Characterization of two monoclonal antibodies in an immunohistochemical study of keratin 8 and 18 expression

Suspension culture promotes serosal mesothelial development in human intestinal organoids

Pluripotent-stem-cell-derived human intestinal organoids (HIOs) model some aspects of intestinal development and disease, but current culture methods do not fully recapitulate the diverse cell types and complex organization of the human intestine and are reliant on 3D extracellular matrix or hydrogel systems, which limit experimental control and translational potential for regenerative medicine. We describe suspension culture as a simple, low-maintenance method for culturing HIOs and for promoting in vitro differentiation of an organized serosal mesothelial layer that is similar to primary human intestinal serosal mesothelium based on single-cell RNA sequencing and histological analysis. Functionally, HIO serosal mesothelium has the capacity to differentiate into smooth-muscle-like cells and exhibits fibrinolytic activity. An inhibitor screen identifies Hedgehog and WNT signaling as regulators of human serosal mesothelial differentiation. Collectively, suspension HIOs represent a three-dimensional model to study the human serosal mesothelium.

The serosal mesothelium is a major source of smooth muscle cells of the gut vasculature

Most internal organs are situated in a coelomic cavity and are covered by a mesothelium. During heart development, epicardial cells (a mesothelium) move to and over the heart, undergo epithelial-mesenchymal transition (EMT), and subsequently differentiate into endothelial and vascular smooth muscle cells. This is thought to be a unique process in blood vessel formation. Still,structural and developmental similarities between the heart and gut led us to test the hypothesis that a conserved or related mechanism may regulate blood vessel development to the gut, which, similar to the heart, is housed in a coelomic cavity. By using a combination of molecular genetics, vital dye fate mapping, organ culture and immunohistochemistry, we demonstrate that the serosal mesothelium is the major source of vasculogenic cells in developing mouse gut. Our studies show that the gut is initially devoid of a mesothelium but that serosal mesothelial cells expressing the Wilm's tumor protein (Wt1)move to and over the gut. Subsequently, a subset of these cells undergoes EMT and migrates throughout the gut. Using Wt1-Cre genetic lineage marking of serosal cells and their progeny, we demonstrate that these cells differentiate to smooth muscle of all major blood vessels in the mesenteries and gut. Our data reveal a conserved mechanism in blood vessel formation to coelomic organs, and have major implications for our understanding of vertebrate organogenesis and vascular deficiencies of the gut.

Database on monoclonal antibodies to Cytokeratins

Cytokeratins (CK) are being extensively used as diagnostic markers for various malignancies and other diseases, including human oral precancer and cancer, due to their tissue specific expression. CK are epithelia specific intermediate filament (IF) proteins, which are expressed in a differentiation dependent and tissue specific manner. There are about 30 polypeptides of CK expressed by different human epithelia. Each type of epithelium expresses about 4-6 polypeptides. CK polypeptides share many common epitopes, due to which the antibodies developed against CK tend to cross react. Therefore, a large number of monoclonal and polyclonal antibodies have been developed to distinguish among these proteins. Many of these antibodies are not only monospecific but are also epitope specific. These antibodies are being used in pathology laboratories for routine diagnosis using immunohistochemistry. A number of fixatives are used for fixation of tissue sections prior to the use of these antibodies. Sometimes, this leads in epitope masking. Hence, it becomes necessary to use a battery of monoclonal antibodies (MAb) for accurate diagnosis. Apart from the use of these antibodies in diagnostics, they are also being used in basic research for the study of CK function and their interactions with associated proteins and membrane proteins. In the present communication an effort has been made to make a comprehensive list of MAb to CK giving information like cross-reactivity, epitope specificity, various fixatives used, etc. along with the source of the antibodies, which will provide useful information to the users.

