Lectin binding to newt epidermis: fluorescent localization and effects on motility

The ability of seven lectins to bind to newt epidermal cells and influence their motility was examined. Of the seven fluoresceinated lectins applied to frozen sections containing intact newt skin and migrating epidermis (wound epithelium), only Con A (concanavalin A), WGA (wheat germ agglutinin), and PNA (peanut agglutinin) produced detectable epidermal fluorescence. Con A and WGA each heavily labeled all layers of intact epidermis, but PNA bound only to the more superficial layers. In contrast to a single population of labeled cells in migrating epidermal sheets after treatment with Con A, there were both labeled and unlabeled cells after exposure to either WGA or PNA. The wound bed was labeled by both Con A and WGA, but not by PNA. DBA (Dolichos bifloris agglutinin), RCA I (Ricinus communis agglutinin), and UEA (Ulex europaeus agglutinin), did not produce significant fluorescence with either migrating or intact epidermis. In general, inhibitory effects on epidermal motility correlated with the binding studies. Thus, Con A, WGA, and PNA, the lectins which clearly bound to the epidermis, all produced a concentration-dependent depression in the rate of epidermal wound closure. RCA was somewhat paradoxical in that it was moderately inhibitory despite showing essentially no binding. The effects of SBA and UEA were equivocal. DBA had no effect. These results indicate that the inhibition of motility produced by Con A that we have described previously is not peculiar to this mannose-binding lectin, but is shared by at least one lectin with an affinity for D-GlcNAc (WGA), and one with an affinity for B-D-Gal(1-3)-D-GalNAc (PNA).(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of lectin receptors in postimplantation mouse embryos at 6-8 days gestation

We have examined the pattern of binding of eleven lectins--BSL-II, WGA, LPA, Con A, DBA, SBA, LTA, UEA-I, MPA, PNA, and RCA-I, with specificity for a range of saccharides, to postimplantation mouse embryos from 6 to 8 days of gestation. The lectins were used to stain sections of ethanol-fixed paraffin-embedded and formaldehyde-fixed gelatin-embedded embryonic material. Our observations reveal a complex pattern of lectin binding to both cell surfaces and cytoplasm. Many of the lectins bind particularly to the outer surface of visceral endoderm (e.g., DBA, WGA, SBA, and RCA-I) and to the surface of the proamniotic cavity (e.g., RCA-I, PNA, and WGA). In the newly formed mesenchyme of primitive-streak-stage embryos, galactose and N-Ac-neuraminic acid are present but lectins with specificity for other sugars either did not bind to the cells or bound only in small amounts.     

Binding of lectins to human leukaemic cells

The interactions of five different lectins: peanut (PNA), lentil (LEN), wheat germ (WGA), soybean (SBA), Asparagus pea (FBP) with leukaemic cells obtained from 31 children: 25 with acute lymphoblastic leukaemia (ALL) and 6 with acute myeloblastic leukaemia (AML) were examined in this study. The relationship of lectin-binding ability to cells cytomorphological, cytochemical and immunological features and its potential clinical application were investigated. It has been shown that PNA and LEN receptors were found in the majority of blast cells. The SBA reacting cells were found only in few patients and FBP binding was not found in studied ALL and AML cells. There was a clear difference in the WGA binding capacity in ALL cells with L1 and L2 characteristics respectively. No differences were found in PNA. WGA and LEN reactivity between PAS negative and PAS positive leukaemic cells. Only PNA of all studied lectins seemed to differentiate T- from B-ALL blast cells. Only WGA binding of ALL cells showed the positive correlation to the risk index value.     

Lectin histochemistry of epidermal glandular cells in the earthworm Lumbricus terrestris (Annelida Oligochaeta)

Carbohydrate residues were localized in the glandular cells of the epidermis of Lumbricus terrestris by lectin histochemistry. The following biotinylated lectins were used: ConA, PNA, WGA, UEA-I. Each lectin has a specific binding pattern in the epidermal glandular cells. The ConA binding is evident in the orthochromatic mucous cells; PNA in the metachromatic mucous cells; WGA in the neuroendocrine-like cells; UEA-I in the cuticle. The epidermal glandular cells possess specific sites for the different lectins in relation to their functional characteristics. Therefore, these sugar residues indicate different behaviours of the cells in epidermal functions related to ion transport, receptor-secretory processes and defence.     

