A distinct class of vesicles derived from the trans-Golgi mediates secretion of xylogalacturonan in the root border cell.

Root border cells lie on the surface of the root cap and secrete massive amounts of mucilage that contains polysaccharides and proteoglycans. Golgi stacks in the border cells have hypertrophied margins, reflecting elevated biosynthetic activity to produce the polysaccharide components of the mucilage. To investigate the three-dimensional structures and macromolecular compositions of these Golgi stacks, we examined high-pressure frozen/freeze-substituted alfalfa root cap cells with electron microscopy/tomography. Golgi stacks in border cells and peripheral cells, precursor cells of border cells, displayed similar morphological features, such as proliferation of trans cisternae and swelling of the trans cisternae and trans-Golgi network (TGN) compartments. These swollen margins give rise to two types of vesicles larger than other Golgi-associated vesicles. Margins of trans-Golgi cisternae accumulate the LM8 xylogalacturonan (XGA) epitope, and they become darkly stained large vesicles (LVs) after release from the Golgi. Epitopes for xyloglucan (XG), polygalacturonic acid/rhamnogalacturonan-I (PGA/RG-I) are detected in the trans-most cisternae and TGN compartments. LVs produced from TGN compartments (TGN-LVs) stained lighter than LVs and contained the cell wall polysaccharide epitopes seen in the TGN. LVs carrying the XGA epitope fuse with the plasma membrane only in border cells, whereas TGN-LVs containing the XG and PGA/RG-I epitopes fuse with the plasma membrane of both peripheral cells and border cells. Taken together, these results indicate that XGA is secreted by a novel type of secretory vesicles derived from trans-Golgi cisternae. Furthermore, we simulated the collapse in the central domain of the trans-cisternae accompanying polysaccharide synthesis with a mathematical model.

Cotton fiber tips have diverse morphologies and show evidence of apical cell wall synthesis.

Cotton fibers arise through highly anisotropic expansion of a single seed epidermal cell. We obtained evidence that apical cell wall synthesis occurs through examining the tips of young elongating Gossypium hirsutum (Gh) and G. barbadense (Gb) fibers. We characterized two tip types in Gh fiber (hemisphere and tapered), each with distinct apical diameter, central vacuole location, and distribution of cell wall components. The apex of Gh hemisphere tips was enriched in homogalacturonan epitopes, including a relatively high methyl-esterified form associated with cell wall pliability. Other wall components increased behind the apex including cellulose and the α-Fuc-(1,2)-ß-Gal epitope predominantly found in xyloglucan. Gb fibers had only one narrow tip type featuring characters found in each Gh tip type. Pulse-labeling of cell wall glucans indicated wall synthesis at the apex of both Gh tip types and in distal zones. Living Gh hemisphere and Gb tips ruptured preferentially at the apex upon treatment with wall degrading enzymes, consistent with newly synthesized wall at the apex. Gh tapered tips ruptured either at the apex or distantly. Overall, the results reveal diverse cotton fiber tip morphologies and support primary wall synthesis occurring at the apex and discrete distal regions of the tip.

Adjuvant properties of water extractable arabinoxylans with different structural features from wheat flour against model antigen ovalbumin.

Despite the numerous benefits of AX on the immune system and gut bacteria, the potential adjuvant activity of WEAX on immune responses has not been adequately investigated. In the present study, three kinds of WEAX with different structural features were obtained and their adjuvant potential on the specific cellular and humoral immune responses in ovalbumin (OVA) immunized mice were assessed. Our data demonstrated that WEAX had potent effects on innate and acquired immune responses through up-regulating the NK cell activation and promoting the Th2 type immune response. Furthermore, this study also elucidated the possible relationship between the adjuvant activity of WEAX and the structure. Compared with the other characteristics of the WEAX, we found that the immunomodulatory activity may be related to their content of ferulic acid, and not to the molecular weight.

Arabinoxylan activates Dectin-1 and modulates particulate ß-glucan-induced Dectin-1 activation.

