Immunochemical characterization of mucins. Polypeptide (M1) and polysaccharide (A and Leb) antigens

Increase in genogroup II.4 norovirus host spectrum by CagA-positive Helicobacter pylori infection

BACKGROUND

Noroviruses (NoVs) represent a considerable public health burden. Despite their enormous genetic diversity, most outbreaks are due to the single GII.4 genotype, but the reasons for this are poorly understood. NoVs use histo-blood group antigens (HBGAs) as attachment factors. Since HBGAs are present in saliva, binding of strains to saliva is commonly used as a surrogate for recognition of the gut surface by specific strains, although the relationship between saliva and gut tissue expression of HBGAs is not well defined.

METHODS

The presence of fucosylated HBGAs in saliva and stomach biopsy specimens, as well as that of genogroup I.1 and genogroup II.4 virus-like particles, were compared in a series of 109 donors from Portugal.

RESULTS

An overall good concordance between HBGA expression in saliva and stomach surface mucosa was observed. However, unexpected mucosal expression of α(1,2)fucosylated epitopes in nonsecretor individuals was frequently detected, allowing for GII.4 attachment. Although all individuals were infected with Helicobacter pylori, abnormal expression of α(1,2)fucosylated motifs and binding of GII.4 virus-like particles in nonsecretors' mucosa were associated with positivity for the H. pylori CagA virulence factor.

CONCLUSIONS

Infection by CagA-positive H. pylori induces expression of GII.4 attachment factors in nonsecretors' mucosa, expanding the host range of these strains and thereby possibly contributing to their epidemiological dominance.

A 40-50kDa Glycoprotein Associated with Mucus is Identified as α-1-Acid Glycoprotein in Carcinoma of the Stomach

Background and Aim: Secreted gastric mucins are large O-glycosylated proteins of crude mucus gels which are aberrantly expressed in malignancy. An albumin associated 55-65kDa glycoprotein was previously shown in mucus gels in gastric cancer. The aim of this study was to investigate its expression and identification in human gastric tissue. Methods: Mucins were purified from crude mucus scrapings of 16 partial and 11 total resections and a rabbit polyclonal antibody was raised to the 55-65kDa glycoprotein. The location and expression of the glycoprotein was examined in normal gastric mucosa (n=20), intestinal metaplasia (n=18) and gastric cancer (n=27) tissue by immunohistochemistry. Mucins were analyzed by isoelectric focusing (IEF) on 2-D polyacrylamide gels. Identification of the 40-50kDa glycoprotein was by MALDI-TOF MS technique. Plasma levels were examined by Western blotting. Results: Extensive SDS-PAGE analysis gave a PAS positive glycoprotein in the 40-50kDa range, in patients with gastric cancer but not normals. It was expressed in parietal and columnar cells of normal gastric tissue and intestinal metaplasia respectively, and in 22 of 27 gastric cancer specimens. In 2-D PAGE stained with Coomassie Blue there were 3 spots positively identified as alpha-1-acid glycoprotein (AGP) by MALDI-TOF MS technique. PAS staining revealed a single bright spot in the same position but could not be identified. Preliminary measurements showed slightly higher levels of AGP in plasma of patients with gastric carcinoma. Conclusion: AGP levels are increased in gastric tissue and in the plasma of those with carcinoma of the stomach.

Development of a serum biomarker assay that differentiates tumor-associated MUC5AC (NPC-1C ANTIGEN) from normal MUC5AC

A serum ELISA using a monoclonal antibody that detects a MUC5AC-related antigen (NPC-1C antigen) expressed by pancreatic and colorectal cancer was developed. The NPC-1C antibody reacts with specific epitopes expressed by tumor-associated MUC5AC that does not appear on MUC5AC from normal tissues. Based on observations of a highly specific antibody, we tested the ELISA to differentiate serum from healthy blood donors compared to serum from patients with colorectal or pancreatic cancer. Additionally, patient tumor tissue was stained to examine the expression pattern of MUC5AC-related antigen in pancreatic and colorectal cancers. The results indicate the NPC-1C antibody ELISA distinguished serum of cancer patients from normal donors with very good sensitivity and specificity. Most patient's tumor biopsy exhibited NPC-1C antibody reactivity, indicating that tumor-associated MUC5AC antigen from tumor is shed into blood, where it can be detected by the NPC-1C antibody ELISA. This serum test provides a new tool to aid in the diagnosis of these cancers and immune monitoring of cancer treatment regimens.

Proteases present in some pancreatic cyst fluids may affect mucin immunoassay by degrading antibodies and antigens

OBJECTIVES

Biomarker detection in pancreatic cyst fluids is of importance to improve the diagnosis of mucinous cystadenoma, a precancerous lesion. However, assay protocols are generally established for serum testing.

METHODS

Immunoradiometric assay of gastric M1/MUC5AC mucin was performed on pancreatic cyst fluids with well-characterized monoclonal antibodies.

RESULTS

Among 1466 pancreatic cyst fluids tested, about 10% to 15% of samples presented abnormal behaviors: (i) radioactivity measured after immunoradiometric assay much lower than the blank of the assay and (ii) increasing dilution of the fluids leading to apparent increase of M1/MUC5AC concentration. In contrast, none of the 109 hepatic cyst fluids tested presented interference.We demonstrate that some (n = 54) interfering fluids cause mucin degradation as well as antibody degradation. Western blot analysis showed that the C-terminal part of the M1/MUC5AC apomucin is most sensitive to degradation.

CONCLUSIONS

The presence of proteases that degrade antibodies as well as mucin may explain the pitfalls observed in 3.6% of the samples. To detect this interference, each fluid has to be systematically tested at 1:100 dilution in the presence of a saturating concentration of M1/MUC5AC mucin standard and in the absence of antiprotease reagents. Detection of interference could prevent false results caused by mucin degradation in situ.

The carbohydrate moiety and high molecular weight carrier of histo-blood group antigens are both required for norovirus-receptor recognition

Histo-blood group antigens (HBGAs) on human intestinal epithelium serve as receptors for noroviruses (NVs). These antigens also are expressed in milk and may act as decoy receptors to protect breast-fed infants and others against NV disease. In this study we demonstrated that human milk is highly variable in synthesis of HBGAs, which differs from that of saliva; a large quantity of small, soluble HBGAs are found in milk, but much less in saliva and are recognized by MAbs, but not by NVs. There is another group of HBGAs, of high MW, found in both milk and saliva, and recognized by both NVs and MAbs. These results suggest that the specificity of NVs and MAbs to HBGAs are different and the backbones in addition to the carbohydrate moiety are required for NV recognition. Further studies to define the structure and genetics of the high MW milk glycans are necessary.

Inhibition of the interaction between the SARS-CoV spike protein and its cellular receptor by anti-histo-blood group antibodies

Severe acute respiratory syndrome coronavirus (SARS-CoV) is a highly pathogenic emergent virus which replicates in cells that can express ABH histo-blood group antigens. The heavily glycosylated SARS-CoV spike (S) protein binds to angiotensin-converting enzyme 2 which serves as a cellular receptor. Epidemiological analysis of a hospital outbreak in Hong Kong revealed that blood group O was associated with a low risk of infection. In this study, we used a cellular model of adhesion to investigate whether natural antibodies of the ABO system could block the S protein and angiotensin-converting enzyme 2 interaction. To this aim, a C-terminally EGFP-tagged S protein was expressed in chinese hamster ovary cells cotransfected with an α1,2-fucosyltransferase and an A-transferase in order to coexpress the S glycoprotein ectodomain and the A antigen at the cell surface. We observed that the S protein/angiotensin-converting enzyme 2-dependent adhesion of these cells to an angiotensin-converting enzyme 2 expressing cell line was specifically inhibited by either a monoclonal or human natural anti-A antibodies, indicating that these antibodies may block the interaction between the virus and its receptor, thereby providing protection. In order to more fully appreciate the potential effect of the ABO polymorphism on the epidemiology of SARS, we built a mathematical model of the virus transmission dynamics that takes into account the protective effect of ABO natural antibodies. The model indicated that the ABO polymorphism could contribute to substantially reduce the virus transmission, affecting both the number of infected individuals and the kinetics of the epidemic.

