine the epithelial origin of cells present in pleural effusions is proposed.     

Cytokeratin expression in human thymus: immunohistochemical mapping

Cytokeratin expression in normal postnatal human thymus was studied immunohistochemically by using monoclonal antibodies against various cytokeratin polypeptides. An attempt was made to characterize cell populations giving rise to the cornified structures of Hassal's corpuscles. Monoclonal antibody KB-37, a marker of squamous epithelium basal cells, was applied to distinguish the earliest cells capable of undergoing squamous differentiation. Parts of the subcapsular epithelium were extensively stained with this reagent. This epithelium, like the basal layer of certain squamous epithelia, exibited a high incidence of cytokeratins 13 and 14, and pronounced expression of cytokeratin 19. Simple epithelium cytokeratins 8, 18, and 19 were present in the cortex. Scattered cells reacted with KB-37 antibody. All stellate epithelial cells in the medulla were positive for cytokeratin 19. Most of the medullar epithelial cells were positive for cytokeratins 13, 14 and 17 of complex epithelium, in contrast to the cortex, where only a few cells were positive for these cytokeratins. A significant proportion of the medullar cells was positive for KB-37 antigen. Cytokeratins 8 and 18 were expressed in single cells and in groups of cells surrounding Hassal's corpuscles. The outermost cells of these corpuscles were positive for cytokeratin 19 and KB-37. In the peripheral parts of Hassal's corpuscles, simple epithelium cytokeratins 7, 8, 18, and cytokeratins 4, 13, 14, and 17, characteristic of stratified nonkeratinizing epithelia, were coexpressed with keratinization-specific cytokeratins 10/11. The inner parts of the swirls were uniformly positive for cytokeratins was reduced.     

Expression of intermediate filament proteins in fetal and adult human lung tissues

The expression patterns of intermediate filament proteins in fetal and normal or nonpathological adult human lung tissues are described using (chain-specific) monoclonal antibodies. In early stages of development (9-10 weeks and 25 weeks of gestation) only so-called simple cytokeratins such as cytokeratins 7 (minor amounts). 8, 18 and 19 are detected in bronchial epithelial cells. At later stages of development, the cytokeratin expression patterns become more complex. The number of bronchial cells positive for cytokeratin 7 increases, but basal cells in the bronchial epithelium remain negative. These latter cells show, however, expression of cytokeratin 14 in the third trimester of gestation. Developing alveolar epithelial cells express cytokeratins 7, 8, 18 and 19. In adult human bronchial epithelium cytokeratins 4 (varying amounts), 7, 8, 13 (minor amounts), 14, 18 and 19 can be detected, with the main expression of cytokeratins 7, 8, and 18 in columnar cells and the main expression of cytokeratin 14 in basal cells. Vimentin is detected in all mesenchymal tissues. In addition, fetal lung expresses vimentin in bronchial epithelium, however, to a lesser extent with increasing age, resulting in the expression of vimentin in only few scattered bronchial cells at birth. Also in adult bronchial epithelium the expression of vimentin is noticed in part of the basal and columnar epithelial cells. Desmin filaments, present in smooth muscle cells of the lung, appear to alter their protein structure with age. In early stages of development smooth muscle cells surrounding blood vessels are partly reactive with some cytokeratin antibodies and with a polyclonal desmin antibody. At week 9-10 and week 25 of gestation a monoclonal antibody to desmin, however, is not reactive with blood vessel smooth muscle cells but is only reactive with smooth muscle cells surrounding bronchi. With increasing age the reactivity of cytokeratin antibodies with smooth muscle cells in blood vessels decreases, while the reactivity with the monoclonal desmin antibody increases. Our results show that during differentiation profound changes in the intermediate filament expression patterns occur in the different cell types of the developing lung.     