SCOPE: Arabinoxylan is one of the most commonly consumed dietary fiber. Immunomodulation by arabinoxylan is documented but the mechanisms by which these immune-effects are accomplished are unknown. METHODS AND RESULTS: By applying reporter cell lines for Toll-like receptors (TLRs) and Dectin-1, we demonstrated that arabinoxylan interacts with Dectin-1 receptors and not with TLRs. Arabinoxylan activates Dectin-1 to a similar magnitude as soluble ß-glucans. Soluble ß-glucans are known to inhibit the particulate ß-glucan-induced activation of Dectin-1. As arabinoxylan is also soluble, the inhibiting capacity of arabinoxylan on particulate ß-glucan-activated Dectin-1 cell lines was studied. It was found that this inhibition was similar to that of soluble ß-glucan and was caused predominantly by inhibition of the Dectin-1A transcript variant. The Dectin-1 inhibitory function of arabinoxylan was further confirmed in human dendritic cells that demonstrated reduced production of IL-10 and TNF-α. The production of the antifungal cytokines IL-4 and IL-23 were increased in dendritic cells stimulated with arabinoxylan and particulate ß-glucan. In contrast to soluble ß-glucan, arabinoxylan did not enhance production of IL-10, TNF-α, and IL-23. CONCLUSION: Arabinoxylan activates Dectin-1 and supports antifungal immune responses in human dendritic cells. The mode of action of arabinoxylan is similar but not identical to that of soluble ß-glucans.

Structure-function relationships of immunostimulatory polysaccharides: A review.

Immunostimulatory polysaccharides are compounds capable of interacting with the immune system and enhance specific mechanisms of the host response. Glucans, mannans, pectic polysaccharides, arabinogalactans, fucoidans, galactans, hyaluronans, fructans, and xylans are polysaccharides with reported immunostimulatory activity. The structural features that have been related with such activity are the monosaccharide and glycosidic-linkage composition, conformation, molecular weight, functional groups, and branching characteristics. However, the establishment of structure-function relationships is possible only if purified and characterized polysaccharides are used and selective structural modifications performed. Aiming at contributing to the definition of the structure-function relationships necessary to design immunostimulatory polysaccharides with potential for preventive or therapeutical purposes or to be recognized as health-improving ingredients in functional foods, this review introduces basic immunological concepts required to understand the mechanisms that rule the potential claimed immunostimulatory activity of polysaccharides and critically presents a literature survey on the structural features of the polysaccharides and reported immunostimulatory activity.

Automated synthesis of arabinoxylan-oligosaccharides enables characterization of antibodies that recognize plant cell wall glycans.

Monoclonal antibodies that recognize plant cell wall glycans are used for high-resolution imaging, providing important information about the structure and function of cell wall polysaccharides. To characterize the binding epitopes of these powerful molecular probes a library of eleven plant arabinoxylan oligosaccharides was produced by automated solid-phase synthesis. Modular assembly of oligoarabinoxylans from few building blocks was enabled by adding (2-naphthyl)methyl (Nap) to the toolbox of orthogonal protecting groups for solid-phase synthesis. Conjugation-ready oligosaccharides were obtained and the binding specificities of xylan-directed antibodies were determined on microarrays.

Relative deposition of xylan and 8-5'-linked lignin structure in Chamaecyparis obtusa, as revealed by double immunolabeling by using monoclonal antibodies.