Expression of conserved mucin domains by epithelial tissues in various mammalian species

Mucins are related to infectious and non-infectious diseases in Veterinary and Human Medicine. MUC1 mucin is a transmembrane glycoprotein expressed on the apical surface of human epithelia while MUC5AC is the predominant secreted mucin expressed in human gastric epithelium and goblet cells of lung and eyes. MUC5AC C-terminus cysteine rich regions and the cytoplasmic tail of MUC1 domains are conserved among several mammalian species.

OBJECTIVE

to compare the expression of MUC1 and MUC5AC mucins in mammalian epithelia. CT33 anti-MUC1 cytoplasmic tail (MUC1CT) polyclonal antibody and 45M1 anti-MUC5AC monoclonal antibody were employed. By immunohistochemistry, MUC1CT was expressed in most tissues while MUC5AC was restricted to gastric surface epithelium and goblet cells from trachea and lung. By western blot, MUC1CT showed a band at approximately 35 kDa in most tissues; MUC5AC revealed bands at >180 kDa in stomach and lung secretions from rat, cat, pig and cow. When rat MUC5AC was immunoprecipitated, a band at about 180 kDa was obtained.

Abnormal expression of M1/MUC5AC mucin in distal colon of patients with diverticulitis, ulcerative colitis and cancer

The abnormal expression of gastric M1/MUC5AC mucin in precancerous lesions and colon cancer evidenced by immunohistochemistry led us to check for its presence in the mucus obtained directly from patients undergoing surgery for cancerous (adenocarcinoma) or inflammatory (diverticulitis or ulcerative colitis) diseases. In parallel, the authors quantified aberrant crypt foci (ACF) and their immunolabelling by M1/MUC5AC in mucosae of cancer and diverticulitis patients. Immuno-Radio-Metric Assay of M1/MUC5AC mucin developed by the authors was used to detect M1/MUC5AC mucin in the colonic mucus scraped from surgical specimens. M1/MUC5AC mucin was detected in the mucus of 51/69 (74%) patients with colon adenocarcinoma, versus 7/27 (26%) patients with diverticulitis (threshold: 30 units of M1 mucin per mg protein, area under ROC curve: 0.80). M1/MUC5AC was present in significantly (p < 0.001) larger amounts in the mucus of cancer versus diverticulitis patients. All (10/10) patients with ulcerative colitis tested showed levels above the threshold and their mucosae were strongly labelled with the anti-M1/MUC5AC antibody by immunohistochemistry. Patients with cancer exhibited 3 fold more ACF than those with diverticulitis, but no significant difference was observed in the mean size and M1/MUC5AC expression pattern of ACF between these two groups. The expression of M1/MUC5AC was in correlation with their size. In macroscopically normal mucosa, ACF were the most important source of M1/MUC5AC mucin. Testing of M1/MUC5AC can enhance the detection of precancerous lesions and colon cancer.

PAR-2 activation increases human intestinal mucin secretion through EGFR transactivation

PAR-2 (protease-activated receptors-2) are G protein-coupled receptors whose action on mucin secretion by intestinal epithelial cells is still unknown. The aim of this study was to examine the effect of PAR-2 activation on mucin secretion in the human colonic goblet cell line HT29-Cl.16E and the intracellular pathways involved. We found that PAR-2 mRNA was constitutively expressed by HT29-Cl.16E cells as well as by isolated human normal colonocytes. The PAR-2-activating peptide SLIGKV-NH(2) elicited rapid mucin secretion in HT29-Cl.16E, which was partially inhibited by calcium chelator BAPTA. Inhibitors of MAPK activation (PD98059) and EGFR tyrosine kinase activity (AG1478) abrogated PAR-2-induced ERK1/2 and EGFR tyrosine phosphorylation, respectively, and subsequent mucin secretion. Finally, PAR-2-induced EGFR transactivation was involved upstream of ERK1/2 activation. Our results show that the activation of PAR-2 expressed by human intestinal epithelial cells enhances mucin secretion, a component of the intestinal innate defence, via a pathway involving EGFR transactivation.

Blood group related antigens in ocular cicatricial pemphigoid

AIM

To study the MUC5AC and the blood group related antigen expression in ocular cicatricial pemphigoid (OCP) according to the distribution of Lewis and secretor phenotypes in OCP patients compared to normal subjects.

METHODS

Immunostaining was performed on conjunctival biopsy specimens from 22 consecutive patients suffering from OCP, using monoclonal antibodies (Mabs) directed against the peptidic core MUC5AC mucin (anti-M1/MUC5AC Mabs) and against the saccharide moieties (anti-blood group related antigens). These latter included anti-Le(a), anti-Le(b), anti-sialyl Le(a), and H type 2 Mabs, which immunoreact with Lewis positive and non-secretor (Le(a)), Lewis positive and secretor (Le(b)), Lewis positive (sialyl Le(a)), and secretor (H type 2) phenotypes respectively. Serological tests were also performed to confirm the phenotype of each patient. The immunohistopathological patterns and the distribution of Lewis and secretor phenotypes were compared with the results of a previous study in normal individuals.

RESULTS

(1) In OCP patients compared to the normal population, anti-M1 immunoreactivity of goblet cells was unchanged, whereas anti-Le(a), anti-Le(b), and anti-sialyl Le(a) immunoreactivities of epithelial and/or goblet cells were markedly decreased. (2) 41% of OCP patients had a non-secretor phenotype, which is statistically significantly more than the estimated incidence of the same phenotype in the French population (20%) (p approximately 0.04).

CONCLUSIONS

Mucins in OCP patients showed a decreased expression of blood group related antigens whereas the MUC5AC peptidic core detected by anti-M1 Mab remained unchanged. These results also seem to indicate that OCP may be associated with a non-secretor phenotype.

Macrocystic pancreatic cystadenoma: The role of EUS and cyst fluid analysis in distinguishing mucinous and serous lesions

BACKGROUND

Benign pancreatic serous cystadenoma usually is morphologically distinguishable from mucinous cystadenomas, which require resection because of their malignant potential. A macrocystic variant of serous cystadenoma recently has been described, rendering this important distinction more difficult. The aim of this study was to determine the EUS and tumor marker characteristics of mucinous cystadenoma compared with macrocystic serous cystadenomas.

METHODS

Medical records for consecutive patients seen between 1995 and 2002, with a histopathologic diagnosis of mucinous cystadenoma or macrocystic serous cystadenoma after surgery, who had undergone a detailed EUS examination, including EUS-guided FNA, were retrospectively reviewed.

RESULTS

A resection specimen was available for 32 mucinous cystadenomas and 9 macrocystic serous cystadenomas. No significant differences were observed with regard to clinical data (age, gender, presence of symptoms), lesion size, and location within the pancreas. All mucinous cystadenomas had a discernible cyst wall (thickened, 66%; focal parietal nodules, 25%) compared with 56% of macrocystic serous cystadenomas (p<0.0001). A thick echo content also was more frequent in mucinous cystadenoma (56% vs. 11%; p=0.04; statistical significance removed by the Bonferroni correction). Microcysts were only observed in macrocystic serous cystadenomas (44%; p=0.0008). The combination of a cyst wall that is thickened and the absence of microcysts had a sensitivity of 100% and specificity of 78% for the diagnosis of mucinous cystadenoma compared with macrocystic serous cystadenoma. Although intracystic carbohydrate-associated antigen 72-4 and mucins M1 were non-discriminatory, low carcinoembryonic antigen (<5 ng/mL) and carbohydrate-associated antigen 19-9 (<50,000 U/mL) values were found in macrocystic serous lesions (respectively, 100% and 100%; p=0.0002 and p=0.0002).

CONCLUSIONS

Although there is considerable overlap, helpful EUS characteristics that differentiate mucinous cystadenoma from macrocystic serous cystadenoma include a thick cyst wall and microcysts. These features, coupled with analysis of aspirated fluid for tumor markers (especially carcinoembryonic antigen), should help to confirm the diagnosis.