Monoclonal antibodies to various acidic (type I) cytokeratins of stratified epithelia

We determined the reactivity of two monoclonal antibodies to cytokeratins that are typically expressed in certain stratified epithelia and several human squamous cell carcinomas using immunoblotting techniques and immunofluorescence microscopy. Antibody KS 8.12 reacted specifically with cytokeratin polypeptides nos. 13 and 16, and stained noncornified squamous epithelia in a rather uniform way. The examination of diverse human carcinomas showed all squamous cell carcinomas to be positively stained with this antibody, whereas all adenocarcinomas were negative. Another antibody, KK 8.60, reacted with polypeptides nos. 10 and 11, and uniformly stained the suprabasal layers of the epidermis. In several noncornified squamous epithelia (e.g., tongue, exocervix), in thymus reticulum epithelial cells, and in moderately and well differentiated squamous cell carcinomas this antibody exhibited a nonuniform labeling pattern that allowed the detection of individual cytokeratin-10/11-positive cells scattered throughout the tissue. It is concluded that antibodies KS 8.12 and KK 8.60 represent specific molecular probes for the definition of certain stages of squamous differentiation in normal development as well as in pathological processes such as squamous metaplasia and carcinogenesis. We propose the use of these antibodies in the differential diagnosis of carcinomas and their metastases.     

Expression of simple epithelial type cytokeratins in stratified epithelia as detected by immunolocalization and hybridization in situ

Multi-layered ("stratified") epithelia differ from one-layered ("simple") polar epithelia by various architectural and functional properties as well as by their cytoskeletal complements, notably a set of cytokeratins characteristic of stratified tissue. The simple epithelial cytokeratins 8 and 18 have so far not been detected in any stratified epithelium. Using specific monoclonal antibodies we have noted, in several but not all samples of stratified epithelia, including esophagus, tongue, exocervix, and vagina, positive immunocytochemical reactions for cytokeratins 8, 18, and 19 which in some regions were selective for the basal cell layer(s) but extended into suprabasal layers in others. In situ hybridization with different probes (riboprobes, synthetic oligonucleotides) for mRNAs of cytokeratin 8 on esophageal epithelium has shown, in extended regions, relatively strong reactivity for cytokeratin 8 mRNA in the basal cell layer. In contrast, probes to cytokeratin 18 have shown much weaker hybridization which, however, was rather evenly spread over basal and suprabasal strata. These results, which emphasize the importance of in situ hybridization in studies of gene expression in complex tissues, show that the genes encoding simple epithelial cytokeratins can be expressed in stratified epithelia. This suggests that continual expression of genes coding for simple epithelial cytokeratins is compatible with the formation of squamous stratified tissues and can occur, at least in basal cell layers, simultaneously with the synthesis of certain stratification-related cytokeratins. We also emphasize differences of expression and immunoreactivity of these cytokeratins between different samples and in different regions of the same stratified epithelium and discuss the results in relation to changes of cytokeratin expression during fetal development of stratified epithelia, in response to environmental factors and during the formation of squamous cell carcinomas.     

Cytokeratins in normal lung and lung carcinomas. I. Adenocarcinomas, squamous cell carcinomas and cultured cell lines

The various epithelial cells of the lower respiratory tract and the carcinomas derived from them differ markedly in their differentiation characteristics. Using immunofluorescence microscopy and two-dimensional gel electrophoresis of cytoskeletal proteins from microdissected tissues we have considered whether cytokeratin polypeptides can serve as markers of cell differentiation in epithelia from various parts of the human and bovine lower respiratory tract. In addition , we have compared these protein patterns with those found in the two commonest types of human lung carcinoma and in several cultured lung carcinoma cell lines. By immunofluorescence microscopy, broad spectrum antibodies to cytokeratins stain all epithelial cells of the respiratory tract, including basal, ciliated, goblet, and alveolar cells as well as all tumor cells of adenocarcinomas and squamous cell carcinomas. However, in contrast, selective cytokeratin antibodies reveal cell type-related differences. Basal cells of the bronchial epithelium react with antibodies raised against a specific epidermal keratin polypeptide but not with antibodies derived from cytokeratins characteristic of simple epithelia. When examined by two-dimensional gel electrophoresis, the alveolar cells of human lung show cytokeratin polypeptides typical of simple epithelia (nos. 7, 8, 18 and 19) whereas the bronchial epithelium expresses, in addition, basic cytokeratins (no. 5, small amounts of no. 6) as well as the acidic polypeptides nos. 15 and 17. Bovine alveolar cells also differ from cells of the tracheal epithelium by the absence of a basic cytokeratin polypeptide. All adenocarcinomas of the lung reveal a "simple-epithelium-type" cytokeratin pattern (nos. 7, 8, 18 and 19). In contrast, squamous cell carcinomas of the lung contain an unusual complexity of cytokeratins. We have consistently found polypeptides nos. 5, 6, 8, 13, 17, 18 and 19 and, in some cases, variable amounts of cytokeratins nos. 4, 14 and 15. Several established cell lines derived from human lung carcinomas (SK-LU-1, Calu -1, SK-MES-1 and A-549) show a uniform pattern of cytokeratin polypeptides (nos. 7, 8, 18 and 19), similar to that found in adenocarcinomas. In addition, vimentin filaments are produced in all the cell lines examined, except for SK-LU-1.(ABSTRACT TRUNCATED AT 400 WORDS)     