KM195 as an immunohistochemical marker of adenocarcinoma of the lung

In order to improve the diagnosis of lung carcinoma, in which a complicated histologic pattern is present, the immunohistochemistry of 119 adenocarcinomas, 65 squamous cell carcinomas, 12 small cell carcinomas, 18 large cell carcinomas, and 15 metastatic adenocarcinoma in the lung were evaluated using a monoclonal antibody, KM195, against lung carcinoma, and compared with the immunohistochemical results using anti-human cytokeratin (CAM 5.2) and other monoclonal antibodies. Formalin-fixed, paraffin-embedded tissues were stained using the labeled streptavidin-biotin method. Extracts from fresh tissue homogenate, after fractionation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were transferred by Western blotting and stained with KM195. The anti-lung adenocarcinoma, murine, monoclonal antibody KM195 (IgG), was positive in 107 of 119 adenocarcinomas (90%), in 15 of 18 large cell carcinoma (83%), in three of 65 squamous cell carcinomas (5%), 13 of 15 (87%) metastatic adenocarcinoma in the lung, and was negative in 12 small cell carcinomas (P < 0.001). KM195-bound protein of primary and metastatic adenocarcinoma in the lung cases concentrated at about 40 kDa. In contrast, CAM 5.2 was positive in 52 of 67 (78%) adenocarcinomas, 10 of 62 (16%) squamous cell carcinomas, and was negative in six small cell carcinomas. These results suggest that the immunohistochemistry for KM195 may be a more useful marker over CAM 5.2 for the diagnosis of pulmonary adenocarcinoma.

Immunohistochemical reactivity of basal and luminal epithelium-specific cytokeratin antibodies within normal and neoplastic canine mammary glands

Human basal epithelium (myoepithelium)-specific (312C8-1) and luminal epithelium-specific (13H5) cytokeratin antibodies were applied to frozen sections of normal canine mammary tissues (seven), benign adenomas and hyperplasias (five), mixed tumors (12), and adenocarcinomas (18) to determine if epithelial subsets could be discriminated by the use of an avidin biotin peroxidase complex immunohistochemical procedure. The 312C8-1 and 13H5 antibodies were consistently reactive with basal and luminal epithelium, respectively, in the normal mammary gland (7/7) and in benign adenomas and hyperplasias (5/5). Mixed mammary tumors had similar basal and luminal epithelial reactivity and also had proliferating spindle-shaped stromal cells that were reactive with 312C8-1 (10/12) and 13H5 (4/12). The adenocarcinomas were subclassified into basal, luminal, and basal/luminal on the basis of 312C8-1 reactivity (4/18), 13H5 reactivity (2/18), and dual reactivity with mutually exclusive anatomic distribution (11/18), respectively. Those tumors with dual immunoreactivity were indicative of noninvasive carcinomas. Dogs with neoplasms that were reactive with 312C8-1 and nonreactive with 13H5 had local recurrence or distant metastasis within 2 weeks to 6 months after diagnosis. Other antibodies used for comparison were pan cytokeratin AE1/AE3, actin HHF35, and vimentin. 312C8-1 and 13H5 antibodies are specific for canine mammary basal and luminal epithelium, respectively, and by employing these antibodies, the origin and differentiation of canine mammary neoplasms can be determined more accurately than on the basis of hematoxylin and eosin-stained tissue alone.

Changes in cytokeratin expression during the development of the human oral mucosa

The changes in cytokeratin expression by the developing oral mucosa of 10 to 23-week-old human fetuses were studied by indirect immunofluorescence using a panel of 15 monoclonal antibodies. The lining and masticatory mucosae were incompletely differentiated in 10-wk fetuses, since they expressed identical patterns of cytokeratins (CK 4, 5, 8, 13, 18, 19 and probably CK 14, 16, 17) very similar to that of adult alveolar mucosa. The main difference was the presence of cytokeratins 8, 18 and 19 in embryonic tissues. Cytokeratins 1, 2, 10 and 11 began to appear in gingival and hard palate epithelium from wk 11, predicting the differentiation of the masticatory mucosa by wk 16. The patterns of cytokeratin expression in the 23-wk fetus in the lining and masticatory mucosae appear to be different. In lining mucosa, the only difference from the 10th wk is a decrease in cytokeratins 8, 18 and 19, whereas the pattern of cytokeratin expression in masticatory mucosa (CK 1, 2, 4, 5, 8, 10, 11, 13, 18, 19 and probably CK 14, 16 and 17) is now very near that of adult gingiva. This pattern appears, as in the adult, to be similar to that of the epidermis in the same period.