Fluorochrome-coupled lectins reveal distinct cellular domains in human epidermis

The distribution of saccharide moieties in human interfollicular epidermis was studied with fluorochrome-coupled lectins. In frozen sections Concanavalin A (Con A), Lens culinaris agglutinin (LCA), Ricinus communis agglutinin I (RCAI), and wheat germ agglutinin (WGA) stained intensively both dermis and viable epidermal cell layers, whereas peanut agglutinin (PNA) bound only to living epidermal cell layers. Ulex europaeus agglutinin I (UEAI) bound to dermal endothelial cells and upper cell layers of the epidermis but left the basal cell layer unstained. Dolichos biflorus agglutinin (DBA) bound only to basal epidermal cells, whereas both soybean agglutinin (SBA) and Helix pomatia agglutinin (HPA) showed strong binding to the spinous and granular cell layers. On routinely processed paraffin sections, a distinctly different staining pattern was seen with many lectins, and to reveal the binding of some lectins a pretreatment with protease was required. All keratin-positive cells in human epidermal cell suspensions, obtained with the suction blister method, bound PNA, whereas only a fraction of the keratinocytes bound either DBA or UEAI. Such a difference in lectin binding pattern was also seen in epidermal cell cultures both immediately after attachment and in organized cell colonies. This suggests that in addition to basal cells, more differentiated epidermal cells from the spinous cell layer are also able to adhere and spread in culture conditions. Gel electrophoretic analysis of the lectin-binding glycoproteins in detergent extracts of metabolically labeled primary keratinocyte cultures revealed that the lectins recognized both distinct and shared glycoproteins. A much different lectin binding pattern was seen in embryonic human skin: fetal epidermis did not show any binding of DBA, whereas UEAI showed diffuse binding to all cell layers but gave a bright staining of dermal endothelial cells. This was in contrast to staining results obtained with a monoclonal cytokeratin antibody, which showed the presence of a distinct basal cell layer in fetal epidermis also. The results indicate that expression of saccharide moieties in human epidermal keratinocytes is related to the stage of cellular differentiation, different cell layers expressing different terminal saccharide moieties. The results also suggest that the emergence of a mature cell surface glycoconjugate pattern in human epidermis is preceded by the acquisition of cell layer-specific, differential keratin expression.     

Lectin binding ability of B-chronic lymphocytic leukaemia cells.

The binding of five fluorescein-labelled lectins: peanut agglutinin (PNA), lentil agglutinin (LEN), soybean agglutinin (SBA), wheat germ agglutinin (WGA) and asparagus pea agglutinin (ASP) to human B-cell chronic lymphocytic leukaemia (B-CLL) and B lymphocytes of normal donors was studied. The specificity of the fluorescence was demonstrated by inhibition with appropriate saccharides. The proportion of B cells was estimated using anti-B cell monoclonal antibody. Both leukaemic and normal B cells showed the binding ability of all except of one (ASP) studied lectins. We have found the differences in surface carbohydrate patterns between B-CLL and normal B lymphocytes. B-CLL cells showed the considerably lower ability to bind SBA and slightly higher expression of PNA and LEN receptors in comparison to normal B cells. The analysis of WGA binding allowed for recognizing two groups of CLL patients: one with high and the second one with low WGA receptor expression. The double marker studies revealed that B cells could simultaneously react with anti-B cell monoclonal antibody and fluorochrome labelled lectins.     

Eosinophilic globule cells in mouse MFH-like sarcomas: lectin histochemistry.

Lectin binding patterns in ten mouse malignant fibrous histiocytoma (MFH)-like sarcomas containing eosinophilic globule (EG) cells and in granular metrial gland (GMG) cells of mouse placenta were stained with nine lectins (Con A, LCA, WGA, DBA, SBA, e-PHA, PNA, RCA-I and UEA-I) by an avidin-biotin-peroxidase-complex method. EG cells stained strongly with DBA, SBA and PNA which are specific for N-acetyl-D-galactosamine and/or D-galactose. DBA and SBA bound throughout the cytoplasm including the globules; PNA reacted preferentially at the cell surface. There was no evidence that these three lectins were reactive for immature EG cells. WGA, RCA-I and e-PHA also gave a slightly to moderately positive reaction to globules of EG cells. The results indicate that the globules contain abundant O-linked sequences of sugars, but also a few N-linked residues. MFH tumor cells showed a variable degree of binding with Con A, RCA-I, and WGA, but did not react with DBA, SBA and PNA. On the other hand, GMG cells exhibited specific affinities for DBA, SBA and PNA with staining patterns similar to those of EG cells. These findings suggest that EG and GMG cells may be of the same cellular lineage.     