Changes in the Pattern of Cytokeratin Polypeptides in Epidermis and Hair Follicles During Skin Development in Human Fetuses

Abstract. The cytokeratin polypeptides of microdissected epidermis and hair follicles from human fetuses (from week 10 of pregnancy until birth) have been analysed by two-dimensional gel electrophoresis. Two-layered epidermis in 10-week fetuses contains major amounts of cytokeratin polypeptides typical of simple epithelia (components Nos. 8, 18, and 19 according to Moll et al. [31]). These cytokeratins are gradually reduced in their relative amounts and eventually disappear in the multilayered epidermis of later stages. At advanced stages of development, cytokeratins characteristic of adult epidermis are detected and finally predominate. These include the large and basic epidermal cytokeratin No. 1 (apparent molecular weight 68,000) which is already present in the three-layered epidermis of 13-week fetuses. Hair follicle germ cells of 13-week fetuses differ from fetal epidermal keratinocytes and show a very simple cytokeratin pattern, dominated by only two major polypeptides (Nos. 5 and 17). More developed hair follicles of 20-week fetuses have established a cytokeratin pattern similar to, but not identical with, that of hair follicles from adult skin. Different staining patterns obtained by indirect immunofluorescence microscopy using cytokeratin antibodies with different specificities suggest that, in three-layered epidermis, different cytokeratin patterns might exist in the specific cell layers. Such a differential location might explain the high complexity of polypeptide components found in fetal skin. Possible contributions of peridermal cytokeratins to this complex pattern of fetal epidermis are discussed.     

Characterization of subcolumnar reserve cells and other epithelia of human uterine cervix. Demonstration of diverse cytokeratin polypeptides in reserve cells

We have analyzed the expression of cytokeratin polypeptides in subcolumnar reserve cells of the human uterine endocervical mucosa and the other epithelial cells using immunoperoxidase and immunofluorescence microscopy as well as by applying two-dimensional gel electrophoresis to microdissected cytoskeletal preparations. Endocervical columnar cells were uniformly positive for antibodies directed against the simple epithelium-type cytokeratins nos. 7, 8, 18, and 19, while a variable proportion of these cells was stained by an antibody against cytokeratin no. 4. Reserve cells were not only positive for cytokeratins nos. 8 (weakly and variably) and 19 but were also decorated by antibody KA 1, which reacts with cytokeratins present in stratified squamous epithelia. This last antibody selectively decorated reserve cells even when they were flat and inconspicuous. Antibody KA 1 uniformly stained the ectocervical squamous epithelium, the basal cells of which were also decorated by antibodies directed against cytokeratins nos. 8 (weakly and variably) and 19. Ectocervical suprabasal cells were positive, to a variable extent, for antibodies against cytokeratins nos. 4, 10/11, and 13. Gel electrophoresis revealed the presence of squamous-type cytokeratins nos. 5 and 17 in reserve cell-rich, but not in reserve cell-free, endocervical mucosa. We also analyzed the distribution pattern of these cells, as revealed by antibody KA 1, in the endocervical mucosa of 26 uteri. In all the specimens examined reserve cells were present, but their numbers exhibited considerable variation. In some cases these cells were confined to small islets localized deep within the cervical canal and lacked any continuity with the squamous epithelium. The expression of cytokeratins nos. 5 and 17 in reserve cells indicates that these cells have undergone a low level of squamous differentiation. The additional expression of cytokeratins nos. 8 and 19 in these cells points to a relationship with simple epithelial cells. The present data would seem to favor the view that reserve cells originate in situ from the columnar epithelium; however, this would imply an acquisition of new differentiation properties.     

