Application of lectins for detection of goblet cell carbohydrates of the human conjunctiva

Low Dose Carbon Black Nanoparticle Exposure Does Not Aggravate Allergic Airway Inflammation in Mice Irrespective of the Presence of Surface Polycyclic Aromatic Hydrocarbons

Exposure to exogenous noxae, such as particulate matter, can trigger acute aggravations of allergic asthma—a chronic inflammatory airway disease. We tested whether Carbon Black nanoparticles (CBNP) with or without surface polycyclic aromatic hydrocarbons (PAH) aggravate an established allergic airway inflammation in mice. In an ovalbumin mouse model, Printex^®90 (P90), P90 coated with benzo[a]pyrene (P90-BaP) or 9-nitroanthracene (P90-9NA), or acetylene soot exhibiting a mixture of surface PAH (AS-PAH) was administered twice (70 µL, 100 µg/mL) during an established allergic airway inflammation. We analyzed the immune cell numbers and chemokine/cytokine profiles in bronchoalveolar lavages, the mRNA expressions of markers for PAH metabolism (Cyp1a1, 1b1), oxidative stress (HO-1, Gr, Gpx-3), inflammation (KC, Mcp-1, IL-6, IL-13, IL-17a), mucin synthesis (Muc5ac, Muc5b), the histology of mucus-producing goblet cells, ciliary beat frequency (CBF), and the particle transport speed. CBNP had a comparable primary particle size, hydrodynamic diameter, and ζ-potential, but differed in the specific surface area (P90 > P90-BaP = P90-9NA = AS-PAH) and surface chemistry. None of the CBNP tested increased any parameter related to inflammation. The unmodified P90, however, decreased the tracheal CBF, decreased the Muc5b in intrapulmonary airways, but increased the tracheal Muc5ac. Our results demonstrated that irrespective of the surface PAH, a low dose of CBNP does not acutely aggravate an established allergic airway inflammation in mice.

Biological effects of carbon black nanoparticles are changed by surface coating with polycyclic aromatic hydrocarbons

Background

Carbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). The toxicity of CBNP has been attributed to their large surface area, and through adsorbing intrinsically toxic substances, such as polycyclic aromatic hydrocarbons (PAH). It is not clear whether a PAH surface coating changes the toxicological properties of CBNP by influencing their physicochemical properties, through the specific toxicity of the surface-bound PAH, or by a combination of both.

Methods

Printex^®90 (P90) was used as CBNP; the comparators were P90 coated with either benzo[a]pyrene (BaP) or 9-nitroanthracene (9NA), and soot from acetylene combustion that bears various PAHs on the surface (AS-PAH). Oxidative stress and IL-8/KC mRNA expression were determined in A549 and bronchial epithelial cells (16HBE14o-, Calu-3), mouse intrapulmonary airways and tracheal epithelial cells. Overall toxicity was tested in a rat inhalation study according to Organization for Economic Co-operation and Development (OECD) criteria. Effects on cytochrome monooxygenase (Cyp) mRNA expression, cell viability and mucociliary clearance were determined in acute exposure models using explanted murine trachea.

Results

All particles had similar primary particle size, shape, hydrodynamic diameter and ζ-potential. All PAH-containing particles had a comparable specific surface area that was approximately one third that of P90. AS-PAH contained a mixture of PAH with expected higher toxicity than BaP or 9NA. PAH-coating reduced some effects of P90 such as IL-8 mRNA expression and oxidative stress in A549 cells, granulocyte influx in the in vivo OECD experiment, and agglomeration of P90 and mucus release in the murine trachea ex vivo. Furthermore, P90-BaP decreased particle transport speed compared to P90 at 10 μg/ml. In contrast, PAH-coating induced IL-8 mRNA expression in bronchial epithelial cell lines, and Cyp mRNA expression and apoptosis in tracheal epithelial cells. In line with the higher toxicity compared to P90-BaP and P90-9NA, AS-PAH had the strongest biological effects both ex vivo and in vivo.

Conclusions

Our results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound PAH, and varies in different target cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-017-0189-1) contains supplementary material, which is available to authorized users.