Marjolin's ulcer: immunohistochemical study of 17 cases and comparison with common squamous cell carcinoma and basal cell carcinoma

Formalin-fixed, paraffin-embedded biopsy specimens of 17 cases of squamous cell carcinoma of Marjolin's ulcer (SCC-MU), 6 cases of common SCC (SCC), and 5 cases of basal cell carcinoma (BCC) were stained with three monoclonal antikeratin antibodies (CAM 5.2, MAK-6, and MA-903), a monoclonal antivimentin antibody (V9), and a polyclonal anticarcinoembryonic antigen antiserum (A115). Neoplastic cells of SCC-MU, SCC, and BCC showed consistently negative staining for CAM 5.2. A wide range of reactivity, from negative to diffuse strong positivity, among neoplastic cells of SCC-MU and SCC was noted with MAK-6. Alternatively, neoplastic cells of SCC-MU, SCC, and BCC consistently showed diffuse moderate to strong reactivity with MA-903. These findings imply that SCC-MU has largely high-molecular-weight keratins. They also showed a wide range of reactivity with V9. However, neoplastic cells of five of the six SCC and five cases of BCC were negative for V9. These findings suggest that neoplastic cells of SCC-MU contain vimentin in higher frequency than in the more usual SCC.

Cytokeratin expression in adrenocortical neoplasia: An immunohistochemical and biochemical study with implications for the differential diagnosis of adrenocortical, hepatocellular, and renal cell carcinoma

The immunostaining patterns of adrenocortical tumors are not clearly defined, primarily due to their inconsistent expression of cytokeratins (CK). To address this issue and to investigate whether adrenocortical tumors can be immunohistochemically differentiated from histologically similar tumors arising from the kidney and liver, we studied four normal adrenal glands, two adrenocortical adenomas (ACAs), 31 adrenocortical carcinomas (ACCs), 37 renal cell carcinomas (RCCs), and 33 hepatocellular carcinomas (HCCs) with anti-CK antibodies AE1, CAM 5.2, UCD/PR10.11, 35BH11, PKK1, and Ks19.1, as well as antibodies to vimentin (VIM), epithelial membrane antigen (EMA), and HMFG-2. Normal adrenal cortical cells showed variable staining with all anti-CK antibodies on fixed and frozen sections. In contrast, only one of two fixed ACAs stained with a single anti-CK, although both neoplasms reacted with multiple anti-CK antibodies on frozen sections. Similarly, 20 of 31 fixed ACCs contained VIM, but only one tumor stained for CK; frozen sections of this and another, previously negative tumor, however, stained with most of the anti-CK antibodies tested. One-dimensional Western immunoblot analysis confirmed the presence of CKs 18 and 19 in two examples of normal adrenal cortex, one ACA, and the ACC immunohistochemically positive on fixed and frozen sections, with CK 19 identified in the ACC that was positive on frozen section alone. All fixed HCCs and most RCCs stained with multiple anti-CK antibodies (33 and 34 cases, respectively), with a proportion of tumors positive for VIM (six and 22 cases, respectively), EMA (seven and 30 cases, respectively), and HMFG-2 (15 and 28 cases, respectively). The results suggest that CK expression is diminished in most adrenocortical tumors to levels too low to be recognized following the deleterious effects of fixation. While the immunohistochemical absence of CK, EMA, and HMFG-2 in fixed sections in the majority of ACCs is distinctive, sufficient phenotypic overlap exists such that differentiation between RCC and HCC may not be possible in an individual case.