Lectin binding to rat spermatogenic cells: Effects of different fixation methods and proteolytic enzyme treatment

Summary The binding of a panel of eight different fluorescein-conjugated lectins to rat spermatogenic cells was investigated. Particular attention was paid to the effects of different fixation methods and proteolytic enzyme digestion on the staining pattern.Concanavalin A (Con A), wheatgerm agglutinin (WGA), succinylated WGA (s-WGA) and agglutinin from gorse (UEA I) stained the cytoplasm of most germ cells as well as the spermatid acrosome. In contrast, peanut agglutinin (PNA), castor bean agglutinin (RCAI) and soy bean agglutinin (SBA) mainly stained the acrosome. The staining pattern varied depending on the fixation method used. PNA was particularly sensitive to formalin fixation, while SBA, DBA and UEA I showed decreased binding and Con A, WGA, s-WGA and RCA I were insensitive to this type of fixation. Pepsin treatment of the sections before lectin staining caused marked changes in the staining pattern; staining with PNA in formalin-fixed tissue sections was particularly improved but there was also enhanced staining with SBA and horse gram agglutinin (DBA). On the other hand, in Bouin- and particularly in acetone-fixed tissue sections, pepsin treatment decreased the staining with several of the lectins, for example WGA and UEA I.     

Spatial and temporal changes in the pattern of glycosylation of the developing chick limb tissue components as revealed by fluorescent conjugated lectin probes

The changing pattern of expression of glycoconjugates during the differentiation of the chick leg bud between stages 17 to 34 (days 3 to 8 of incubation) was studied using fluorochrome-labelled plant lectins. Limb buds were fixed in cold acetic-alcohol and wax-embedded. Agglutinins of peanut (PNA), soybean (SBA) and succinylated wheat germ (WGAs) revealed a specific binding pattern in the apical ectodermal ridge (AER) between Hamburger and Hamilton stages 19-32. These stages coincide with the period of elevation of the AER. This specific binding pattern was absent from the adjacent dorsal and ventral ectoderm. Prechondrogenic cells were positive for WGA and for PNA, and the PNA-binding capacity was intensified after neuraminidase treatment. Premyogenic cells at stage 23 can be identified as negative to PNA after neuraminidase, while the blood vessels became positive. PNA, SBA, WGA, WGAs and, in addition, Ricinus communis (RCA-I) lectins stained the basal membrane. Strands of extracellular matrix which connect with the basal membrane and cross the limb transversely between dorsal and ventral ectoderm were stained by RCA-I, SBA and PNA after neuraminidase.     

Cellular heterogeneity in normal human urothelium: Quantitative studies of lectin binding

Summary A panel of 10 FITC-labelled lectins (MPA, PNA, ConA, DBA, SBA, RCA-120, WGA, UEA, GS-I, GS-II) was applied to cryosections of seven specimens of normal urothelium. Seven of the lectins (MPA, ConA, RCA, WGA, UEA, GS-I and GS-II) showed a pattern of increasing fluorescence intensity from basal to superficial cells of the urothelium whereas PNA, DBA and SBA showed more uniform binding throughout the urothelium. Urothelial cell suspensions labelled with FITC-lectins were studied by flow cytometry to quantify the variation in binding to different cells types. Three cellular subpopulations were identified in normal urothelium on the basis of their optical properties. Fluorescence intensity due to specific lectin binding was then measured separately for each subpopulation. Although there was some variation among individual cases, a general pattern emerged in this small series. WGA, RCA, and GS-II bind in large quantities to all urothelial cells while PNA, SBA, ConA and DBA show little binding. MPA, RCA, UEA and GS-I showed the most marked increase in fluorescence intensity from basal to superficial cells as observed microscopically and quantified by flow cytometry.     