Mechanisms of cilia-driven transport in the airways in the absence of mucus

Airway mucus is thought to be required for the clearance of inhaled particles by mucociliary transport, but this view has recently been challenged. To test if mucus is necessary for cilia-driven particle transport, we removed mucus from murine and human ex vivo airway preparations by thorough rinsing with buffer with or without additional dithiothreitol washing. The transport of particles with diameters of 4.5 μm, 200 nm, and 40 nm and of bacteria was analyzed by video microscopy. Complete removal of mucus was verified by wheat germ agglutinin staining and by scanning electron microscopy. In the absence of mucus, we observed efficient transport of particles and bacteria by direct cilia-mediated propulsion or via fluid flow generated by ciliary beating. Virus-sized particles had the tendency to attach to cilia. Because direct contact of particles with ciliated cells occurs in the absence of mucus, we examined if this direct interaction changes epithelial function. Neither bacteria- nor LPS-induced nuclear translocation of NF-κB p65 in ciliated cells occurred, indicating that mere contact between ciliated cells and bacteria during transport does not activate the epithelium. Attachment of virus-sized particles to cilia could induce mucus release and/or increase the ciliary beat frequency. Our results indicate that cilia-driven transport of particles with various sizes is possible in murine and human airways without the presence of mucus. If mucus-free transport fails, the epithelium can react by releasing mucus or increasing the ciliary beat frequency to maintain particle transport.

Functional morphology of mucosal goblet cells based on spatial separation of orifice openings to the surface--application to the rabbit bulbar conjunctiva

The purpose of the study was to assess spatial separation of goblet cell orifices observed at the surface of the rabbit bulbar conjunctiva by scanning electron microscopy (SEM) specimens of the bulbar conjunctiva from 8 healthy pigmented rabbits were obtained using a special preparation technique by which the tissue was carefully stretched out during glutaraldehyde fixation. On high magnification prints of SEM images of the conjunctival surface, the locations of goblet cell openings (orifices) to the apical surface were marked and the centre-to-centre spacing between all such orifices measured. Across the regions of interest (ROI), with averaged dimensions of 322 μm × 230 μm (adjusted for tissue shrinkage), the averaged value for the distances between all orifices was 196 μm (range 141-241 μm), with the calculated density of orifices being 412 mm(-2). A sequential order-based analysis of the spatial separation between orifices indicated a predictable value of 6 μm, a separation that showed a nearly linear inter-dependence over distances of at least 200 μm. The openings of goblet cells to the surface of unstimulated bulbar conjunctiva have a organized spatial distribution that is consistent with there being an organized control of goblet cell secretion.

Inductive differentiation of conjunctival goblet cells by γ-secretase inhibitor and construction of recombinant conjunctival epithelium

γ-secretase inhibitor has been shown to promote intestinal goblet cell differentiation. We now demonstrated that the in vitro addition of γ-secretase inhibitor in the culture of human conjunctival epithelial cells significantly promoted the differentiation of conjunctival goblet cells with typical droplet-like phenotype, positive periodic acid-Schiff and goblet cell-specific Muc5Ac, cytokeratin 7 and Helix pomatia agglutinin lectin staining. Moreover, topical application of γ-secretase inhibitor promoted the differentiation of mouse conjunctival goblet cells in vivo. Furthermore, the expression of Notch target gene HES-1 was down-regulated during the differentiation of conjunctival goblet cells. In addition, we found that the recombinant conjunctival epithelium on amniotic membrane showed less goblet cell density and abnormal location when compared with normal conjunctival epithelium, which were improved by the addition of γ-secretase inhibitor in the final induction.

Biopsy harvesting site and distance from the explant affect conjunctival epithelial phenotype ex vivo