Changes of cytokeratin filament organization in human and murine Mallory body-containing livers as revealed by a panel of monoclonal antibodies

Mallory bodies (MBs) are characteristics morphologic features of alcoholic hepatitis and can be produced in mouse hepatocytes by chronic griseofulvin (GF) intoxication. The formation of MBs, which share some immunological, biochemical, and ultrastructural features with cytokeratin (CK) filaments of normal liver, is accompanied by derangement and even loss of the CK cytoskeleton of hepatocytes ("empty cells") as revealed by immunofluorescence microscopy. To clarify whether this diminution or lack of CK-related staining of MB-containing hepatocytes was due to loss of CK filaments or changes in antigenicity or accessibility of antigenic determinants immunohistochemical studies using a battery of monoclonal and polyclonal CK antibodies were performed. It could be shown that all these antibodies directed against different CK polypeptide components and antigenic determinants of CKs revealed a highly reduced or even undetectable cytoplasmic CK meshwork in most cells with fully developed large MBs. In the light of our present knowledge of the organization of CK intermediate filaments, these results indicate that the phenomenon of the "empty cells" reflects a diminution of CK meshwork rather than altered antigenic determinants.

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.

Cytokeratin-immunoreactive cells of human lymph nodes and spleen in normal and pathological conditions. An immunocytochemical study

The occurrence and the distribution of cytokeratin (CK)-immunoreactive reticulum cells in a series of normal and pathological human lymph nodes and spleens are documented. The immunoreactive cells exhibit morphological and immunophenotypic features of so-called fibroblastic reticulum cells, with or without myoid differentiation. They invariably co-express vimentin and, to a lesser extent, desmin and muscle-specific actin isoforms. These CK-immunoreactive cells are apparently a normal subpopulation of reticulum cells, being detectable from the early stages of spleen and lymph node development. They are distributed mainly in the paracortical and medullary regions of the lymph nodes and at the periphery of the white pulp in the spleen. Their number and distribution are highly variable in different neoplastic and non-neoplastic pathological conditions but the changes are not disease specific. CK-immunoreactive reticulum cells are easily identifiable in both frozen and fixed lymphoid tissue and in cytological smears of fine-needle aspirates, provided that monoclonal antibodies whose spectrum of reactivity includes cytokeratins 8 and 18 are used. The awareness of the occurrence of CK-immunoreactive cells in normal lymphoid tissues is of particular relevance in the search for micrometastatic foci using anti-CK antibodies.

Keratin protein expression during the development of conducting airway epithelium in nonhuman primates

Keratin protein expression during the development of Rhesus monkey conducting airway epithelium was investigated by both biochemical and immunohistochemical methods. Keratin proteins were extracted from tracheal and intrapulmonary airway tissues of fetal (at 80- and 140-day gestational ages), neonatal, and adult animals. Using immunoblot analyses and immunohistochemistry with various monoclonal (AE1, AE3, AE8, 6.01 and 6.11) and monospecific antibodies (anti-50/55 and anti-40 kDa), the presence of keratins 5, 6, 8, 13, 14, and 19 in adult airway epithelium were demonstrated. Except for keratin 13 (51 kDa), the remaining keratins could be immunologically detected in fetal and neonatal tissues. To further understand the nature of the synthesis of keratin 13 during development, airway epithelial cells from different ages were isolated and cultured in vitro. Cultured cells were labeled with 35S-methionine, and the patterns of keratin protein were analyzed by one- and two-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Results indicated that the cultured airway cells synthesized additional keratins including 7, 15, 16, 17, and 18. However, consistent with the in vivo finding, fetal cells synthesized less or no keratin 13. These in vivo and in vitro studies strongly suggest that the synthesis of the keratin 13 in monkey conducting airway epithelium is developmentally regulated.