The pattern of cytokeratin synthesis is a marker of type 2 cell differentiation in adult and maturing fetal lung alveolar cells

During the last stages of fetal life, the immature epithelial cells of the rat lung alveolus develop the properties of mature type 2 cells. Adult type 2 cells rapidly lose these same properties when isolated and maintained in cell culture. We have examined the synthesis of cytokeratin proteins by adult type 2 cells as they lose their differentiated characteristics during 1 week in culture, and of immature fetal alveolar epithelial cells as they differentiate either in utero or when cultured on an extracellular matrix. Freshly isolated adult type 2 cells synthesize four cytokeratins which by electrophoretic mobilities and Western blot analysis correspond to human cytokeratins Nos. 7, 8, 18, and 19. During 7 days in culture synthesis of cytokeratin No. 19 is dramatically decreased and cytokeratin No. 18 becomes the predominant acidic cytokeratin produced. Fetal lung epithelial cells at 18 days gestation lack most characteristics of mature type 2 cells. When freshly isolated, these cells synthesize cytokeratins Nos. 7, 8, and 18 but make only minimal amounts of cytokeratin No. 19. When these cells are allowed to mature either in utero or in culture on a whole basement membrane extract, they develop both the morphological characteristics and the pattern of cytokeratin synthesis of fully developed type 2 cells, with cytokeratins No. 19 being the major acidic cytokeratin produced.     

Alterations in cytokeratin expression precede histological changes in epithelia of vitamin A-deficient rats

Summary Normal epithelial cell differentiation is charactezied by the production of distinct cytokeratin proteins. It is well known that epithelia of several organs show squamous metaplasia in a vitamin A-deficient status. It is not yet known whether these histological changes are concomitant with a change in cytokeratin expression. Therefore, 3-week-old female rats (BN/BiRij) were fed a vitamin A-deficient diet for 8 weeks. The cytokcratin expression in epithelia of various organs was monitored immunohistochemically during the induction of vitamin A deficiency. Therefore, monoclonal antibodies specific for human cytokeratin 4, 5, 5+8, 7, 10, 14, 18 and 19 were used. In a normal vitamin A status, the distributional pattern for the different cytokeratins in rats was similar to that reported for human tissue. No change in cytokeratin expression was seen in trachea, skin, liver and colon at any time point studied. Squamous metaplasia in urinary bladder and salivary glands was observed after six weeks on the vitamin A-deficient diet. This was concomitant with a substitution of cytokeratins 4, 5+8, 7, 18 and 19 by cytokeratin 10. The latter cytokeratin is specific for keratinzed squamous epithelium. A change in cytokeratin expression was observed in bladder, ureter, kidney, salivary glands, uterus and conjunctiva before histological alterations appeared. In conclusion, the changes in cytokeratin expression observed under vitamin A deficiency in epithelia in vivo are in agreement with those described in other studies for epithelial cells in vitro. The changes in cytokeratin expression and the subsequent differentiation into squamous cells occurs in basal cells of the bladder but not in transitional cells. Furthermore, histological alterations are preceded by changes in cytokeratin expression indicating that vitamin A status controls cytokeratin expression in vivo.     

Diversity of cytokeratins. Differentiation specific expression of cytokeratin polypeptides in epithelial cells and tissues

Epithelial cells contain a cytoskeletal system of intermediate-sized (7 to 11 nm) filaments formed by proteins related to epidermal keratins (cytokeratins). Cytoskeletal proteins from different epithelial tissues (e.g. epidermis and basaliomas, cornea, tongue, esophagus, liver, intestine, uterus) of various species (man, cow, rat, mouse) as well as from diverse cultured epithelial cells have been analyzed by one and two-dimensional gel electrophoresis. Major cytokeratin polypeptides are identified by immunological cross-reaction and phosphorylated cytokeratins by [³²P]phosphate labeling in vivo.It is shown that different epithelia exhibit different patterns of cytokeratin polypeptides varying in molecular weights (range: 40,000 to 68,000) and electrical charges (isoelectric pH range: 5 to 8.5). Basic cytokeratins, which usually represent the largest cytokeratins in those cells in which they occur, have been found in all stratified squamous epithelia examined, and in a murine keratinocyte line (HEL) but not in hepatocytes and intestinal cells, and in most other cell cultures including HeLa cells. Cell type-specificity of cytokeratin patterns is much more pronounced than species diversity. Anatomically related epithelia can express similar patterns of cytokeratin polypeptides. Carcinomas and cultured epithelial cells often continue to synthesize cytokeratins characteristic of their tissue of origin but may also produce, in addition or alternatively, other cytokeratins. It is concluded: (1) unlike other types of intermediate-sized filaments, cytokeratin filaments are highly heterogeneous in composition and can contain basic polypeptides: (2) structurally indistinguishable filaments of the same class, i.e. cytokeratin filaments, are formed, in different epithelial cells of the same species, by different proteins of the cytokeratin family; (3) vertebrate genomes contain relatively large numbers of different cytokeratin genes which are expressed in programs characteristic of specific routes of epithelial differentiation; (4) individual cytokeratins provide tissue- or cell type-specific markers that are useful in the definition and identification of the relatedness or the origin of epithelial and carcinoma cells.     