Glycoconjugates of human sperm surface. A study with fluorescent lectin conjugates and lens culinaris agglutinin affinity chromatography

Distribution of glycocompounds in human spermatozoa was studied by using fluorescent lectin-conjugates. Con A bound predominantly to acrosomal and posterior head regions whereas RCA I bound to the acrosomal region of intact spermatozoa, stained in suspension. Other lectins used (LCA, WGA, SBA, PNA) stained the the entire sperm surface. In airdried sperm smears binding of both Con A and RCA I were identical with the staining pattern obtained with living cells whereas LCA, WGA, SBA and PNA now bound heavily into acrosomal region. As a similar staining pattern was obtained with permeabilized sperm cells, this staining is apparently due to binding to intracellular structures. The efficiency of Lens culinaris agglutinin affinity chromatography in purification of human sperm glycoproteins was tested after their external radiolabelling with the neuraminidase/galactose oxidase/sodium borohydride method. 22% of applicated radioactivity could be eluted from the column with the specific inhibitory saccharide, and most of the radiolabelled surface glycoproteins of the whole sperm lysate, were also present in the LCA affinity column eluate. LCA affinity chromatography seems thus be an effective method to enrich membrane glycoproteins of human spermatozoa.     

Lectin binding pattern in normal human labial mucosa

Summary The pattern of lectin binding in normal human labial mucosa was examined by light and electron microscopy using eight different lectins (ConA, LCA, WGA, UEA-1, RCA-1, SBA, DBA and PNA) and compared with the patterns in normal human skin and oesophageal mucosa. As seen by light microscopy, ConA, LCA, and WGA stained cell membranes in all layers of the mucosae. RCA-1 stained the plasma membrane of cells in the basal and middle layers, whereas cells in the superficial layers showed little positive staining. UEA-1, SBA, and PNA stained the cells in the middle layers weakly in some cases. No positive staining for DBA was seen. By electron microscopy, reaction product indicating ConA-binding sites was observed in the plasma membrane, cisternae of the endoplasmic reticulum, nuclear envelope and the Golgi apparatus. Binding of LCA, WGA, and RCA-1 was observed in the plasma membrane. These results show that the binding pattern of PNA, SBA, and RCA-1 in labial mucosa is different from that in the normal skin or oesophageal mucosa, although the labial mucosal epithelium, epidermis, and oesophageal epithelium are all stratified squamous epithelia. These differences in the cell-surface sugar residues are likely to be related to the possible functional differences in these tissues.     

Kinetoplastid flagellates: surface-reactive carbohydrates detected by fluorescein-conjugated lectins

Membrane-associated carbohydrate residues of 3 isolates of Leishmania derived from etiological agents of visceral leishmaniasis (VL), postkala-azar dermal leishmaniasis (PKDL), and cutaneous leishmaniasis (CL), as well as 2 other nonpathogenic insect gut kinetoplastid flagellates, Bodo sp. and Herpetomonas sp., were characterized with the aid of 8 fluorescein-conjugated lectins. Four lectins, concanavalin A, Dolichos biflorus, phytohemagglutinin P, Ricinus communis agglutinin, bound to all kinetoplastid flagellates at different concentrations. All Leishmania promastigotes showed reactions with Ulex agglutinin. Although these lectins were bound to all kinetoplastids, the site and intensity of binding was different. All skin-dwelling Leishmania parasites, viz., Leishmania donovani of PKDL and Leishmania tropica of CL showed unique selectivity toward peanut agglutinin (PNA), soybean agglutinin, and wheatgerm agglutinin (WGA). More interestingly, Herpetomonas showed positive fluorescence with PNA and WGA, whereas Bodo was negative. The results demonstrated that no lectin could distinguish between the pathogenic and nonpathogenic status of kinetoplastid flagellates. Moreover, the antigenic (carbohydrate) profiles of Herpetomonas corresponded more closely to those of L. tropica, whereas Bodo shared some common lectin receptors with L. donovani of VL.     