The purpose of the study was to investigate if the number of goblet cells expanded ex vivo from a conjunctival explant is affected by the biopsy harvesting site on the conjunctiva and the distance from the explant. Conjunctival explants from six regions: superior and inferior bulbus, fornix, and tarsus of male Sprague-Dawley rats were grown in RPMI 1640 with 10% fetal bovine serum on coverslips for eight days. Histochemical and immunofluorescent staining of goblet (CK-7/UEA-1/MUC5AC), stratified squamous, non-goblet (CK-4), proliferating (PCNA) and progenitor (ABCG2) cells were analyzed by epifluorescence and laser confocal microscopy. Outgrowth was measured with NIH ImageJ. For statistical analysis the Mann-Whitney test and Spearman's rank-order correlation test were used. Cultures from superior and inferior fornix contained the most goblet cells as indicated by the presence of CK-7+, UEA-1+ and MUC5AC+ cells. Superior and inferior forniceal cultures displayed 60.8% ± 9.2% and 64.7% ± 6.7% CK-7+ cells, respectively, compared to the superior tarsal (26.6% ± 8.4%; P < 0.05), superior bulbar (31.0% ± 4.0%; P < 0.05), inferior bulbar (38.5% ± 9.3%; P < 0.05) and inferior tarsal cultures (27.7% ± 8.3%; P < 0.05). While 28.4% ± 6.3% of CK-7+ goblet cells co-labeled with PCNA, only 7.4% ± 1.6% of UEA-1+ goblet cells did (P < 0.01). CK-7+ goblet cells were located at a lower concentration close to the explant (39.8% ± 3.1%) compared to near the leading edge (58.2% ± 4.5%; P < 0.05). Both markers for goblet cell secretory product (UEA-1 and MUC5AC), however, displayed the opposite pattern with a higher percentage of positive cells close to the explant than near the leading edge (P < 0.05). The percentage of CK-4+ cells was higher near the explant compared to near the leading edge (P < 0.01). The percentage of CK-7+ goblet cells in the cultures did not correlate with the outgrowth size (r(s) = -0.086; P = 0.435). The percentage of UEA-1+ goblet cells correlated negatively with outgrowth size (r(s) = -0.347; P < 0.01), whereas the percentage of CK-4+ cells correlated positively with the outgrowth size (r(s) = 0.473; P < 0.05). We conclude that forniceal explants yield the highest number of goblet cells ex vivo and thereby seem to be optimal for goblet cell transplantation. We also suggest that CK-7+/UEA-1- cells represent highly proliferative immature goblet cells. These cells could be important during conjunctival migration as they are mostly located close to the leading edge and their density does not decrease with increasing outgrowth size.

Goblet cells of the normal human bulbar conjunctiva and their assessment by impression cytology sampling

Goblet cells of the conjunctiva are the main source of mucus for the ocular surface. The objectives of this review are to consider the goblet cells as assessed by various histological, cytological and electron microscopy methods, and to assess the consistency of published reports (over more than 25 years) of goblet cell density (GCD) from impression cytology specimens from nominally healthy human subjects. Reported GCD values have been notably variable, with a range from 24 to 2226 cells/mm² for average values. Data analysis suggests that a high density of goblet cells should be expected for the healthy human conjunctiva, with a tendency toward higher values in samples taken from normally covered locations (inferior and superior bulbar conjunctiva) of the open eye (at 973 +/- 789 cells/ mm²) than in samples taken from exposed (interpalpebral) locations (at 427 +/- 376 cells/mm²). No obvious change in GCD was found with respect to age, perhaps because the variability of the data did not allow detection of any age-related decline in GCD. Analyses of published data from 33 other sources indicated a trend for GCD to be lower than normal across a spectrum of ocular surface diseases.

Sialylated glycans and mucins in the lacrimal gland and eyelid of man and pig. Potential receptors for pathogenic microorganisms

The conjunctiva of the eyelid is coated by secretion products from the lacrimal and eyelid glands, and by mucins produced by conjunctival goblet cells, which together form a glycoprotein-rich layer that lubricates and protects the surface of the eye. However, these ocular carbohydrates may also act as adhesives for viruses and bacteria and thereby facilitate their colonization. This paper provides histochemical demonstration of the in situ localization of such carbohydrate receptors in the form of sialylated glycans and mucins in the lacrimal and eyelid glands and conjunctiva from both humans and pigs. The pig is included in this study because viruses of swine origin may be capable of transmission to humans. We found that the human and pig ocular surfaces contain receptors for bacteria and viruses in the form of mucins (both membrane bound and secreted) and carbohydrates terminating in Sialylα2-6Gal epitopes and to a lesser degree in Sialylα2-3Gal. The glycosylation of the human soft palate could indicate a mucinous route for the spread of microorganisms from the eye via the nasolacrimal duct to the nasopharynx and thus to the upper part of the respiratory tract.

Evaluation of ocular surface glycocalyx using lectin-conjugated fluorescein

Purpose:

A glycocalyx plays important roles in the ocular surface epithelium, but there is no direct simple method to evaluate ocular surface glycocalyx. We tested a wheat germ agglutinin conjugate of fluorescein (F-WGA) as a marker to demonstrate ocular surface glycocalyx in vivo.

