Effect of horse gram lectin (Dolichos biflorus agglutinin) on degranulation of mast cells and basophils of atopic subjects: identification as an allergen

Legume Allergens Pea, Chickpea, Lentil, Lupine and Beyond

PURPOSE OF THE REVIEW

In the last decade, an increasing trend towards a supposedly healthier vegan diet could be observed. However, recently, more cases of allergic reactions to plants and plant-based products such as meat-substitution products, which are often prepared with legumes, were reported. Here, we provide the current knowledge on legume allergen sources and the respective single allergens. We answer the question of which legumes beside the well-known food allergen sources peanut and soybean should be considered for diagnostic and therapeutic measures.

RECENT FINDINGS

These "non-priority" legumes, including beans, pea, lentils, chickpea, lupine, cowpea, pigeon pea, and fenugreek, are potentially new important allergen sources, causing mild-to-severe allergic reactions. Severe reactions have been described particularly for peas and lupine. An interesting aspect is the connection between anaphylactic reactions and exercise (food-dependent exercise-induced anaphylaxis), which has only recently been highlighted for legumes such as soybean, lentils and chickpea. Most allergic reactions derive from IgE cross-reactions to homologous proteins, for example between peanut and lupine, which is of particular importance for peanut-allergic individuals ignorant to these cross-reactions. From our findings we conclude that there is a need for large-scale studies that are geographically distinctive because most studies are case reports, and geographic differences of allergic diseases towards these legumes have already been discovered for well-known "Big 9" allergen sources such as peanut and soybean. Furthermore, the review illustrates the need for a better molecular diagnostic for these emerging non-priority allergen sources to evaluate IgE cross-reactivities to known allergens and identify true allergic reactions.

Recognition factors of Dolichos biflorus agglutinin (DBA) and their accommodation sites

Dolichos biflorus agglutinin (DBA) is one of the well known plant lectins that are widely used in clinical serology to differentiate human blood group A1 and A2 erythrocytes and also applied to glycobiology. However, the knowledge of recognition factors of polyvalent (super) glycotopes in glycans and the roles of functional group and epimer in monosaccharide (sub-monosaccharide recognition factor) have not been well established. The size and shape of the recognition (combining) site of DBA has not been clearly defined. In this study, many importnat recognition factors of DBA-glycan binding were characterized by our established enzyme-linked lectinosorbent (ELLSA) and inhibition assays. The results of these assays showed that the intensity profile of the recognition factors for the major combining site of DBA was expressed by Mass relative potency (Mass R.P.) and shown by decreasing order of high density of polyvalent GalNAcα1 → (super glycotopes, 3.7 × 103) >> the corresponding β anomers >> monomeric GalNAcα1 → related glycotopes (GalNAc as 1.0) >> their GalNAc β-anomers >> Gal (absence of NHCH3CO at carbon-2 of GAlNAc) and GlcNAc (different epimer of Carbon-4 in GalNAc). From the all data available, it is proposed that the combining site of DBA should consist of a small cavity shape as major site and most complementary to monomeric GalNAcα → located at both terminal reducing end (Tn) and nonreducing end of glycan chains, and with a wide and broad area as subsite to accomodate from mono- to tetra-saccharides (GalNAcβ, Galβ1 → 3/4GlcNAc, lFuc1 → 2Galβ1 → 3/4GlcNAc, GalNAcβ1 → 3Galα1 → 4Galβ1 → 4Glc) at the nonreducing side. In this study, it has provided the most (comprehensive) recognition knowledge of DBA-glycan interactions at the factors of glycotope, super glycotope/sub-monosaccharide levels. Thus, it should expand and upgrade the conventional concept of the combining (recognition) site of DBA since 1980s.

Are Dietary Lectins Relevant Allergens in Plant Food Allergy?

Lectins or carbohydrate-binding proteins are widely distributed in seeds and vegetative parts of edible plant species. A few lectins from different fruits and vegetables have been identified as potential food allergens, including wheat agglutinin, hevein (Hev b 6.02) from the rubber tree and chitinases containing a hevein domain from different fruits and vegetables. However, other well-known lectins from legumes have been demonstrated to behave as potential food allergens taking into account their ability to specifically bind IgE from allergic patients, trigger the degranulation of sensitized basophils, and to elicit interleukin secretion in sensitized people. These allergens include members from the different families of higher plant lectins, including legume lectins, type II ribosome-inactivating proteins (RIP-II), wheat germ agglutinin (WGA), jacalin-related lectins, GNA (Galanthus nivalis agglutinin)-like lectins, and Nictaba-related lectins. Most of these potentially active lectin allergens belong to the group of seed storage proteins (legume lectins), pathogenesis-related protein family PR-3 comprising hevein and class I, II, IV, V, VI, and VII chitinases containing a hevein domain, and type II ribosome-inactivating proteins containing a ricin B-chain domain (RIP-II). In the present review, we present an exhaustive survey of both the structural organization and structural features responsible for the allergenic potency of lectins, with special reference to lectins from dietary plant species/tissues consumed in Western countries.

The lectin ArtinM induces recruitment of rat mast cells from the bone marrow to the peritoneal cavity

Background

The D-mannose binding lectin ArtinM is known to recruit neutrophils, to degranulate mast cells and may have potential therapeutic applications. However, the effect of ArtinM on mast cell recruitment has not been investigated.