Effects of plant lectins on the adhesive properties of baby hamster kidney cells

We studied the effects of different lectins on the adhesive properties of baby hamster kidney (BHK) cells. The purpose of these studies was to learn more about the cell surface receptors involved in cell adhesion. Three adhesive phenomena were analyzed: 1) the adhesion of BHK cells to lectin-coated substrata; 2) the effects of lectins on the adhesion of cells to substrata coated by plasma fibronectin (pFN); and 3) the effects of lectins on the binding of pFN-coated beads to cells. Initial experiments with fluorescein-conjugated lectins indicated that concanavalin A (Con A), ricinus communis agglutinin I (RCA I), and wheat germ agglutinin (WGA) bound to BHK cells but peanut agglutinin (PNA), soybean agglutinin (SBA), and ulex europaeus agglutinin I (UEA I) dod not bind. All three of the lectins which bound to the cells promoted cell spreading on lectin substrata, and the morphology of the spread cells was similar to that observed with cells spread on pFN substrata. Protease treatment of the cells, however, was found to inhibit cell spreading on pFN substrata or WGA substrata more than on Con A substrata or RCA I substrata. In the experiment of cells with Con A or WGA inhibited cell spreading on pFN substrata, but RCA I treatment had no effect. Finally, treatment of cells with WGA inhibited binding to cells of pFN beads, but neither Con A nor RCA I affected this interaction. These results indicate that the lectins modify cellular adhesion in different ways, probably by interacting with different surface receptors. The possibility that the pFN receptor is a WGA receptor is discussed.     

Developmental changes in the heterocellular epidermis of Pelobates syriacus integument.

Changes in characteristic components of the skin epidermis of the large tadpole of Pelobates syriacus were studied throughout its development. The fate of two specific cells in the skin epidermis was followed, from the young tadpole to the adult was studied. It was found that flask-shaped type cells in the tadpole epidermis which are PAS-positive, stain with peanut lectin (PNA). There is no detectable band 3 in the premetamorphosed stages, and mitochondria-rich cells are very rare. This pattern of staining changes completely upon metamorphosis: the PAS-positive cells, specific to the tadpole epidermis disappear, and the mitochondria-rich (MR) cells in the adult skin epithelium react with polyclonal anti-band 3 antibody. Western blot analysis showed the presence of a band 3-like protein of about 95 kDa, only in the adult epithelial extract, corroborating the immunocytochemical observations. The finding of the presence of band 3-like protein in the MR cells of Pelobates, is similar to the observations made in the skin of other amphibian species. On the other hand, the binding of peanut lectin to MR cells is species-specific, since it does not react with the MR cells in the skin epithelium of Pelobates syriacus.     

Lectin-binding pattern of neuroepithelial and respiratory epithelial cells in the mouse nasal cavity

Summary Sections from the nasal cavity of 12-day-old Swiss albino mice (NMRI strain) were subjected to lectin histochemistry. A panel of biotinylated lectins (Con A, WGA, s-WGA, PNA, SBA, DBA and UEA I) and a horseradish peroxidase-conjugated lectin (GSA II) showed marked differences in binding to the respiratory and the neuroepithelial cells. SBA (affinity for galactose andN-acetylgalactosamine), PNA (galactose) and WGA (sialic acids andN-acetylglucosamine) labelled the receptor neurons in the olfactory and vomeronasal epithelium. DBA (N-acetylgalactosamine) labelled a subgroup of about 5% of the olfactory receptor neurons, but most neurons in the vomeronasal organ. UEA I (fucose) and s-WGA (N-acetylglucosamine) intensely labelled the entire nerve cell population in the vomeronasal organ, but in the olfactory epithelium the labelling with these lectins was stratified. In the respiratory epithelium the ciliated cells were labelled with WGA and s-WGA, while the secretory cells bound most of the lectins. Thus different sugars are exposed on the surface of the different types of epithelia in the nasal cavity, providing a basis for selectivity in microbial attacks on these areas.     

Changes in lectin-binding pattern in the digestive tract of Xenopus laevis during metamorphosis. II. Small intestine.

The binding of seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin, UEA-I; and wheat germ agglutinin, WGA) to the small intestine in metamorphosing Xenopus laevis was studied by the avidin-biotin-peroxidase (ABC) method. The staining pattern of the epithelium with all lectins except for UEA-I and Con A changed gradually during metamorphic climax; the main component of the epithelium, absorptive cells, gradually became positive for DBA, PNA, and SBA and the scattered goblet cells for RCA-I and WGA. On the other hand, the change of the staining pattern in the connective tissue occurred only for Con A, RCA-I, and WGA, and this change took place rapidly at the beginning of climax (stage 60). Increased staining for Con A and WGA at stage 60 was observed only in a group of connective tissue cells close to the epithelium and in the basement membrane. As metamorphosis progressed, this localization of the staining intensity became less clear. At the completion of metamorphosis (stage 66), the absorptive cells were stained with all lectins except for UEA-I, whereas the goblet cells stained only with RCA-I and WGA. These results indicate that lectin histochemistry can distinguish between larval and adult cells of both two epithelial types (absorptive and goblet cells). The technique may also identify a group of connective tissue cells, close to the epithelium, that possibly induce the metamorphic epithelial changes.     