Methods:

After a 5% F-WGA solution was applied to the eyes of eight healthy volunteers, fluorescent intensities of the central cornea and bulbar conjunctiva were measured by fluorophotometry. A 10% fluorescein-conjugated dextran solution served as the control. Changes in fluorescent intensities of the ocular surface following a challenge with 5% N-acetyl cysteine, a conventional mucolytic agent, were tested in the second experiment. Saline instillation served as a control.

Results:

The ocular surface was diffusely stained by F-WGA. Breakup of the precorneal tear film was not apparent, possibly because F-WGA was bound to the glycocalyx of the ocular surface epithelium. F-WGA fluorescent intensities were high in the superior, nasal, and inferior regions of the bulbar conjunctiva and low in the temporal conjunctiva and cornea. No such regional differences were observed with fluorescein-conjugated dextran. F-WGA fluorescent intensities decreased significantly with N-acetyl cysteine instillation, whereas they were not affected by saline instillation.

Conclusion:

The fluorophotometric method may be used to evaluate the glycocalyx quantitatively in the ocular surface in vivo.

Ocular mucins: Purification, metabolism and functions

Mucins are present at the ocular surface in both secreted and membrane-bound forms. Mucins are produced in partby the conjunctial goblet cells, and are complemented by non-globet secretions. This review focuses on secreted ocular mucins. They are present in the tear film, probably both in gel and soluble form, and play a role in lubrication and ocular defense. It is apparent that mucins are highly adapted to their functions. State of the art techniques for mucin purification and analysis are presented. Density gradient centrifugation, gel filtration, ion-exchange chromatography and agarose gel electrophoresis are discussed, together with methods of oliogosaccharide analysis. Reagents for the detection of mucin are considered in conjunction with these methods, which we have employed in the analysis of human and canine ocular mucins. The general structure of mucins is reviewed. The biosyntheas and glycosylation of ocular mucins are not yet fully understood, and are discussed in relation to currently established concepts. The impaact of disease on the nature and secretion of mucins is considered, as well as the physiological and pathological significance of mucus degradation.

Collagen gel-embedding culture of conjunctival epithelial cells

BACKGROUND

Collagen has effects on cell morphology, differentiation characteristics and function. Using collagen gel culture, several studies about cell differentiation were reported. In this study, the differentiation of rabbit conjunctival epithelial cells in a collagen gel-embedding culture system was investigated by electron microscope and lectin labeling.

METHODS

Rabbit bulbar conjunctival epithelial cells were cultured in type I collagen gel. After 1 and 2 weeks of culture, some of these cells were stained with PAS and seven kinds of lectins, and others were examined by transmission electron microscopy.

RESULTS

The conjunctival epithelial cells cultured within collagen gel formed stratified cell layers and globules with cavities. The inner layer cells facing the cavities showed PAS and lectin staining patterns similar to those of conjunctival goblet cells in vivo, whereas the staining patterns of the outer layer cells on the collagen matrices resembled the patterns of non-goblet epithelial cells. Microvilli on the surface of the innermost cells, basement membranes beneath the outermost cells, tight junctions, adherent junctions, interdigitating folds and desmosomes between cells were identified on electron microscopic examination.

CONCLUSION

These results indicate that cell junction structures of the conjunctival epithelial cells are well developed in collagen gel-embedding culture systems, and that the inner layer cells have carbohydrates similar to those of conjunctival goblet cells. Culture of conjunctival epithelial cells within collagen gel is a useful model for examining differentiation of these cells.

Lectin and immunohistochemical comparison of glycoconjugates in the conjunctiva of patients with and without exfoliation syndrome

AIMS--The study was carried out to search for labelling similar to that of intraocular exfoliation material in the conjunctiva by light microscopy using lectin and immunohistochemistry. METHODS--Ten formalin fixed and paraffin embedded conjunctival biopsy specimens both from patients with and without exfoliation syndrome were studied with a panel of 11 lectins and with three monoclonal antibodies to the HNK-1 carbohydrate epitope, all of which react with intraocular exfoliation material. RESULTS--The lectin binding profile was essentially the same in specimens from patients with and without exfoliation syndrome. The superficial epithelium reacted similarly with Phaseolus vulgaris (PHA-E), Caragana arborescens (CAA), Helix pomatia (HPA), concanavalin A (ConA), and wheat germ (WGA) agglutinins. Binding was also detected with peanut (PNA) and Bauhinia purpurea (BPA) agglutinins, particularly in patients with exfoliation. The basement membrane generally reacted with Ricinus communis (RCA-I), PHA-E, Vicia villosa (VVA), ConA, and Lens culinaris (LCA) agglutinins. The stroma was weakly labelled with RCA-I, PHA-E, ConA, and LCA. Lectin binding to the vascular endothelium was moderate with RCA-I, PHA-E, CAA, ConA, LCA, and WGA. Inconsistent labelling was also detected with PNA, BPA, and Erythrina cristagalli agglutinin (ECA). The subendothelial region reacted weakly but consistently with PHA-E, ConA, and LCA, and inconsistently with PNA. Pretreatment with neuraminidase did not change that pattern. Antibodies to the HNK-1 epitope reacted only with myelinated stromal nerve branches. CONCLUSION--No evidence of abnormal deposits in any specimen was found. The carbohydrate composition of intraocular exfoliation material may differ from that of exfoliation-like fibres often detected in the conjunctiva by electron microscopy.