Methodology

Male Wistar rats were injected i.p. with ArtinM or ConA (control). The ability of the lectin to degranulate peritoneal and mesenteric mast cells was examined. Recruitment of mast cells to the peritoneal cavity and mesentery after ArtinM injection was examined with or without depletion of peritoneal mast cells by distilled water.

Results

ArtinM degranulated both peritoneal and mesentery mast cells in vitro. Three days after i.p. injection of the lectin there were reduced numbers of mast cells in the peritoneal lavage, while at 7 days post injection of ArtinM, the number of peritoneal mast cells was close to control values. Since immature mast cells are recruited from the bone marrow, the effect of the lectin on bone marrow mast cells was examined. Injection of ArtinM resulted in an increased number of mast cells in the bone marrow. To determine if degranulation of mast cells in the peritoneal cavity was required for the increase in bone marrow mast cells, the peritoneal cavity was depleted of mast cells with ultrapure water. Exposure to ArtinM increased the number of mast cells in the bone marrow of rats depleted of peritoneal mast cells.

Conclusions

The ArtinM induced recruitment of mast cells from the bone marrow to the peritoneal cavity may partially explain the therapeutic actions of ArtinM.

Identity of the immunomodulatory proteins from garlic (Allium sativum) with the major garlic lectins or agglutinins

Garlic (Allium sativum), an important medicinal spice, displays a plethora of biological effects including immunomodulation. Although some immunomodulatory proteins from garlic have been described, their identities are still unknown. The present study was envisaged to isolate immunomodulatory proteins from raw garlic, and examine their effects on certain cells of the immune system (lymphocytes, mast cells, and basophils) in relation to mitogenicity and hypersensitivity. Three protein components of approximately 13 kD (QR-1, QR-2, and QR-3 in the ratio 7:28:1) were separated by Q-Sepharose chromatography of 30 kD ultrafiltrate of raw garlic extract. All the 3 proteins exhibited mitogenic activity towards human peripheral blood lymphocytes, murine splenocytes and thymocytes. The mitogenicity of QR-2 was the highest among the three immunomodulatory proteins. QR-1 and QR-2 displayed hemagglutination and mannose-binding activities; QR-3 showed only mannose-binding activity. Immunoreactivity of rabbit anti-QR-1 and anti-QR-2 polyclonal antisera showed specificity for their respective antigens as well as mutual cross-reactivity; QR-3 was better recognized by anti-QR-2 (82%) than by anti-QR-1 (55%). QR-2 induced a 2-fold higher histamine release in vitro from leukocytes of atopic subjects compared to that of non-atopic subjects. In all functional studies, QR-2 was more potent compared to QR-1. Taken together, all these results indicate that the two major proteins QR-2 and QR-1 present in a ratio of 4:1 in raw garlic contribute to garlic's immunomodulatory activity, and their characteristics are markedly similar to the abundant Allium sativum agglutinins (ASA) I and II, respectively.

Wheat germ agglutinin-modified trifunctional nanospheres for cell recognition

A simple and convenient strategy has been put forward to fabricate smart fluorescent magnetic wheat germ agglutinin-modified trifunctional nanospheres (WGA-TFNS) for recognition of human prostate carcinoma DU-145 cells which are surface-expressed with sialic acid and N-acetylglucosamine. These TFNS can be easily manipulated, tracked, and conveniently used to capture and separate target cells. The presence of wheat germ agglutinin on the surface of WGA-TFNS was confirmed by FTIR, biorecognition of carboxymethyl chitin-modified quantum dots (CM-CT-QDs), and bacterium Staphylococcus aureus. The success in recognizing DU-145 cells by the WGA-TFNS indicates that WGA-TFNS could be applicable.

Potato lectin activates basophils and mast cells of atopic subjects by its interaction with core chitobiose of cell-bound non-specific immunoglobulin E

A major factor in non-allergic food hypersensitivity could be the interaction of dietary lectins with mast cells and basophils. Because immunoglobulin E (IgE) contains 10-12% carbohydrates, lectins can activate and degranulate these cells by cross-linking the glycans of cell-bound IgE. The present objective focuses on the effect of potato lectin (Solanum tuberosum agglutinin; STA) for its ability to release histamine from basophils in vitro and mast cells in vivo from non-atopic and atopic subjects. In this study, subjects were selected randomly based on case history and skin prick test responses with food, pollen and house dust mite extracts. Skin prick test (SPT) was performed with STA at 100 microg/ml concentration. Histamine release was performed using leucocytes from non-atopic and atopic subjects and rat peritoneal exudate cells. SPT on 110 atopic subjects using STA showed 39 subjects positive (35%); however, none showed STA-specific IgE; among 20 non-atopic subjects, none were positive by SPT. Maximal histamine release was found to be 65% in atopic subjects (n = 7) compared to 28% in non-atopic subjects (n = 5); the release was inhibited specifically by oligomers of N-acetylglucosamine and correlates well with serum total IgE levels (R(2) = 0.923). Binding of STA to N-linked glycoproteins (horseradish peroxidase, avidin and IgG) was positive by dot blot and binding assay. As potato lectin activates and degranulates both mast cells and basophils by interacting with the chitobiose core of IgE glycans, higher intake of potato may increase the clinical symptoms as a result of non-allergic food hypersensitivity in atopic subjects.