Mapping of SOMU1 and M1 Epitopes on the Apomucin Encoded by the 5′ End of the MUC5AC Gene

We have developed 11 monoclonal antibodies (MAbs) against human gastric mucin, (1-13M1, 2-11M1, 2-12M1, 9-13M1, 58M1, 19M1, 21M1, 45M1, 463M, 589M, 62M1), which specifically stained by immunohistochemisty both the human gastric surface mucosa and colon adenoma. Among them, five (19M1, 21M1, 463M, 589M, 62M1) immunoreacted with the peptide encoded by the 3' region of the MUC5AC gene (Nollet et al: Int J Cancer 2002;99:336-343). In this study, we identified in the 5' region of this gene the nucleotide fragments encoding peptides immunoreacting with three other anti-M1 MAbs (1-13M1, 2-11M1 and 9-13M1), as well as the SOMU1 MAb (Sotozono et al: J Immunol Methods 1996;192:187-196). 1-13M1 MAb immunoreacts with peptides, including the Cys 2 and Cys 4 domains. The SOMU1 MAb recognized the Cys 5 domain, and the MAbs 2-11M1 and 9-13M1 the globular D1/D2 and D3 domains, respectively. Using serial sections of the mucosae adjacent to colon adenocarcinomas and colon adenomas, we observed that the anti-M1 and anti-SOMU1 MAbs displayed the same immunostaining patterns. The three anti-M1 MAbs (2-12M1, 58M1, and 45M1) did not react with the products of the MUC5AC gene tested until now. The MUC5AC apomucin is now well characterized by MAbs immunoreacting against seven different epitopes belonging to the different main cystein globular domains of this macromolecule. Such antibodies are useful tools for studying the biosynthesis, polymerization, and degradation of mucin.

Expression of histo-blood group A antigen increases resistance to apoptosis and facilitates escape from immune control of rat colon carcinoma cells

A and B histo-blood group antigens are present on carcinoma cells at the early stages of cancerogenesis and tend to disappear at later stages, but it is not yet clear whether they take part to the process of tumor progression. To gain some insight into this issue, we used a rat colon carcinoma experimental model. To obtain expression of the A antigen, REG cells were cotransfected with the rat A enzyme cDNA and a rat alpha1,2fucosyltransferase cDNA, either FTA or FTB, whereas PRO cells that spontaneously have alpha1,2fucosyltransferase activity were only transfected with the A enzyme cDNA. All A antigen-expressing transfected cells derived from either REG FTA, REG FTB, or PRO parental cells were more resistant to apoptosis induced by either serum deprivation or heat shock than were their respective controls. When injected to syngeneic immunocompetent rats, A enzyme-transfected PRO cells formed tumors that grew faster than those formed by mock-transfected PRO cells. However, in immunodeficient SCID mice, no difference in growth could be observed between the two types of tumors, indicating that the faster tumor growth of the A antigen-positive cells in immunocompetent animals was due to their higher ability to escape immune control and that this was associated with their higher degree of resistance to apoptosis. These results might explain the slightly augmented incidence of carcinomas observed in A and B blood group individuals compared to O individuals.

Activation of mucin exocytosis and upregulation of MUC genes in polarized human intestinal mucin-secreting cells by the thiol-activated exotoxin listeriolysin O

The secreted thiol-activated cytolysin listeriolysin O (LLO) was responsible for L. monocytogenes-induced high-molecular glycoproteins (HMGs) exocytosis in cultured human mucosecreting HT29-MTX cells. By biochemical analysis we demonstrate that the majority of secreted HMGs in LLO-stimulated cells are of mucin origin. In parallel, analysis of the expression of MUCs genes showed that the transcription of the MUC3, MUC4 and MUC12 genes encoding for membrane-bound mucins was increased in LLO-stimulated cells. Upregulation of the MUC3 gene correlates with an increased expression of the membrane-bound MUC3 mucin. In contrast, increase in secretion of the gel-forming MUC5AC mucin develops without upregulation of the MUC5AC gene. Finally, results showed that NF-kappaB and AP-1 transcription factors were not involved in LLO-induced upregulation of MUCs genes in HT29-MTX cells, whereas L. monocytogenes infection was able to promote the degradation of IkappaB proteins in the cells.

Cloning of a rat gene encoding the histo-blood group A enzyme. Tissue expression of the gene and of the A and B antigens

The complete coding sequence of a BDIX rat gene homologous to the human ABO gene was determined. Identification of the exon-intron boundaries, obtained by comparison of the coding sequence with rat genomic sequences from data banks, revealed that the rat gene structure is identical to that of the human ABO gene. It localizes to rat chromosome 3 (q11-q12), a region homologous to human 9q34. Phylogenetic analysis of a set of sequences available for the various members of the same gene family confirmed that the rat sequence belongs to the ABO gene cluster. The cDNA was transfected in CHO cells already stably transfected with an alpha1,2fucosyltransferase in order to express H oligosaccharide acceptors. Analysis of the transfectants by flow cytometry indicated that A but not B epitopes were synthesized. Direct assay of the enzyme activity using 2' fucosyllactose as acceptor confirmed the strong UDP-GalNAc:Fucalpha1,2GalalphaGalNAc transferase (Atransferase) activity of the enzyme product and allowed detection of a small UDP-Gal:Fucalpha1,2GalalphaGal transferase (B transferase) activity. The presence of the mRNA and of the A and B antigens was searched in various BDIX rat tissues. There was a general good concordance between the presence of the mRNA and that of the A antigen. Tissue distributions of the A and B antigens in the homozygous BDIX rat strain were largely different, indicating that these antigens cannot be synthesized by alleles of the same gene in this rat inbred strain.

Mapping of two new epitopes on the apomucin encoded by MUC5AC gene: expression in normal GI tract and colon tumors

Three hybridomas secreting monoclonal antibodies (MAbs) against human (62M MAb) or rat (463M and 589M MAbs) gastric mucins were isolated. These MAbs immunoreacted against a human recombinant protein encoded by the 3' region of the MUC5AC gene. We have mapped 2 new gastric mucin epitopes and the M1-f epitope previously characterized by the 19/21M1 MAbs on MUC5AC-encoded apomucin. The M1-f, 463/589M and 62M epitopes are located in the MUC11p15/von Willebrand factor (vWF)-A3uD4 domain, in the D4-(vWF)-like domain and in the C- and CK-vWF-like domains of MUC5AC, respectively. The 463/589M and 62M MAbs stained the surface epithelium of human gastric mucosae, but not the normal colon mucosae (except 463/589M MAbs, which immunoreacted with 5 of 49 cases). All hyperplastic polyps are stained strongly with the 463/589M MAbs and faintly with the 62M MAb. In addition, 463/589M epitope was detected in 64% of the adenomas and in 93% of the mucosae adjacent to adenocarcinomas; in contrast, only 9% of the adenomas and 29% of the mucosae adjacent to adenocarcinomas expressed the 62M epitope. The expression pattern of the 463/589M epitope in colonic carcinogenesis is different from that of the 19/21M1 epitope, although the 2 epitopes are encoded by MUC5AC gene.

EGTA treatment of human airways in vitro unmasks M1/MUC5AC mucin in submucosal glands

Mucin staining can be used to evaluate secretory activity of human airways. However, mucin epitopes may be masked by physicochemical properties of the secretions. The aim of this investigation was to examine the effects of the calcium chelator, ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) on the detection of M1/MUC5AC mucin in isolated human bronchial preparations. Immunohistochemical investigation and immunoradiometric assays with anti-M1 monoclonal antibodies (Mabs) were used to detect M1/MUC5AC mucin derived from bronchial preparations with an intact surface epithelium, or in tissues where the epithelium had been removed (rubbed preparations). The Mabs labelled both epithelial goblet cells and submucosal glandular cells in EGTA (4 mM)-exposed bronchial preparations, while only goblet cells were stained in EGTA (0.4 mM)-exposed tissues. The quantities of M1/MUC5AC mucin detected in either the bronchial fluids derived from EGTA (4 mM)-exposed intact and rubbed preparations or in bronchial fluids treated with EGTA (4 mM) were significantly increased by two-fold when compared with untreated control values (p<0.001). In addition, lactate dehydrogenase (LDH) activity and protein measurements were unaltered during exposure of human airways to EGTA (4 mM) suggesting that this treatment did not affect tissue viability. These results provide evidence that ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (4 mM) facilitates the detection of M1/MUC5AC mucin by altering the physicochemical properties of respiratory mucin, thereby exposing epitopes with which anti-M1 monoclonal antibodies are reactive. This will allow more accurate measurement of secretory activity in human airways in vitro.