MAIN CONCLUSION: Immunolabeling by using monoclonal antibodies showed that xylan deposition precedes the formation of 8-5'-linked structure of lignin in normal and compression woods of Chamaecyparis obtusa. Xylan deposition and formation of 8-5'-linked lignin structure in differentiating xylems from normal and compression woods in Chamaecyparis obtusa were examined by immunoelectron microscopy using monoclonal antibodies (LM10 or LM11) to detect xylan localization. The 8-5'-linked lignin structure was immunolocalized using KM1 antibody. Xylan and 8-5'-linked lignin double immunolabeling was performed using secondary antibodies labeled with colloidal gold particles of different diameters. In normal wood, KM1 labeling occurred in the compound middle lamella (CML) and S1 layer during S1 layer formation and increased as S2 and S3 layers formed, with labeling occurring at the outer part of the previous layer. In compression wood, mild KM1 labeling occurred in the CML and outer part of the S1 layer at the later S1 layer formation stage, with increased labeling as the S2 layer formed. Minor labeling occurred in the outer part of the S2 layer during helical cavity formation. Comparison between KM1 labeling and KMnO4 staining suggested that lignin other than 8-5'-linked structure was formed during early lignification, and the proportion of 8-5'-linked lignin structure increased at later stages of lignification in both normal and compression woods. LM10 and LM11 labeling occurred slightly earlier than KM1 labeling, suggesting that xylan deposition preceded the formation of 8-5'-linked lignin in normal and compression woods. Less labeling by KM1, LM10, and LM11 occurred in the outer part of the S2 layer in compression wood, which has abundant lignin. Thus, lignin in these parts is composed of lignin substructures other than the 8-5' linkage.

Arrangement of mixed-linkage glucan and glucuronoarabinoxylan in the cell walls of growing maize roots.

BACKGROUND AND AIMS: Plant cell enlargement is unambiguously coupled to changes in cell wall architecture, and as such various studies have examined the modification of the proportions and structures of glucuronoarabinoxylan and mixed-linkage glucan in the course of cell elongation in grasses. However, there is still no clear understanding of the mutual arrangement of these matrix polymers with cellulose microfibrils and of the modification of this architecture during cell growth. This study aimed to determine the correspondence between the fine structure of grass cell walls and the course of the elongation process in roots of maize (Zea mays). METHODS: Enzymatic hydrolysis followed by biochemical analysis of derivatives was coupled with immunohistochemical detection of cell wall epitopes at different stages of cell development in a series of maize root zones. KEY RESULTS: Two xylan-directed antibodies (LM11 and ABX) have distinct patterns of primary cell wall labelling in cross-sections of growing maize roots. The LM11 epitopes were masked by mixed-linkage glucan and were revealed only after lichenase treatment. They could be removed from the section by xylanase treatment. Accessibility of ABX epitopes was not affected by the lichenase treatment. Xylanase treatment released only part of the cell wall glucuronoarabinoxylan and produced two types of products: high-substituted (released in polymeric form) and low-substituted (released as low-molecular-mass fragments). The amount of the latter was highly correlated with the amount of mixed-linkage glucan. CONCLUSIONS: Three domains of glucuronoarabinoxylan were determined: one separating cellulose microfibrils, one interacting with them and a middle domain between the two, which links them. The middle domain is masked by the mixed-linkage glucan. A model is proposed in which the mixed-linkage glucan serves as a gel-like filler of the space between the separating domain of the glucuronoarabinoxylan and the cellulose microfibrils. Space for glucan is provided along the middle domain, the proportion of which increases during cell elongation.

Arabinogalactan protein-rich cell walls, paramural deposits and ergastic globules define the hyaline bodies of rhinanthoid Orobanchaceae haustoria.

BACKGROUND AND AIMS: Parasitic plants obtain nutrients from their hosts through organs called haustoria. The hyaline body is a specialized parenchymatous tissue occupying the central parts of haustoria in many Orobanchaceae species. The structure and functions of hyaline bodies are poorly understood despite their apparent necessity for the proper functioning of haustoria. Reported here is a cell wall-focused immunohistochemical study of the hyaline bodies of three species from the ecologically important clade of rhinanthoid Orobanchaceae. METHODS: Haustoria collected from laboratory-grown and field-collected plants of Rhinanthus minor, Odontites vernus and Melampyrum pratense attached to various hosts were immunolabelled for cell wall matrix glycans and glycoproteins using specific monoclonal antibodies (mAbs). KEY RESULTS: Hyaline body cell wall architecture differed from that of the surrounding parenchyma in all species investigated. Enrichment in arabinogalactan protein (AGP) epitopes labelled with mAbs LM2, JIM8, JIM13, JIM14 and CCRC-M7 was prominent and coincided with reduced labelling of de-esterified homogalacturonan with mAbs JIM5, LM18 and LM19. Furthermore, paramural bodies, intercellular deposits and globular ergastic bodies composed of pectins, xyloglucans, extensins and AGPs were common. In Rhinanthus they were particularly abundant in pairings with legume hosts. Hyaline body cells were not in direct contact with haustorial xylem, which was surrounded by a single layer of paratracheal parenchyma with thickened cell walls abutting the xylem. CONCLUSIONS: The distinctive anatomy and cell wall architecture indicate hyaline body specialization. Altered proportions of AGPs and pectins may affect the mechanical properties of hyaline body cell walls. This and the association with a transfer-like type of paratracheal parenchyma suggest a role in nutrient translocation. Organelle-rich protoplasts and the presence of exceptionally profuse intra- and intercellular wall materials when attached to a nitrogen-fixing host suggest subsequent processing and transient storage of nutrients. AGPs might therefore be implicated in nutrient transfer and metabolism in haustoria.