Heterogeneity in the immunolocalization of cytokeratin specific monoclonal antibodies in the rat eye: evaluation of unusual epithelial tissue entities

Summary The immunocytochemical localization of cytokeratin and vimentin in rat eye tissues was investigated using a panel of 39 monoclonal antibodies specific for single or multiple of cytokeratin polypeptides and one polyclonal anti CK20 antiserum. The retinal and the ciliary body pigment epithelia only expressed cytokeratins 8 and 18, whereas the fetal retinal pigment epithelium and focally the adult epithelium, in the transition zone of retina and ciliary body, exhibited a reactivity for cytokeratin 19. In contrast, the non-pigmented ciliary epithelium was positive for vimentin only.In the rat conjunctiva distributed goblet cell clusters were selectively stained with cytokeratin 7, 8, 18 and 19 specific monoclonal antibodies. Among them a group of cytokeratin 8 and 18 specific monoclonal antibodies which stained the goblet cells as well as cytokeratin 8 and 18 positive internal controls did not react with either the cytokeratin 8 and 18 positive neuroectodermal cells of the rat eye nor the rat choroid plexus epithelium. This indicates differences in the phenotype e.g. conformational epitope changes, of neuroectodermal derived and other cytokeratins. The corneal and conjunctival epithelium showed a more complex distribution of squamous epithelium type cytokeratins. The limbal region as a transient zone connecting both epithelia exhibited a changing cytokeratin pattern. In general, the study emphasized the necessity to work with an enlarged antibody panel to avoid misleading results in the immunolocalization of cytokeratins.Dedicated to Prof. Dr. H.J. Scharf (Halle, FRG) on the occasion of his 70th birthday     

Intermediate filament cytoskeleton of amnion epithelium and cultured amnion epithelial cells: expression of epidermal cytokeratins in cells of a simple epithelium

Using immunofluorescence microscopy and two-dimensional gel electrophoresis, we compared the cytoskeletal proteins expressed by human amnion epithelium in situ, obtained from pregnancies of from 10-wk to birth, with the corresponding proteins from cultured amnion epithelial cells and cultures of cells from the amniotic fluid of 16 week pregnancies. Epithelia of week 16 fetuses already display tissue-specific patterns of cytokeratin polypeptides which are similar, although not identical, to those of the corresponding adult tissues. In the case of the simple amnion epithelium, a complex and characteristic complement of cytokeratin polypeptides of Mr 58,000 (No. 5), 56,000 (No. 6), 54,000 (No. 7), 52,500 (No. 8), 50,000 (No. 14), 46,000 (No. 17), 45,000 (No. 18), and 40,000 (No. 19) is present by week 10 of pregnancy and is essentially maintained until birth, with the addition of cytokeratin No. 4 (Mr 59,000) and the disappearance of No. 7 (Mr 54,000) at week 16 of pregnancy. In full-term placentae, the amnion epithelium displays two morphologically distinct regions, i.e., a simple and a stratified epithelium, both of which express the typical amnion cytokeratin polypeptides. However, in addition the stratified epithelium also synthesizes large amounts of special epidermal cytokeratins such as No. 1 (Mr 68,000), 10 (Mr 56,500), and 11 (Mr 56,000). In culture amnion epithelial cells obtained from either 16-wk pregnancies or full-term placentae will continue to synthesize the amnion-typical cytokeratin pattern, except for a loss of detection of component No. 4. This pattern is considerably different from the cytokeratins synthesized by cultures of cells from amniotic fluids (cytokeratins No. 7, 8, 18, and 19, sometimes with trace amounts of No. 17) and from several so-called "amnion epithelial cell lines." In addition, amnion epithelial cells in situ as well as amnion epithelial cell cultures appear to be heterogeneous in that they possess some cells that co-express cytokeratins and vimentin. These observations lead to several important conclusions: In contrast to the general concept of recent literature, positively charged cytokeratins of the group No. 4-6 can be synthesized in a simple, i.e., one-layered epithelium. The change from simple to stratified amnion epithelium does not require a cessation of synthesis of cytokeratins of the simple epithelium type, but in this case keratins characteristic of the terminally differentiated epidermis (No. 1, 10, and 11) are also synthesized.(ABSTRACT TRUNCATED AT 400 WORDS)     