MUC5AC mucin release from human airways in vitro: effects of indomethacin and Bay X1005

BACKGROUND

Increased secretion of mucus is a hallmark of many respiratory diseases and contributes significantly to the airflow limitation experienced by many patients. While the current pharmacological approach to reducing mucus and sputum production in patients is limited, clinical studies have suggested that drugs which inhibit the cyclooxygenase and/or 5-lipoxygenase enzymatic pathways may reduce secretory activity in patients with airway disease.

AIM

This study was performed to investigate the effects of indomethacin (cyclooxygenase inhibitor) and Bay x 1005 (5-lipoxygenase inhibitor) on MUC5AC release from human airways in vitro.

METHODS

An immunoradiometric assay was used to determine the quantities of MUC5AC present in the biological fluids derived from human airways in vitro. The measurements were made with a mixture of eight monoclonal antibodies (MAbs; PM8) of which the 21 M1 MAb recognized a recombinant M1 mucin partially encoded by the MUC5AC gene.

RESULTS

The quantities of MUC5AC detected in the biological fluids derived from human bronchial preparations were not modified after treatment with indomethacin (cyclooxygenase inhibitor) and/or an inhibitor of the 5-lipoxygenase metabolic pathway (BAY x 1005).

CONCLUSION

These results suggest that the cyclooxygenase and 5-lipoxygenase metabolic pathways play little or no role in the release of MUC5AC from human airways.

ATP induced MUC5AC release from human airways in vitro

BACKGROUND

Chronic airway diseases are often associated with marked mucus production, however, little is known about the regulation of secretory activity by locally released endogenous mediators.

AIM

This investigation was performed to determine the release of MUC5AC mucin from human bronchial preparations using the purinergic agonists adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP).

METHODS

Immunohistochemical and immunoradiometric assays (IRMA) were used to detect the MUC5AC mucin. Immunohistochemical analysis were performed using individual 1-13 M1 and 21 M1 MAbs recognizing a recombinant M1 mucin partially encoded by the MUC5AC gene. IRMA measurments were performed using a mixture of eight anti-M1 mucin MAbs (PM8), which included both 1-13 M1 and 21 M1 MAbs. Lysozyme and protein were also measured in the biological fluids derived from human bronchial preparations obtained from patients who had undergone surgery for lung carcinoma.

RESULTS

The anti-M1 monoclonal antibodies labelled epithelial goblet cells. After challenge of human bronchial preparations with ATP, the goblet cells exhibited less staining. In contrast, UTP did not alter the immunolabelling of goblet cells. MUC5AC mucin in the bronchial fluids derived from ATP-challenged preparations was increased while UTP had no effect on release. ATP did not alter either the quantities of lysozyme or protein detected in the biological fluids.

CONCLUSION

These results suggest that ATP may regulate epithelial goblet cell secretion of MUC5AC mucin from human airways in vitro.

Glycosylation alterations of cells in late phase apoptosis from colon carcinomas

Comparisons of carbohydrate profiles between control and apoptotic colon carcinoma cells were performed by flow cytometry using a set of lectins and anti-carbohydrate antibodies. The six cell lines analyzed presented distinct carbohydrate profiles before induction of apoptosis. PHA-L and MAA binding decreased after induction of apoptosis by UV-treatment. In contrast an increase of PNA binding was observed after induction of apoptosis, except on SW-48 cells for which a decrease occurred. A decrease of SNA binding was observed after induction of apoptosis from strongly positive control cell lines, whereas it increased on weakly positive ones. All the blood group related antigens A, H, Lewis a, Lewis x, Lewis b, and Lewis y, had their expression strongly diminished on apoptotic cells. These changes occurred irrespective of the mode of apoptosis induction since similar results were obtained after UV, TNFalpha, or anti-Fas treatment. Fucosyltransferases activities were also decreased after apoptosis induction, except for alpha1,3fucosyltransferase in anti-Fas treated HT-29 cells, where it was strongly augmented. This could be attributed to the IFNgamma preteatment required to induce Fas expression on these cells. Fucosidase activity decreased after induction of apoptosis suggesting that it was not responsible for the loss of fucosylated structures. In the rat PRO cell line, H blood group antigens are mainly carried by a high molecular weight variant of CD44. It could be shown that the loss of H antigen after induction of apoptosis correlated with a loss of the carrier glycoprotein.

Biochemical analysis of ocular surface mucin abnormalities in dry eye: the canine model

This study examines the canine model of keratoconjunctivitis sicca (KCS, 'dry eye') in order to establish the biochemical basis of altered ocular mucin secretion in this condition. It follows a previous examination of ocular mucins in the normal dog. Mucus was collected by suction from the ocular surface of dogs with KCS, and dispersed in guanidine hydrochloride containing a cocktail of protease inhibitors. Caesium chloride density gradient centrifugation was used to separate floating 'rafts' of cell membranes from gradients containing secreted mucins. Gradient fractions were collected into pools on the basis of differential staining by Periodic Acid Schiff, Wheat Germ Agglutinin, and antibodies to MUC5AC peptide. High molecular weight glycoproteins were purified from the pooled material by gel filtration chromatography. Membrane-associated glycoproteins were also derived from the membrane rafts using octyl glucoside extraction and/or reduction and alkylation. Secreted mucins and membrane extracts from KCS samples were compared to equivalent material obtained from normal eyes. Density gradient staining profiles for normal and KCS mucus were similar over the buoyant density range typical for secreted mucins, enabling the collection of identical pools of gradient fractions for direct comparison. The following differences were observed in KCS secreted mucins compared to normal samples: an increase in the proportion of mucin with low buoyant density; a decrease in mannose content detected with Concanavalin A lectin; an increase in N-acetylglucosamine structures detected with Lycopersicon esculentum lectin; increased migration and lack of evidence for distinct subunit structure on agarose gels. In membrane extracts, the main difference was the presence of T antigen (Gal beta 1-3GalNAc) in KCS. These results demonstrate alterations in the subunit linkage of mucins in KCS, and suggest that glycosylation, core protein expression and/or post-synthetic modification of ocular surface mucins may also be changed.

Mucus glycoproteins from pig gastric mucosa: different mucins are produced by the surface epithelium and the glands

An antibody (PGM2B) recognizing a pig gastric-mucin apoprotein reacts with the surface epithelium of pig gastric mucosa. Virtually no reactivity was observed over the mucin-producing cells in the glands, which were recognized by the GlcNAc-selective Griffonia simplicifolia II (GSA-II) lectin. Mucins from the glandular tissue of the cardiac region, corpus and antrum were purified using isopycnic density-gradient centrifugation in CsCl/guanidinium chloride. In the cardiac region, two major mucin populations at 1.5 and 1.4 g/ml were identified. The high-density population reacted preferentially with the PGM2B antibody and resembled mucins from the surface epithelium of this region, whereas the low-density population reacted strongly with the GSA-II lectin and appeared to originate from the glands. In the glandular tissue of corpus, a component with strong GSA-II lectin reactivity, which was distinctly different from the surface mucins from this region, was found at 1.4 g/ml, thus resembling the gland component from the cardiac region. Mucins from antrum glandular tissue contained at least two GSA-II lectin-reactive populations banding at 1.5 and 1.4 g/ml, respectively. Gland mucins from all regions were large oligomeric glycoproteins and heterogeneous with respect to charge properties, as shown by using rate-zonal centrifugation and ion-exchange HPLC, respectively. Gel chromatography of mucin glycopeptides showed that gland mucins from antrum and corpus contained significantly longer glycosylated domains than those from the surface mucosa. Thus, mucins from pig gastric glandular tissue comprise a number of large and oligomeric glycoproteins that differ from those from the surface epithelium in buoyant density, apoprotein structure and carbohydrate substitution.