Mutations in multiple XXT genes of Arabidopsis reveal the complexity of xyloglucan biosynthesis.

Xyloglucan is an important hemicellulosic polysaccharide in dicot primary cell walls. Most of the enzymes involved in xyloglucan synthesis have been identified. However, many important details of its synthesis in vivo remain unknown. The roles of three genes encoding xylosyltransferases participating in xyloglucan biosynthesis in Arabidopsis (Arabidopsis thaliana) were further investigated using reverse genetic, biochemical, and immunological approaches. New double mutants (xxt1 xxt5 and xxt2 xxt5) and a triple mutant (xxt1 xxt2 xxt5) were generated, characterized, and compared with three single mutants and the xxt1 xxt2 double mutant that had been isolated previously. Antibody-based glycome profiling was applied in combination with chemical and immunohistochemical analyses for these characterizations. From the combined data, we conclude that XXT1 and XXT2 are responsible for the bulk of the xylosylation of the glucan backbone, and at least one of these proteins must be present and active for xyloglucan to be made. XXT5 plays a significant but as yet uncharacterized role in this process. The glycome profiling data demonstrate that the lack of detectable xyloglucan does not cause significant compensatory changes in other polysaccharides, although changes in nonxyloglucan polysaccharide amounts cannot be ruled out. Structural rearrangements of the polysaccharide network appear responsible for maintaining wall integrity in the absence of xyloglucan, thereby allowing nearly normal plant growth in plants lacking xyloglucan. Finally, results from immunohistochemical studies, combined with known information about expression patterns of the three genes, suggest that different combinations of xylosyltransferases contribute differently to xyloglucan biosynthesis in the various cell types found in stems, roots, and hypocotyls.

Substituent-specific antibody against glucuronoxylan reveals close association of glucuronic acid and acetyl substituents and distinct labeling patterns in tree species.

Immunolabeling can be used to locate plant cell wall carbohydrates or other components to specific cell types or to specific regions of the wall. Some antibodies against xylans exist; however, many partly react with the xylan backbone and thus provide limited information on the type of substituents present in various xylans. We have produced a monoclonal antibody which specifically recognizes glucopyranosyl uronic acid (GlcA), or its 4-O-methyl ether (meGlcA), substituents in xylan and has no cross-reactivity with linear or arabinofuranosyl-substituted xylans. The UX1 antibody binds most strongly to (me)GlcA substitutions at the non-reducing ends of xylan chains, but has a low cross-reactivity with internal substitutions as well, at least on oligosaccharides. The antibody labeled plant cell walls from both mono- and dicotyledons, but in most tissues an alkaline pretreatment was needed for antibody binding. The treatment removed acetyl groups from xylan, indicating that the vicinity of glucuronic acid substituents is also acetylated. The novel labeling patterns observed in the xylem of tree species suggested that differences within the cell wall exist both in acetylation degree and in glucuronic acid content.

Spatial and temporal variability of xylan distribution in differentiating secondary xylem of hybrid aspen.