Heterogeneity in the immunolocalization of cytokeratin-specific monoclonal antibodies in the rat lung: evaluation of three different alveolar epithelial cell types

The distribution of individual cytokeratin polypeptides in the adult rat lung parenchyma was investigated by immunohistochemistry with 44 monoclonal and 2 polyclonal antibodies. Simple epithelial cytokeratins 7, 8, 18 and 19 were found to be expressed differently in alveolar and bronchial epithelial cells. Three distinct types of alveolar cells were detected according to their pattern of immunoreactivity: type II cells strongly expressing cytokeratins 8 and 18 and weakly expressing cytokeratins 7 and 19 in the cell periphery; type I cells predominantly positive for cytokeratins 7 and 19 and weakly for cytokeratin 8; and a newly defined third cell type III (alveolar brush cell) with cytokeratin 18 abundantly expressed but organized in an unusual intracellular (globular) structure. The latter cell type failed to bind the type II specific Maclura pomifera lectin, and contained no surfactant proteins. Bronchial epithelial cells exhibited a more or less uniform staining pattern for cytokeratins 8, 18 and 19 and focally for cytokeratins 4 and 7.This work was supported by Bundesminister für Forschung und Technologie (07NBL03) and Dakopatts (Glostrup, Denmark)     

Cytokeratin polypeptide patterns of different epithelia of the human male urogenital tract: immunofluorescence and gel electrophoretic studies

Intermediate filament proteins of normal epithelia of the human and the bovine male urogenital tract and of certain human renal and bladder carcinomas have been studied by immunofluorescence microscopy and by two-dimensional gel electrophoresis of cytoskeletal fractions from microdissected tissue samples. The patterns of expression of cytokeratin polypeptides differ in the various epithelia. Filaments of a cytokeratin nature have been identified in all true epithelial cells of the male urogenital tract, including renal tubules and rete testis. Simple epithelia of renal tubules and collecting ducts of kidney, as well as rete testis, express only cytokeratin polypeptides nos. 7, 8, 18, and 19. In contrast, the transitional epithelia of renal pelvis, ureter, bladder, and proximal urethra contain, in addition to those polypeptides, cytokeratin no. 13 and small amounts of nos. 4 and 5. Most epithelia lining the human male reproductive tract, including those in the epididymis, ductus deferens, prostate gland, and seminal vesicle, synthesize cytokeratin no. 5 in addition to cytokeratins nos. 7, 8, 18, and 19 (cytokeratin no. 7 had not been detected in the prostate gland). Cytokeratin no. 17 has also been identified, but in very low amounts, in seminal vesicle and epididymis. The cytokeratin patterns of the urethra correspond to the gradual transition of the pseudostratified epithelium of the pars spongiosa (cytokeratins nos. 4, 5, 6, 13, 14, 15, and 19) to the stratified squamous epithelium of the fossa navicularis (cytokeratins nos. 5, 6, 10/11, 13, 15, and 19, and minor amounts of nos. 1 and 14). The noncornified stratified squamous epithelium of the glans penis synthesizes cytokeratin nos. 1, 5, 6, 10/11, 13, 14, 15, and 19. In immunofluorescence microscopy, selective cytokeratin antibodies reveal differential staining of different groups or layers of cells in several epithelia that may relate to the specific expression of cytokeratin polypeptides. Human renal cell carcinomas show a simple cytokeratin pattern consisting of cytokeratins nos. 8, 18, and 19, whereas transitional cell carcinomas of the bladder reveal additional cytokeratins such as nos. 5, 7, 13, and 17 in various proportions. The results shows that the wide spectrum of histological differentiation of the diverse epithelia present in the male urogenital tract is accompanied by pronounced changes in the expression of cytokeratin polypeptides and suggest that tumors from different regions of the urogenital tract may be distinguished by their cytokeratin complements.     