Gastric M1 mucin, an early oncofetal marker of colon carcinogenesis, is encoded by the MUC5AC gene

Gastric M1 mucin and the MUC5AC gene show a similar oncofetal expression in the colon. Our aim was to determine whether M1 mucin is the product of the MUC5AC gene. A recombinant baculovirus encoding the C-terminal portion of the MUC5AC gene as a fusion protein was isolated and the immunoreactivity of the recombinant mucin (rM) toward M1 antibodies studied. Chicken antibodies also were raised against purified rM. Besides its reactivity with L56/C, a serum recognizing the bacterially expressed MUC5AC gene product, rM was endowed with M1 immunoreactivity: (i) rM-expressing cells were stained specifically with anti-M1 serum and with the monoclonal antibody (MAb) 21M1, defining the M1-f epitope; (ii) both L56/C and anti-M1 antibodies recognized the same bands in immunoblots of rM-containing cell extracts; (iii) the 21M1 antibody reacted with rM in an immunoradiometric assay. Among the 7 M1 epitopes, M1-f was the only one encoded by the 3' portion of the MUC5AC gene. It was the only epitope detected in a native mucin M1-derived 170 kDa bromelain proteolytic fragment. Furthermore, the staining patterns of human tissues obtained with either anti-rM chicken antibodies or anti-M1 antibodies were identical. We conclude that M1 immunoreactivity is encoded at least in part by the MUC5AC gene.

Heterogeneity in the protein cores of mucins isolated from human middle ear effusions: evidence for expression of different mucin gene products

High molecular weight mucins were isolated and purified from human middle ear effusions of children with Otitis Media with Effusion (OME) classified into three groups, (1) thick and (2) thin from anatomically normal children and (3) effusions from cleft palate patients. Amino acid analyses of the purified mucins from the three pools were similar but not identical with characteristic contents of serine threonine and proline (32%, 28%, and 38% for pools (1) (2) and (3) respectively). Proteinase resistant glycopeptide fragments corresponding to the tandem repeat domains of cloned mucin genes showed marked differences both between the three mucin pools and with the composition of the tandem repeat sequences of the cloned mucin genes expressed in the airways. Studies on the antigenic identity of middle ear mucins found an epitope likely to be present on MUC5AC, but only accounting for a maximum of 15% by weight and no reactivity was found with antibodies to MUC2 or MUC1. A polyclonal antibody raised to thick effusion mucins reacted strongly with human salivary mucin suggesting the presence of MUC5B epitopes. These studies suggest that more than one mucin gene product is secreted by the human middle ear mucosa and that there may be further mucin genes expressed by the middle ear that have yet to be cloned.

CA 19-9 ELISA test: a new method for studying mucus changes in tears

AIMS

This study investigated mucus changes in the tears in various eye conditions using impression cytology. The quantity of mucins was measured by enzyme linked immunosorbent assay (ELISA) using the tumour marker CA 19-9. This assay quantifies the sialylated Lewis(a) structure mainly associated with ocular mucins.

METHODS

Impression cytology was performed using a cellulose nitrate membrane, on 53 healthy patients, 50 glaucoma patients treated with beta blockers, 24 patients suffering from dry eye syndrome, and 45 contact lens wearers. The tear film glycoproteins were eluted and CA 19-9 was measured.

RESULTS

CA 19-9 content expressed as kilo units (kU) per microgram of tears was significantly decreased in dry eye syndrome (25.8 kU (SD 17.3)/microgram) (p < 0.05), glaucoma patients over 60 years (28.9 (19.5) kU/microgram) (p < 0.05), and contact lens wearers (28.4 kU (18)/microgram) (p < 0.05), when compared with healthy individuals (39.4 kU (22.2)/microgram).

CONCLUSION

Impression cytology can be regarded as a valuable method for obtaining samples of glycoconjugates of mucin. The decrease of sialylated chains observed with this method confirms the hypothesis that some quantitative changes in the tear film may be encountered in ocular surface disorders.

Expression of A and H blood-group and of CD44 antigens during chemical rat colonic carcinogenesis

Using an experimental model of rat colon adenocarcinoma, we have recently shown that the presence of H blood-group antigen on variants of the CD44 adhesion molecule carrying amino acids encoded by exon v6 (CD44v6), increased the cells' tumorigenicity. In the present study, colon adenocarcinomas were induced by 1,2-dimethylhydrazine treatment in rats. Using immunohistochemistry, biopsies of normal, precancerous and carcinomatous colon mucosa were evaluated for expression A and H blood group antigens and CD44s and CD44v6 antigens. Normal rat colon showed strong and homogeneous expression of blood-group antigen A, but weak expression of H antigen. Several weeks before the appearance of tumours, dysplastic glands were strongly stained with anti-H reagents, while their A antigen was lost. Expression of CD44v6 was weak and restricted to some cells at the bottom of normal crypts. No obvious change was observed before appearance of severe dysplasia. In carcinomas, a strong but irregular expression of A, H and CD44v6 antigens was observed. In moderately differentiated carcinomas, A and H antigens were present at the apical surface of cells, whereas CD44v6 was found at the basolateral side. Only carcinomatous cells with loss of polarity, found in poorly differentiated cancers or infiltrated in the muscularis mucosae, were found to coexpress blood-group H or A and CD44v6 antigens at their surface.

The lipopolysaccharide of Helicobacter mustelae type strain ATCC 43772 expresses the monofucosyl A type 1 histo-blood group epitope

The lipopolysaccharide of Helicobacter mustelae type strain ATCC 43772 was obtained by phenol-water extraction of bacterial cells. Structural investigations were made on the lipid A free saccharide moiety released from the lipopolysaccharide by mild acetic acid hydrolysis. Nuclear magnetic resonance, gas liquid chromatography-mass spectrometry and fast atom bombardment-mass spectrometry were employed in the characterization of products from chemical manipulations. A monoclonal antibody specific for blood group A reacted strongly with lipopolysaccharide of H. mustelae. Chemical and serological data showed that the outer core region of the lipopolysaccharide from H. mustelae ATCC 43772 expresses the monofucosyl A type 1, alpha-D-GalNAc-(1-->3)-[alpha-L-Fuc-(1-->2]-beta-D-Gal-(1-->3)- beta-D-GlcNAc, blood group determinant, a mimic of animal cell surface glycolipids and glycoproteins.

Detection of gastric mucins (M1 antigens) in cyst fluid for the diagnosis of cystic lesions of the pancreas

Mucinous cystic tumors of the pancreas must be distinguished from other cystic lesions because of their potential malignancy. Our purpose was to assess the reliability of gastric M1 mucin analysis in the fluid of cystic lesions of the pancreas in comparison or association with carcinoembryonic antigen. M1 mucin and carcinoembryonic antigen were measured in cyst fluid obtained preoperatively by fine-needle aspiration. The lesions consisted of 12 serous cystadenomas, 9 mucinous cystadenomas, 8 cystadenocarcinomas and 6 intraductal mucinous hypersecreting neoplasms. Thirty pancreatic pseudocysts complicating well-documented chronic pancreatitis were also examined. In addition, M1 mucins were localized by immunoperoxidase staining in fetal and normal adult pancreas and in mucinous and serous tumors. Carcinoembryonic values of > 20 ng/ml and M1 mucin values of > 50 U M1/ml represented 82 and 78% sensitivity, respectively, as well as 100% specificity for distinguishing mucinous lesions from serous cystadenomas; the sensitivity for this purpose was 100% using these criteria in combination. Carcinoembryonic antigen values of > 300 ng/ml and M1 mucin values of > 1,200 U M1/ml represented 56 and 30% sensitivity, respectively, as well as 100% specificity for distinguishing mucinous lesions from pseudocysts; the sensitivity for this purpose was 60% using these criteria in combination. By immunohistology, M1 mucins were detected in the wall of mucinous lesions but not in fetal and normal adult pancreas and in serous cystadenomas. Measurement of M1 mucin antigen in cyst fluid could thus improve the diagnosis of mucinous cystic lesions of the pancreas.