Xylans occupy approximately one-third of the cell wall components in hardwoods and their chemical structures are well understood. However, the microdistribution of xylans (O-acetyl-4-O-methylglucuronoxylans, AcGXs) in the cell wall and their correlation with functional properties of cells in hardwood xylem is poorly understood. We demonstrate here the spatial and temporal distribution of xylans in secondary xylem cells of hybrid aspen using immunolocalization with LM10 and LM11 antibodies. Xylan labeling was detected earliest in fibers at the cell corner of the S1 layer, and then later in vessels and ray cells respectively. Fibers showed a heterogeneous labeling pattern in the mature cell wall with stronger labeling of low substituted xylans (lsAcGXs) in the outer than inner cell wall. In contrast, vessels showed uniform labeling in the mature cell wall with stronger labeling of lsAcGXs than fibers. Xylan labeling in ray cells was detected much later than that in fibers and vessels, but was also detected at the beginning of secondary cell wall formation as in fibers and vessels with uniform labeling in the cell wall regardless of developmental stage. Interestingly, pit membranes including fiber-, vessel- and ray-vessel pits showed strong labeling of highly substituted xylans (hsAcGXs) during differentiation, although this labeling gradually disappeared during pit maturation. Together our observations indicate that there are temporal and spatial variations of xylan deposition and chemical structure of xylans between cells in aspen xylem. Differences in xylan localization between aspen (hardwood) and cedar (softwood) are also discussed.

Heterogeneous distribution of pectin epitopes and calcium in different pit types of four angiosperm species.

Intervessel pits act as safety valves that prevent the spread of xylem embolism. Pectin-calcium crosslinks within the pit membrane have been proposed to affect xylem vulnerability to cavitation. However, as the chemical composition of pit membranes is poorly understood, this hypothesis has not been verified. Using electron microscopy, immunolabeling, an antimonate precipitation technique, and ruthenium red staining, we studied the distribution of selected polysaccharides and calcium in the pit membranes of four angiosperm tree species. We tested whether shifts in xylem vulnerability resulting from perfusion of stems with a calcium chelating agent corresponded with the distribution of pectic homogalacturonans (HG) and/or calcium within interconduit pit membranes. No HG were detected in the main part of intervessel pit membranes, but were consistently found in the marginal membrane region known as the annulus. Calcium colocalized with HG in the annulus. In contrast to intervessel pits, the membrane of vessel-ray pits showed a high pectin content. The presence of two distinct chemical domains, the annulus and the actual pit membrane, can have substantial implications for pit membrane functioning. We propose that the annulus could affect the observed shift in xylem vulnerability after calcium removal by allowing increased pit membrane deflection.

Immunomodulatory activity of dietary fiber: arabinoxylan and mixed-linked beta-glucan isolated from barley show modest activities in vitro.

High intake of dietary fiber is claimed to protect against development of colorectal cancer. Barley is a rich source of dietary fiber, and possible immunomodulatory effects of barley polysaccharides might explain a potential protective effect. Dietary fiber was isolated by extraction and enzyme treatment. A mixed-linked ß-glucan (WSM-TPX, 96.5% ß-glucan, Mw 886 kDa), an arabinoxylan (WUM-BS-LA, 96.4% arabinoxylan, Mw 156 kDa), a mixed-linked ß-glucan rich fraction containing 10% arabinoxylan (WSM-TP) and an arabinoxylan rich fraction containing 30% mixed-linked ß-glucan (WUM-BS) showed no significant effect on IL-8 secretion and proliferation of two intestinal epithelial cell lines, Caco-2 and HT-29, and had no significant effect on the NF-κB activity in the monocytic cell line U937-3κB-LUC. Further enriched arabinoxylan fractions (WUM-BS-LA) from different barley varieties (Tyra, NK96300, SB94897 and CDCGainer) were less active than the mixed-linked ß-glucan rich fractions (WSM-TP and WSM-TPX) in the complement-fixing test. The mixed-linked ß-glucan rich fraction from NK96300 and CDCGainer showed similar activities as the positive control while mixed-linked ß-glucan rich fractions from Tyra and SB94897 were less active. From these results it is concluded that the isolated high molecular weight mixed-linked ß-glucans and arabinoxylans from barley show low immunological responses in selected in vitro test systems and thus possible anti-colon cancer effects of barley dietary fiber cannot be explained by our observations.