Detection of a cytokeratin determinant common to diverse epithelial cells by a broadly cross-reacting monoclonal antibody.

A monoclonal antibody derived from a mouse immunized with bovine epidermal prekeratin has been characterized by its binding to cytoskeletal polypeptides separated by one- or two-dimensional gel electrophoresis and by immunofluorescence microscopy. This antibody (KG 8.13) binds to a determinant present in a large number of human cytokeratin polypeptides, notably some polypeptides (Nos. 1, 5, 6, 7, and 8) of the 'basic cytokeratin subfamily' defined by peptide mapping, as well as a few acidic cytokeratins such as the epidermis-specific cytokeratins Nos. 10 and 11 and the more widespread cytokeratin No. 18. This antibody reacts specifically with a wide variety of epithelial tissues and cultured epithelial cells, in agreement with previous findings that at least one polypeptide of the basic cytokeratin subfamily is present in all normal and neoplastic epithelial cells so far examined. The antibody also reacts with corresponding cytokeratin polypeptides in a broad range of species including man, cow, chick, and amphibia but shows only limited reactivity with only a few rodent cytokeratins. The value of this broad-range monoclonal antibody, which apparently recognizes a stable cytokeratin determinant ubiquitous in human epithelia, for the immunohistochemical identification of epithelia and carcinomas is discussed.     

Variation and frequency of cytokeratin polypeptide patterns in human squamous non-keratinizing epithelium

The squamous non-keratinizing epithelium of the human upper digestive tract was analyzed for keratin-like cytoskeletal proteins (cytokeratins) by both high resolution one- and two-dimensional gel electrophoresis. The Triton/high salt-insoluble portion of pure epithelial homogenates contains a number of SDS- and urea-extractable polypeptides, whose two-dimensional gel pattern (NEpHG/SDS) typically represents a defined subset of human cytokeratins. The cytoskeletal preparations of epithelial tissue samples obtained from different individuals were found to be uniform with respect to their content of cytokeratin polypeptides 55.0 kD/basic, 52.0 kD/acidic, and 49.0 kD/acidic. However, we have observed that four basic members of apparent molecular weight 60.0, 59.0, 56.5, and 56.0 kD occur at an inconstant rate. Consequently, the cytokeratin polypeptide patterns appeared highly variable as a result of the presence of constant plus compositionally different subsets of inconstant members. From the analysis of cytoskeletal portions of more than 300 individual tissue samples we demonstrate eight different keratin-like polypeptide patterns including their frequencies and propose the existence of no more than nine. These, most probably, encompass all the possible inter-individual variations to which the cytokeratins of this type of epithelium will combine for forming intermediate-sized filaments in vivo. We furthermore hypothesize that the observed variation of cytokeratin patterns may reflect a polymorphism of genes coding for the variable keratin-like polypeptide members.     

Cytoskeleton in neuroectodermally derived epithelial and muscle cells of the human iris and ciliary body.

The cytoskeleton of epithelial and muscle cells of the human iris and ciliary body was analyzed by immunohistochemistry in three morphologically normal formalin-fixed, paraffin-embedded eyes and in 34 eyes containing a uveal melanoma. Both layers of the iris epithelium reacted with monoclonal antibodies (MAb) V9 and Vim 3B4 to vimentin, whereas the ciliary epithelia additionally reacted with MAb CAM 5.2, CK5, KS-B17.2, and CY-90, recognizing cytokeratins 8 and 18. The same cytokeratin MAb labeled the retinal pigment epithelium, which lacked vimentin. The muscle portion of the anterior iris epithelium, which forms the dilator muscle, as well as the sphincter and ciliary muscles, reacted with MAb DE-U-10 to desmin and 1A4 to alpha-smooth muscle actin. The dilator and ciliary muscles also reacted with V9 and Vim 3B4 to vimentin, and some dilator fibers were weakly immunopositive for cytokeratin 8 and 18 with CY-90 and CAM 5.2. The antigenic profile of iris and ciliary epithelia infiltrated by melanoma cells remained unchanged. The intraocular epithelia, which are developmentally related but differ in function, and the intraocular muscles, which differ in origin but are functionally related, have distinct cytoskeletal profiles and may provide insights into the functional significance of intermediate filament expression.