Defective ATP-dependent mucin secretion by cystic fibrosis pancreatic epithelial cells

The response of confluent monolayers of normal and cystic fibrosis (CF) pancreatic epithelial cells to stimulation by extracellular ATP and ATP analogues was investigated in terms of mucin secretion. Mucin secretion was measured as release of M1 antigens by a direct sandwich enzyme immunoassay. Extracellular ATP provoked rapid (< or = 15 min) and strong mucin secretion (+ 480 +/- 35%) by the normal pancreatic cell lines but was not able to induce mucin secretion by the CF cell lines. The order of efficacy of nucleotide agonists with ATP > ADP > AMP > adenosine was that of typical P2-purinergic receptors. ATP induced a rapid and transient intracellular [Ca2+] mobilization in both normal and CF pancreatic epithelial cells. This work demonstrated that CFTR seemed to mediate ATP-dependent mucin secretion.

Typing of Helicobacter pylori with monoclonal antibodies against Lewis antigens in lipopolysaccharide

Recently, it has been shown that the lipopolysaccharide (LPS) O antigen of Helicobacter pylori contains Lewis x (Lex), Lewis y (Ley), or both Lex and Ley antigens. We applied a serotyping method for H. pylori by an enzyme-linked immunosorbent assay with monoclonal antibodies (MAbs) specific for these antigens and the related fucosylated H type 1 (H1) antigen. The selected MAbs recognized the Lex and/or Ley structures in the LPS of H. pylori. The agreement between the results of biochemical compositional analysis and the serological data validated our serotyping system. A total of 152 strains from different geographic origins (The Netherlands, Canada, Poland, Italy, and People's Republic of China) were examined for typeability based on the presence of Lewis antigens. One hundred twenty-nine (84.9%) strains were typeable, and 12 different serotyping patterns were observed; 80.9% of the strains contained Lex and/or Le(y) antigens, and 18.4% reacted with the MAb against the related H1 antigen either alone or in combination with the Lex and/or Ley antigen. Our results show that the Lex and Ley antigens are frequently encountered in the LPS of H. pylori strains from various geographic origins. This typing method is an easy-to-perform technique, which can be used for strain differentiation in epidemiological studies of H. pylori infections.

Direct double antibody sandwich immunoassay of mucin M1 epitopes in human mucus secreting pancreatic cell lines

A direct sandwich enzyme immunoassay using two monoclonal antibodies was developed in order to quantify mucin M1 antigens produced by two pancreatic adenocarcinoma cell lines: CAPAN-1 and CFPAC-1. As a solid phase, the wells of a microtiter plate were coated with a first monoclonal antibody, 1-13 M1 and the biotinylated monoclonal conjugate 9-13 M1 was used as the second antibody. The assay was optimized with streptavidin-peroxidase. The detection limit of the assay is 1.6 ng/ml. This ELISA is highly specific, sensitive, reproducible and quickly performed. It will permit the comparison of mucin exocytosis by the two cell lines in response to secretagogue agents and may help in the study of the pathogenesis of mucus hypersecretion such as cystic fibrosis.

Changes in expression and subcellular localization of annexin IV in rabbit kidney proximal tubule cells during primary culture

In the present study, we investigated the polarized expression of annexin IV at various stages in the growth of rabbit kidney proximal tubule cells (PTC) in primary cultures. The results of immunoblotting analysis and indirect immunofluorescence studies using a specific anti-annexin IV monoclonal antibody, indicated that annexin IV is expressed in proximal tubule cultured cells, although it was not detected in the proximal tubules present in frozen sections of kidney cortex and freshly isolated proximal tubule cells. In either non-confluent or confluent cells which remained attached to the collagen-coated support, annexin IV was mainly concentrated around the nucleus, whereas in PTC forming the monolayer of domes, it was restricted to the basolateral membrane domain. This basolateral localization was identical to that observed in other polarized epithelial cell types such as enterocytes. When the domes burst, the cells returned to the collagen-coated support and the annexin IV was again localized around the nuclei. The fact that the change of localization was very rapid suggested the existence of a considerable difference between the differentiation states of dome forming and adherent confluent cells. Moreover, a transient association of annexin IV with the basal body of apically located cilia also seemed to be correlated with a particular polarization state and/or differentiation states of adherent cultured cells, corresponding to the beginning of the polarized expression of aminopeptidase N, a hydrolase located in the apical brush border membrane, and to the falling of cells onto the support, subsequent to the bursting of the domes. In conclusion, these results provide evidence that annexin IV may constitute a new marker of the basolateral membrane domain of polarized epithelial renal cells in primary cultures.

Expression and glycosylation of the filamentous brush border glycocalyx (FBBG) during rabbit enterocyte differentiation along the crypt-villus axis

The filamentous brush border glycocalyx forming the ‘enteric surface coat’ of the intestinal epithelium is composed in rabbits of a 400 kDa mucin-type glycoprotein, which was purified using the 3A4 monoclonal antibody. This monoclonal antibody recognizes a filamentous brush border glycocalyx-specific glycosidic structure containing an O-acetylated sialic acid, which is absent from all the other glycoproteins in the epithelium, with the exception of certain goblet cell mucins. Here we establish that only 50% of the rabbits tested synthesized this glycosidic structure. Upon immunolabeling surface epithelia and sections of jejunum from these rabbits, the carbohydrate epitope recognized by the 3A4 mAb was found to be present on the filamentous brush border glycocalyx of a variable number of enterocytes, which were patchily distributed over all the villi. This heterogeneous expression of 3A4 antigenicity, which was also observed in the crypts, suggests the existence of differences between the patterns of differentiation of enterocytes, which results in the expression of different pools of glycosyltransferases and/or acetyl transferases. In mature enterocytes, the 3A4 determinants were present only on the filamentous brush border glycocalyx, which is anchored solely to the membrane microdomain at the tip of brush border microvilli. However, expression of 3A4 antigenicity begins in the median third of crypts, in enterocytes with a short, thin brush border devoid of apical filamentous brush border glycocalyx. Here the 3A4 epitopes were present over the whole brush border membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Repression of the Lewis fucosyl transferase by retinoic acid increases apical sialosyl Lewis(a) secretion in colorectal carcinoma cultures

The rate of polarised secretion of sialosyl Lewis(a)(19-9) molecular species (SiaLeams) by SW1116 colorectal carcinoma cells is stimulated at least ninefold by the presence of 3 microM retinoic acid (RA). In order to investigate the intracellular origins of this augmentation, carcinoma cell membranes, membrane subfractions, and media were studied to determine alterations in sialosyl Lewis(a) levels, oligosaccharide composition, and core structures accompanying the capacity to increase export of this epitope. We observed a nine- to twentyfold increase in sialosyl Lewis(a) epitope levels in a light membrane subfraction from RA-treated cells. Antigenic molecules of < 200,000 M(r) on acrylamide gradient gels were concentrated in two doublets in the apparent M(r) range 106,000-152,000 on Western blots. Carbohydrate analyses of oligosaccharides from SiaLeams of membrane subfractions and apical media indicated much higher fucose/mannose, fucose/sialic, fucose/sialosyl Lewis(a), fucose/total CHO, and (3H) fucose incorporation in control samples than RA samples. Western blots of samples from membrane subfractions and media indicated that, in contrast to the effect of RA on the sialosyl Lewis(a) epitope, RA treatment did not augment cysteine-rich, PDTRP, blood group H-2, blood group A, and EGF receptor-like region epitopes in the media. In addition, Northern blots using the Lewis fucosyl transferase (FTIII) cDNA showed a dramatic diminution of mRNA encoding FTIII but apparently unaltered levels of sialyl transferase (ST4) mRNA. Since subterminal fucosylation of lactosyl termini blocks terminal sialylation, we conclude that one mechanism of sialosyl Lewis(a) induction in this culture system is the lower expression of the Lewis fucosyl transferase mRNA. Therefore less subterminal fucosylation of GlcNAc permits the prior sialylation of terminal Gal beta 1-3 moieties at oligosaccharide termini destined for export from the Golgi.