Galactose- binding sites in the acinar cells of the human accessory lacrimal gland

This investigation for the first time has collected evidence of a specific glycoconjugate contribution of the acinar cells from accessory lacrimal glands to human tears. Amongst group III lectin binding glycoconjugates, monosaccharides seem to be more prominent than disaccharides. alpha (and less obvious beta) Galactose sugar moieties appear to be specifically important. A need for further differentiating investigations is outlined.

Morphology and glycoconjugate histochemistry of the palpebral glands of the adult newt, Notophthalmus viridescens

The eyelids of the newt were studied in 10 microns serial paraffin and 1-2 microns plastic sections using standard histological stains and special stains for glycoconjugates. The eyelids contain four different glands. Simple acinar serous and simple acinar mucous glands occur in the skin; unicellular mucous glands occur in the conjunctiva; and convoluted tubular seromucous glands are present in connective tissue beneath the conjunctiva. The first two are identical to cutaneous glands found elsewhere on the head and body. The simple acinar serous glands are surrounded by myoepithelial cells and release their secretion, which is composed largely of proteins with minimal glycoconjugate content, by a holocrine mechanism. The secretory product of the simple acinar mucous glands is composed of neutral glycoconjugates with a minor content of acidic glycoconjugates; the mucin exhibits strong PAS and PAPD staining and weak staining by AB and PAPS methods. The unicellular conjunctival mucous glands secrete both neutral and acidic glycoconjugates as shown by positive reactions with PAS, PAPD, PAPS, and AB methods. Convoluted tubular seromucous glands in the ventral eyelid synthesize both proteins and neutral glycoconjugates. The mucous secretions of the conjunctival glands probably provide lubrication and protection for the cornea.

Ultrastructural localization of lectin-binding sites on the surface of the guinea pig conjunctival epithelium

The cell-surface binding sites of two lectins, concanavalin A (Con A) and wheat-germ agglutinin (WGA) in the guinea pig conjunctiva were investigated at the ultrastructural level by means of pre-embedding staining of the tissue with lectin-colloidal gold complexes. Wheat-germ agglutinin, which recognizes N-acetylglucosamine and sialic acid residues, showed prominent and fairly uniform binding to the microvilli. The binding was markedly increased in the vicinity of the goblet cells, indicating that the same carbohydrate ligands were also present in the mucus. In contrast, no binding of concanavalin A, which recognizes mannose and N-glucose, was observed. The results suggest the presence of sialic acid and galactose as the constituent carbohydrates of glycoconjugates in the surface membrane of conjunctival epithelial cells as well as in the mucus produced by the goblet cells.

Conjunctival cell glycoprotein pattern of healthy persons and of patients with primary Sjögren's syndrome--light microscopical investigation using lectin probes

Formalin-fixed biopsies of conjunctival tissue from the lower fornix of 10 healthy persons and of 10 patients with primary Sjögren's syndrome (primary SS) were examined by light microscopy. Deparaffinized, rehydrated sections of 5 microns were incubated overnight, each with one of 15 different biotinylated lectins. Bound lectins were visualized using avidin-HRP-substrate complexes. Five lectins did not bind to conjunctival cells, and further six lectins bound in an unspecific manner to conjunctival cells of both healthy persons and of primary SS patients. Jacalin lectin bound selectively to goblet cells of all specimens. Peanut agglutinin (PNA) and wheat germ agglutinin (WGA) bound significantly stronger to basal conjunctival epithelial cells of patients with primary SS. This binding pattern may be of diagnostic value.