Inhibition of degranulation and cytokine production in bone marrow-derived mast cells by hydrolyzed rice bran.

OBJECTIVE: We investigated the effects of hydrolyzed rice bran (HRB), an arabinoxylan extracted from rice bran, on mast cell degranulation and cytokine production. MATERIALS AND METHODS: HRB was obtained by treating rice bran with an extract obtained from shiitake mushrooms. Bone marrow-derived mast cells (BMMCs) were prepared by culturing bone marrow cells from BALB/c mice in the presence of interleukin-3 and stem cell factor for 4 weeks. BMMCs were pretreated with HRB (0-3 mg/ml) for 30 min and were then antigen activated. RESULTS: Pretreatment of BMMCs with HRB significantly inhibited antigen-induced degranulation and cytokine production (tumor necrosis factor-alpha and interleukin-4) in a dose-dependent manner. HRB also diminished membrane fusion between liposomes in which soluble N-ethyl maleimide-sensitive factor attachment protein receptors were reconstituted. Phosphorylation of RelA and mitogen-activated kinases after antigen stimulation was suppressed by pretreatment of BMMCs with HRB. CONCLUSIONS: These findings suggest that HRB may have an anti-inflammatory effect by inhibiting mast cell degranulation and cytokine production.

Pectic homogalacturonan masks abundant sets of xyloglucan epitopes in plant cell walls.

BACKGROUND: Molecular probes are required to detect cell wall polymers in-situ to aid understanding of their cell biology and several studies have shown that cell wall epitopes have restricted occurrences across sections of plant organs indicating that cell wall structure is highly developmentally regulated. Xyloglucan is the major hemicellulose or cross-linking glycan of the primary cell walls of dicotyledons although little is known of its occurrence or functions in relation to cell development and cell wall microstructure. RESULTS: Using a neoglycoprotein approach, in which a XXXG heptasaccharide of tamarind seed xyloglucan was coupled to BSA to produce an immunogen, we have generated a rat monoclonal antibody (designated LM15) to the XXXG structural motif of xyloglucans. The specificity of LM15 has been confirmed by the analysis of LM15 binding using glycan microarrays and oligosaccharide hapten inhibition of binding studies. The use of LM15 for the analysis of xyloglucan in the cell walls of tamarind and nasturtium seeds, in which xyloglucan occurs as a storage polysaccharide, indicated that the LM15 xyloglucan epitope occurs throughout the thickened cell walls of the tamarind seed and in the outer regions, adjacent to middle lamellae, of the thickened cell walls of the nasturtium seed. Immunofluorescence analysis of LM15 binding to sections of tobacco and pea stem internodes indicated that the xyloglucan epitope was restricted to a few cell types in these organs. Enzymatic removal of pectic homogalacturonan from equivalent sections resulted in the abundant detection of distinct patterns of the LM15 xyloglucan epitope across these organs and a diversity of occurrences in relation to the cell wall microstructure of a range of cell types. CONCLUSION: These observations support ideas that xyloglucan is associated with pectin in plant cell walls. They also indicate that documented patterns of cell wall epitopes in relation to cell development and cell differentiation may need to be re-considered in relation to the potential masking of cell wall epitopes by other cell wall components.

Monoclonal antibodies to plant cell wall xylans and arabinoxylans.

Two rat monoclonal antibodies have been generated to plant cell wall (1-->4)-beta-D-xylans using a penta-1,4-xylanoside-containing neoglycoprotein as an immunogen. The monoclonal antibodies, designated LM10 and LM11, have different specificities to xylans in relation to the substitution of the xylan backbone as indicated by immunodot assays and competitive-inhibition ELISAs. LM10 is specific to unsubstituted or low-substituted xylans, whereas LM11 binds to wheat arabinoxylan in addition to unsubstituted xylans. Immunocytochemical analyses indicated the presence of both epitopes in secondary cell walls of xylem but differences in occurrence in other cell types.