The filamentous brush border glycocalyx, a mucin-like marker of enterocyte hyper-polarization

The probably sole constituent of the filamentous brush border glycocalyx, which has been defined on the basis of electron microscopic data as a set of filaments radiating from the tip of rabbit intestinal brush border microvilli, has been purified. It consists of a mucin-type glycoprotein that can be solubilized by either Triton extraction or papain treatment of the brush border membrane vesicles but is insensitive to phosphatidylinositol phospholipase C. The detergent- and papain-solubilized forms both have the same apparent molecular mass of 400 kDa (SDS/PAGE). This suggests that the filamentous brush border glycocalyx may be anchored to the membrane by a small hydrophobic peptidic tail. Ser, Thr, Pro and Ala amount to 65% of the protein core amino acid residues. The glycosidic moiety, which amounts to 73% of the molecular mass, has high O-acetylated sialic acid contents. A monoclonal antibody (3A4) raised against the purified material was produced which specifically recognized the 400-kDa band by immunoprecipitation and immunoblotting, and the filamentous brush border glycocalyx of villus enterocytes when jejunum sections were immunolabelled. The 3A4 determinant was identified with a filamentous brush border glycocalyx-specific carbohydrate structure containing an O-acetylated sialic acid. The fact that the labeled glycocalyx was anchored entirely in a membrane microdomain at the tip of the microvilli shows that mature enterocytes are hyper-polarized epithelial cells.

The expression of carbohydrate blood group antigens correlates with heat resistance

Recent data indicate that cells may resist heat shock via more than one route: heat shock protein synthesis and other still ill-defined mechanisms. We investigated this phenomenon using four types of cells derived from a single rat colon carcinoma: clones REGb and PROb; PRO A+, a glycosylation variant of PROb selected for its high expression of blood group A antigen; and Ph8, a thermoresistant variant of PROb selected by repeated sublethal heat treatments. Basal heat resistance was clearly associated with the level of cell surface expression of blood group H and A antigens. Biosynthesis of these carbohydrate structures requires two glycosyltransferases, H and A enzymes, whose activities are also correlated with basal heat resistance. In addition, heat sensitive REGb cells were rendered more resistant by transfection with the gene encoding for H enzyme, allowing expression of H antigen. Thus, these terminal glycosylations could play a role as cellular protectors against heat treatment. Blood group carbohydrate antigens were mainly located on O-linked carbohydrate chains of a major glycoprotein of 200 kDa and to a lesser extent on N-linked chains. Only trace amounts were present as glycolipids.

Effects of VIP on the regulation of mucin secretion in cultured human pancreatic cancer cells (Capan-1)

The effects of Vasoactive intestinal peptide (VIP) on mucin secretion in the pancreatic cancer Capan-1 cell line were studied by Enzyme-linked-immunosorbent-assay (ELISA), and by light and electron microscopy using immunocytological methods. During the exponential growth phase, mucins were accumulated in the cytoplasm of cells and slowly exocytosed. In contrast, there was enhanced exocytosis of mucins during the stationary phase when the cells were well-polarized. Moreover, during this phase, VIP induced a dose-dependent rise in mucin content in the extracellular medium. The reaction with anti-M1 monoclonal antibodies, which recognize specifically the peptide core of gastric mucins, showed an accumulation of secretion granules near the apex of well-polarized cells together with fusion of the granule and plasma membranes after VIP stimulation. Moreover, mucin exocytosis was stimulated by Pituitary adenylate cyclase activating polypeptide (PACAP) and secretin. It was also increased after forskolin treatment suggesting that this mechanism was cAMP-dependent. Our results suggested that exocytosis of mucins could be under the control of VIP in pancreatic duct cells of the Capan-1 cell line.

Characterization of OM-B monoclonal antibody-defined antigen associated with mucinous type human ovarian tumor

Partial characterization of the OM-B antigen associated with mucinous-type ovarian tumors was conducted. This antigen was defined by OM-B monoclonal antibody, which was raised against a mucinous-type ovarian tumor, and was present in all the mucinous-type tumors tested, but only a fraction of serous-type tumors. The OM-B crude antigen preparation fractionated from cystic fluids had a density of 1.40-1.43 g/ml, with a high neutral sugar content. Molecular mass (M(r)) estimated by gel filtration was more than 2,000,000. Trypsinization of the antigen preparation under appropriate conditions resulted in two major bands and one minor band with molecular sizes of less than M(r) 250,000, as detected by immunoblotting. Immunoaffinity chromatography was then conducted and the amino acid composition of the purified product was determined; the high contents of serine, threonine and proline are characteristic of a mucin. Binding inhibition enzyme-linked immunosorbent assay was developed to measure OM-B antigen activity in cystic fluids and sera from patients with mucinous-type tumors. The antigen was easily detected in most cystic fluids, but not in sera, suggesting that improvement in the sensitivity of this assay is necessary before its utilization for serum diagnosis will be feasible.

Immunohistological characterization of mucin epitopes by pre-treatment of gastro-intestinal sections with periodic acid

Periodate pretreatment of paraffin sections of ethanol-fixed gastrointestinal mucosae was used to characterize the carbohydrate or peptidic nature of mucin epitopes by immunoperoxidase. Immunoreactivity of monoclonal antibodies (MAbs) against histo-blood group related carbohydrate epitopes such as A, Lea, Lec, Sialosyl Lea, H type 2, I, T, Tn and sialosyl Tn dramatically decreased or even disappeared after periodate pretreatment of deparaffinized sections. In contrast, the immunoreactivity of MAbs against peptide mucin epitopes such as the gastric M1 mucin epitopes was almost unaffected by this treatment. Moreover, periodate treatment revealed cryptic peptide M1 mucin epitopes and the peptide MUSE11 epitope associated with the 20 amino acid tandem repeat (PDTRPAPGSTAPPAHGVTSA). An increase of cross-reactions of anti-human M1 MAbs with gastric epithelium of different vertebrate species was detected with periodate treatment. Our results suggest that this method can be useful for preliminary characterization of the biochemical nature of mucin epitopes (peptidic or saccharidic) and for demasking peptidic tumour markers which are hidden by saccharide molecules in normal tissues.

Serological and chemical specificities of twelve monoclonal anti-Lea and anti-Leb antibodies

The serological specificities of twelve hybridomas were compared as to their chemical reactivity as determined using direct binding to synthetic carbohydrate structures. All anti-Lea cross-react with type-1-precursor structures and three different variants of anti-Lea could be defined by their binding to type-3-precursor chains, sialylated compounds and the monosaccharide D-galactose. Three major reactivity patterns were also identified among anti-Leb reagents. Anti-LebL cross-react with Lea and do not significantly bind to H-related structures. Anti-LebH,L had both anti-LebL-like activity (cross-reaction with Lea) and anti-LebH-like activity (cross-reaction with H). Finally, anti-LebH cross-reacts strongly with H compounds and do not bind to Lea. The binding pattern of anti-LebL suggests that these antibodies have lower affinity for ALeb and BLeb pentasaccharides than anti-LebH. All these specificities are not absolute, but rather are expressed as members of a quantitative progressive varying series, suggesting the existence of a whole range of antibody specificities gradually changing from Lea----Lea,b----LebL----LebH,L----LebH. The results suggest that anti-LebL will always cross-react with Lea and that anti-LebH will always cross-react with H related structures. However, under certain well-defined conditions these cross-reactions may not be apparent and antibodies might behave as specific anti-Lea or anti-Leb in certain tests.