Binding of fluorescent lectins to the surface of germ cells from fetal and early postnatal mouse gonads

Fluorescent lectins were used to study the chemical nature of carbohydrate moieties present on the surface of female and male germ cells isolated from mouse gonads during fetal and early posnatal development. Concanavalin A (ConA), lens culinaris agglutinin (LCA), ricinus communis agglutinin (RCA_I) and wheat germ agglutinin (WGA) bound intensely to the germ cell plasma membrane at all stages studied. Other lectins such as ulex europaeus agglutinin (UEA_I) and agglutinin (SBA) did not bind or bound moderately (SBA to female germ cells only). Distinct developmental-related changes were observed when female germ cells were labeled with fluorescein-conjugated peanut agglutinin (PNA) or dolichos biflorus agglutinin (DBA). DBA and PNA binding was absent or weak in fetal female and male germ cells, but became intensely positive in oocytes in the immediate postnatal period. The percentage of oocytes stained with DBA increased during the first three days after birth, and from day 3–4 onwards all oocytes were strongly labeled. I suggest that these changes in lectin binding reflect changes in biochemical structure of the oocyte surface related to differentiative events occurring in the mouse ovary immediately after birth.     

A comparison of lectin binding in rat and human peripheral nerve

Eleven different fluorescein- or peroxidase-conjugated lectins with different sugar-binding affinities were employed to analyze and compare glycoconjugates of rat and human peripheral nerves at the light microscopic level. A majority of lectins showed a distinct binding pattern in different structures of the nerve. Lectin binding was similar but not identical in rat and human nerves. Limulus polyhemus agglutinin did not stain any structures in rat or human nerves. In both species, all other lectins bound to the perineurium. Perineurial staining was intense with Canavalia ensiformis (Con A), Triticum vulgaris (WGA), Maclura pomifera (MPA); moderate with Glycine max (SBA), Griffonia simplicifolia-I (GS-I) and GS-II; weak with Ulex europaeus (UEA), Dolichos biflorus (DBA), and Ricinus communis (RCA). In the endoneurium of both species, ConA staining was intense, MPA and WGA moderate, SBA, GS-II, PNA, and RCA weak, and UEA and DBA absent. Interestingly, GS-I stained rat but not human endoneurium. Most lectins bound to blood vessels. GS-I bound to rat but not human, whereas UEA bound to human but not rat vessels. The results show that lectins can be used to reveal heterogeneity in sugar residues of glycoconjugates within neural and vascular components of nerves. They may therefore be potentially useful in detecting changes in glycoconjugates during nerve degeneration and subsequent regeneration after trauma or in pathological states.     

Histochemical study of rabbit duodenal mucosa carried out using lectins

The Authors report histochemical findings about rabbit's duodenal mucosa. The present study has been carried out using five different lectins (Peanut Agglutinin (PNA), Dolichos Biflorus Agglutinin (DBA), Wheat Germ Agglutinin (WGA), Soybean Agglutinin (SBA), Ulex Europaeus Agglutinin I (UEA-I). These lectins have been labelled with Horseradish Peroxidase and binding sites have been stained with 3-3' Diaminobenzidine, according to Farragiana et al. The PNA reacted with the glandular cells, while the reaction was negative in the superficial cells. The DBA reacted exclusively with the glandular cells. The superficial and the glandular cells showed strong positive binding sites to the WGA and slight positive binding sites to the SBA. The UEA-I did not react with the epithelial cells. The presence of binding sites for the lectins we have used in the present study, shows a different glycoprotein composition of the cellular secretion, in comparison with the other animals we have already studied. In addition, these lectins can not be used as cellular differentiation markers in the epithelial cells of the rabbit's duodenal mucosa.