In vitro allergenicity of peanut after hydrolysis in the presence of polysaccharides.

BACKGROUND: Peanut is a major allergenic product. Manufacturing processes used in food industries to improve the physicochemical properties of food-based peanut (stabilization, texturization), could cause a modification of the digestibility of peanut proteins and, consequently, their allergenicity. OBJECTIVE: This study aimed at examining the influence of polysaccharides, i.e., gum arabic, low methylated pectin (LMP) and xylan, on the in vitro hydrolysis of peanut protein isolate (PPI) and the in vitro allergenicity of the digestion products. METHODS: PPI was hydrolysed during a two-step in vitro hydrolysis by pepsin, followed by a trypsin/chymotrypsin (T/C) mixture performed in dialysis bags with molecular weight cut-offs (MWCO) of 1000 or 8000 Da. SDS-PAGE electrophoresis and immunoblotting were assessed on the peptic and T/C digestion products in (retentates) and out of the dialysis bags (dialysates). RESULTS: Hydrolysis by all of the digestive enzymes showed retention of some proteins in the dialysis bags in the presence of gum arabic and xylan. The retentates were recognized by IgG and IgE, particularly peptides <20 kDa. The IgE binding with peptides of retentate containing xylan from the dialysis bag with an MWCO of 1000 Da was reduced. The immunoreactivity of hydrolysis products in dialysates was considerably reduced by polysaccharides, regardless of the dialysis bag. CONCLUSION: Reduction of PPI hydrolysis was probably due to non-specific interactions between polysaccharides and peptides. In retentates, IgE-binding epitopes were reduced by digestion and the presence of xylan. In dialysates, they were reduced by all of the polysaccharides. This work highlights the possibility of modulating this food allergy through optimized formulation.

Characterization of immunomodulatory polysaccharides from Salvia officinalis L.

Crude polysaccharide fractions, rich mainly in arabinogalactans (A), pectin (B) and glucuronoxylan-related polymers (D), have been obtained from aerial parts of sage (Salvia officinalis L.) by sequential extraction with various reagents. Arabinogalactans displayed on HPLC a dominance of lower molecular-mass polymers (MW < 10,000), while pectin and glucuronoxylan-related polysaccharides showed predominance of polymers with MW > 50,000. Individual polysaccharide fractions were examined for their immunomodulatory activity in the in vitro comitogenic thymocyte test. The polysaccharide fractions tested possessed the capacity to induce rat thymocyte proliferation in the order D>B>A. Besides, fraction D possessed a significant comitogenic effect, and the SIcomit/SImit ratio 3-4 indicates potential adjuvant properties of this glucuronoxylan-rich material.

Highly substituted glucuronoarabinoxylans (hsGAXs) and low-branched xylans show a distinct localization pattern in the tissues of Zea mays L.

Polyclonal antibodies which recognized highly substituted glucuronoarabinoxylans (hsGAXs) and low-branched xylans and did not cross-react with each other, were raised in order to examine localization of these epitopes in internodes of maize. Immunofluorescent labeling revealed different pattern between two succeeding developmental stages. The hsGAX epitope was localized evenly in primary walls in all tissue types, and strongly in unlignified secondary walls in phloem. However, lignified secondary walls in protoxylem, parenchyma and a part of fibers were faintly labeled with this epitope. Moreover, the epitope showed limited binding in lignified parenchyma and fiber walls at ultrastructural level. Low-branched xylan epitope was localized evenly throughout lignified walls in all tissue types. This epitope was also localized only in lignified walls of other organs such as leaf, root apex and dark-grown mesocotyl. Low-branched xylans are significantly related to lignification. Localization of hsGAX epitope in their organs was similar to that in internodes. The hsGAX epitope was distributed both in unlignified walls of all tissues and in lignified walls of parenchyma and annular thickening of protoxylem. We propose that hsGAX has separate functions in lignified and unlignified tissues. In conclusion, at tissue level, hsGAX is localized mainly in unlignified walls, and low-branched xylans in lignified walls.