Evidence for shared epitopes within the 'naked' protein domains of human mucus glycoproteins. A study performed by using polyclonal antibodies and electron microscopy

Polyclonal antibodies were raised in rabbits towards reduced subunits of human cervical mucus glycoproteins. The reduced subunits almost completely inhibited the antiserum, whereas the intact mucins and the heavily glycosylated fragments obtained after digestion of reduced subunits with trypsin (T-domains) caused only partial inhibition. Periodate oxidation of intact mucins, reduced subunits and T-domains caused no effect on the antibody response, and fragments obtained by more extensive proteolysis of the reduced subunits (P-domains) showed no inhibitory activity. By using electron microscopy, antibodies from T-domain-adsorbed antisera were revealed as bound to cervical mucin reduced subunits, either directly or with colloidal gold-Protein A. Binding sites (100-150 nm apart) were observed at the ends and at internal positions of the reduced subunits. We conclude that the antibodies do not recognize carbohydrate structures but are directed to two kinds of protein epitopes, one shared by whole mucins, reduced subunits and T-domains, and the other specific to the reduced subunit fragment. The latter epitopes are 'cryptic' and are probably shielded within folded protein domains stabilized by disulphide bonds. Human bronchial, cervical, gastric and salivary mucus glycoproteins share some of these cryptic epitopes.

Oncofetal mucin M1 epitope family: characterization and expression during colonic carcinogenesis

The gastric mucin M1 antigens, markers associated with colonic carcinogenesis, have been characterized by new antimucin monoclonal antibodies (MAbs). These MAbs, obtained against mucins isolated from a human ovarian mucinous cyst (MAbs 19M1, 21M1 and 45M1) and from a pancreatic adenocarcinoma (MAb 96RA), were compared with 5 other anti-M1 mucin MAbs described previously, which characterized the a, b, c, d and e mucin M1 epitopes. Using immunoperoxidase, these new MAbs exclusively stained the surface gastric epithelium of normal human gastro-intestinal tract and reacted with fetal, precancerous and cancerous colonic mucosa, but not with normal colon. Immunoradiofixation studies showed that these new MAbs are directed against 3 epitopes (f, g and h) which are different from the a, b, c, d and e mucin M1 epitopes, though present on the same a immunoreactive high-molecular-weight components (greater than 1,000 kDa) with a density of 1.4 by CsCl-density-gradient ultracentrifugation. M1 antigenicity is characterized by a family of 8 different M1 epitopes which were destroyed with beta-mercaptoethanol (except for the f epitope), sensitive to a 5 hr trypsin treatment and resistant to 5 mM periodate (except for the h epitope). Some epitopes (b, c and d) showed increasing immunoreactivity after 20 mM periodate treatment, suggesting cryptic location. In rat-colon adenocarcinomas, M1 mucin epitopes were masked but could be decrypted using high periodate treatment, similar to normal rat gastric mucosa, thus suggesting the absence of drastic changes in the saccharide coat of the peptide mucin portion bearing M1 epitopes. Cryptic location, periodate resistance, sensitivity to protease and conformational behavior strongly suggest that the peptidic core of gastric (or fetal colonic) mucin plays a role in M1 immunoreactivity. Indeed, the resurgence of M1 antigens during colonic carcinogenesis is due to re-expression of the peptide core of gastric (or fetal colonic) mucins.

The foveolar cell component of gastric cancer

M1, a mucin antigen, and cathepsin E, an aspartic proteinase, are both expressed in normal gastric superficial-foveolar epithelial cells. In this study, we determined by immunohistochemical staining the prevalence of these antigens in 316 gastric cancers representative of the main histologic types and stages of the disease. M1 was expressed in 201 cases (64%) and cathepsin E was expressed in 235 cases (75%) of the 313 cases investigated. Both antigens were expressed more commonly in diffuse and mixed cancers than in glandular tumors. M1 was found in 64 of 83 (77%) diffuse cancers and in 48 of 59 (81%) mixed cancers, but in only 74 of 146 (51%) glandular cancers. For cathepsin E, the prevalence was 93% in diffuse cancer, 81% in mixed cancer, and 71% in the 143 glandular cancers examined. Among 25 mucoid tumors, 15 (60%) expressed M1 but only eight (32%) expressed cathepsin E. Overall, 262 (84%) of the tumors expressed at least one of these antigens and of these, 173 (66%) expressed both antigens. No significant difference in the prevalence of M1 or cathepsin E was found between early and advanced cancer or between metastatic and nonmetastatic cancer. The two markers differed in their intracellular localization. In superficial-foveolar cells, M1 immunostaining was concentrated in secretory granules, Golgi complex, and luminal mucous, whereas cathepsin E was found in the endoplasmic reticulum. Moreover, cathepsin E, but not M1, was found in the enterocytes of duodenal villi and, occasionally, in mucopeptic cells. Parallel histochemical and ultrastructural investigations confirmed the occurrence in gastric cancer of foveolar-type cells, manifested by periodic acid-Schiff- and/or alcian blue-reactive mucous granules having a punctate substructure. We conclude that superficial-foveolar cell differentiation is common in gastric cancer and is a major component of this type of tumor. However, pure foveolar cell differentiation is rare. Rather, most gastric cancers consist of cells exhibiting features of foveolar, intestinal, and mucopeptic cell lines.

Differential susceptibility to experimental allergic encephalomyelitis (EAE) in genetically defined A+ and A- rabbits

Only one out of 57 A-/A- rabbits immunized with rat or guinea-pig myelin developed clinical signs suggestive of EAE. On the contrary, clinical signs of acute or chronic EAE were found in two thirds of the 102 A+/A+ and A+/A- rabbits immunized in the same way. About one third of the diseased animals had reversible acute EAE, another third died paralysed and the last third developed chronic progressive or relapsing EAE. Incidence and severity of EAE symptoms were positively correlated with age and no significant difference was observed between males and females. Cellular and humoral anti-myelin responses were stronger in A+ than in A- rabbits. Anti-A antibodies, on the contrary, were only detected in A- rabbits. The A+ rabbits did not make Anti-A at any time. Anti-A antibodies increased early, in A- rabbits, after immunization with myelin (11-30 days) and were later replaced by a low, but specific, anti-myelin response (60-90 days). The gene responsible for the susceptibility to EAE is autosomal and dominant over resistance. This gene must be closely linked to the A locus or might be the A gene itself. The low susceptibility of A- rabbits to the disease could be, in this last case, a consequence of the competition between the early anti-A and the normal anti-myelin immune responses, both induced by the injection of myelin.

Evidence of mucin M1 antigens in seminal plasma and normal cells of human prostatic urethra in relation to embryonic development and tumors

By employing immunoperoxidase methodology, using monoclonal antibodies against the peptide core of gastric mucins (M1 antigens), we demonstrate the presence of M1 mucin-producing cells that are associated with the prostatic urethral epithelium and located mainly in the veru montanum area near the prostatic ductal and utriculus junctions. The significance of these M1 cells is not yet clear. Using an immunoradiometric assay, these M1 mucins were found predominantly in the prostatic fraction obtained from seminal plasma. By chromatography on Sepharose 6B and 2B and cesium chloride gradient centrifugation, we demonstrate that high-molecular-weight components (greater than 10(7) Da) show a density of 1.45 g/ml, similar to mucins, and are immunochemically related to peptidic gastric M1 mucins. The particular location of these M1 antigens in prostatic adult urethra and their fetal expression in cloacal structures suggest that, in males, the prostatic urethral epithelium includes some remnant cells from the enteric cloaca. Finally, the presence of mucin-containing cells in the prostatic urethra could possibly explain the histogenesis of the rare benign villous tumors and primary mucinous adenocarcinomas arising from the prostatic urethral epithelium.

Expression of ABH, Lewis and related tissue antigens in the human thymus

Expression of ABH, Lewis and related antigens was studied in the thymus of children of known ABO, Lewis and secretor status using a panel of specific reagents. ABH and Lewis antigens partly under control of the secretor status were expressed on the Hassals' bodies and a large fraction of the medullary epithelial cells. The sialyl-Lea antigen was only present on some Hassals' bodies of Lewis-positive individuals. ABH but not Lewis antigens were also present on cortical epithelial cells but this was independent of the secretor status. The X, sialyl-X and Y antigens were only expressed on Hassals' bodies irrespective of the ABO, Lewis or secretor phenotype. Furthermore, the anti-X and sialyl-X antibodies labelled a subset of leucocytes of all the individuals tested. These results show that the genetic control of the expression of ABH and Lewis glycosidic tissue alloantigens in the thymus is different on cortical and medullary epithelial cells and stress the heterogeneity of the thymus epithelial cells.