Cellular carbohydrate components in human, rabbit and rat lacrimal gland. Studies using fluorescein and peroxidase labelled lectins

Orbital lacrimal glands from adult male and female rabbits, rats and humans were examined for the presence of intracellular receptors of four lectins: concanavalin-A agglutinin, lutus tetragonolobus agglutinin, ricinus comunis-60 agglutinin and wheat-germ agglutinin using fluorescein-conjugated lectin and peroxidase labelling methods for fluorescence and electron microscopy, respectively. Lectins were used as specific probes to detect carbohydrate moiety of the lacrimal gland. The pattern of labelling with the lectins suggests that N-acetyl-glucosamine, N-acetyl-D-galactosamine, D-galactose, D-mannose, sialic acid and L-fucose are contained in the lacrimal gland of the three species. The significance of these findings is discussed.

Lectin-cytochemical study on epithelial mucus glycoprotein of conjunctiva and pterygium

The epithelium of pterygium and conjunctiva was studied with reference to cytochemical reactivity to six fluorescein-labeled lectins that recognize a certain carbohydrate residue(s) of cellular membrane-bound or secretory glycoprotein: Ulex europaeus agglutinin-1 (UEA-1, specific for fucose); Dolichos biflorus agglutinin (DBA, specific for N-acetylgalactosamine); peanut agglutinin (PNA, specific for galactose-beta 1-3N-acetylgalactosamine): wheat germ agglutinin (WGA, specific for N-acetylglucosamine and N-acetylneuraminic acid); Concanavalia ensiformis (Con A, specific for mannose); Ricinus communis agglutinin-1 (RCA-1, specific for galactose). Non-goblet epithelial cells of pterygium were labeled with UEA-1, DBA and PNA, while those of conjunctiva were not. Distribution density of goblet cells was larger in pterygium than in conjunctiva, but there was no distinct difference in lectin reactivity between the two tissues, with marked label with WGA, PNA and RCA-1. Con A did not bind to either pterygium or conjunctiva. The observations suggest the presence of anomalous mucus glycoproteins secreted from pterygium.

Detection of ocular mucus in normal human conjunctiva and conjunctiva from patients with cicatricial pemphigoid using lectin probes and histochemical techniques

Conjunctival biopsies from patients with cicatricial pemphigoid affecting the conjunctiva and patients undergoing cataract surgery (normal conjunctiva) were snap-frozen, cryostat sectioned and incubated with fluorescein-conjugated lectins; peanut agglutinin (PNA), Helix pomatia agglutinin (HPA), soybean agglutinin (SBA), wheat germ agglutinin (WGA) and succinylated wheat germ agglutinin (S-WGA). Controls consisted of preincubating the lectins with the appropriate blocking sugars before applying the lectins to the sections. PNA and HPA stained the mucus granules contained in the conjunctival goblet cells but did not stain mucus or glycocalyx at the ocular surface distal to the goblet cells. Native WGA and S-WGA had high affinities for conjunctival goblet cells and the apical epithelial cell layers. Native WGA stained mucus and glycocalyx at the ocular surface. This staining of the ocular surface by WGA was confirmed at the transmission electron microscopic level using WGA conjugated to ferritin. Cicatricial pemphigoid patients in this study had reduced numbers of goblet cells; however, those goblet cells which were observed in cicatricial pemphigoid conjunctiva stained positively with HPA, PNA, WGA, and SWGA as did goblet cells in normal conjunctiva.

Detection of mucus glycoconjugates in human conjunctiva by using the lectin colloidal gold technique in TEM. I. A quantitative study in normal subjects

We applied a specific cytochemical reaction to characterize the glycoconjugates produced by goblet and non-goblet epithelial cells of normal human conjunctiva. For this purpose we utilized the lectins, proteins of vegetal origin, which are extremely sensitive in binding glycosidic residues. In particular, we used WGA, PNA, SBA and ConA conjugated with colloidal gold as ultrastructural marker for Transmission Electron Microscopy. This technique allowed us also to perform a quantitative analysis, by counting colloidal gold particles present on mucus granules. In this way we analyzed the content both of goblet and non-goblet epithelial cells. In the former, WGA, PNA, SBA and ConA receptors, here reported in decreasing density, were present. In the latter WGA was always positive, SBA and PNA sometimes were negative, ConA was always negative. We speculate the different contribution to mucus production by these two sources may be important in evaluating tear film stability alterations occurring in those diseases in which non-goblet epithelial cell vesicles increase.