Elevated levels of serum antibodies to the lectin wheat germ agglutinin in celiac children lend support to the gluten-lectin theory of celiac disease

Reaction of Lectin-Specific Antibody with Human Tissue: Possible Contributions to Autoimmunity

The aim of this study was to examine the direct reaction of specific lectin/agglutinin antibodies to different tissue antigens to confirm the theory that reactivity between them may contribute to autoimmunities. Lectins are carbohydrate-binding proteins found in nearly all fruits and vegetables. Undigested lectins can penetrate the gut barriers, provoking an immune response that results in the production of antibodies against them. Using an enzyme-linked immunosorbent assay, we reacted lectin-specific antibodies with 62 different tissue antigens. Wheat germ agglutinin-specific antibody was the most reactive with the tissue antigens (37 tissues out of 62), followed by red kidney bean phytohemagglutinin-specific antibody (20), soybean agglutinin-specific antibody (20), and peanut agglutinin-specific antibody (15). This reaction between anti-lectin antibodies and many human tissue antigens may be due to possible molecular mimicry and cross-reactivity. After our results confirmed that anti-lectin antibodies bind with human tissues, we wanted to determine the prevalence of these antibodies in the blood of 500 nominally healthy donors. The percentage elevation of antibodies against different lectins ranged from 12 to 16% (Immunoglobulin G), 9.7-14.7% (Immunoglobulin A), 12-18% (Immunoglobulin M), and 7.8-14.6% (Immunoglobulin E). Serial dilutions and inhibition study confirmed that these reactions were specific. Finally, we tested the lectin-specific antibody level in sera both negative and positive for RF and ANA and found that IgM anti-lectin antibody levels were highly correlated with RF but not with ANA level. The reaction of anti-lectin antibodies with human tissue components and their detection in RF-positive samples may describe mechanisms by which the production of antibodies against undigested lectins may contribute to the pathogenesis of some autoimmune diseases.

Interaction between food antigens and the immune system: Association with autoimmune disorders

It has been shown that environmental factors such as infections, chemicals, and diet play a major role in autoimmune diseases; however, relatively little attention has been given to food components as the most prevalent modifiers of these afflictions. This review summarizes the current body of knowledge related to different mechanisms and associations between food proteins/peptides and autoimmune disorders. The primary factor controlling food-related immune reactions is the oral tolerance mechanism. The failure of oral tolerance triggers immune reactivity against dietary antigens, which may initiate or exacerbate autoimmune disease when the food antigen shares homology with human tissue antigens. Because the conformational fit between food antigens and a host's self-determinants has been determined for only a few food proteins, we examined evidence related to the reaction of affinity-purified disease-specific antibody with different food antigens. We also studied the reaction of monoclonal or polyclonal tissue-specific antibodies with various food antigens and the reaction of food-specific antibodies with human tissue antigens. Examining the assembled information, we postulated that chemical modification of food proteins by different toxicants in food may result in immune reaction against modified food proteins that cross-react with tissue antigens, resulting in autoimmune reactivity. Because we are what our microbiome eats, food can change the gut commensals, and toxins can breach the gut barrier, penetrating into different organs where they can initiate autoimmune response. Conversely, there are also foods and supplements that help maintain oral tolerance and microbiome homeostasis. Understanding the potential link between specific food consumption and autoimmunity in humans may lay the foundation for further research about the proper diet in the prevention of autoimmune diseases.

Overlap of Characteristic Serological Antibodies in Rheumatoid Arthritis and Wheat-Related Disorders

Background and Aims

Rheumatoid arthritis (RA) and celiac disease (CD) are members of the autoimmune disease family while they have been shown to share multiple aspects in epidemiology and clinical manifestations. The aim of this study was to assess the presence of wheat protein antibodies in RA seropositive subjects and the presence of RA diagnostic markers in subjects with seropositive wheat-related disorders including CD.

Methods

Serum samples were collected from 844 subjects with joint pain and/or gastrointestinal symptoms and tested by a CD panel (anti-tTG and anti-DGP), a Wheat Zoomer (WZ) antibody panel (IgG/IgA to 14 wheat proteins), and a RA panel (anti-CCP and anti-RF). Retrospective analysis was completed using de-identified clinical data and test results.

Results

The prevalence of RA markers was first investigated in CD- or WZ-positive subjects and negative controls. 49 subjects were seropositive in the CD panel with 10 (20%) RA positivity. 605 subjects were seropositive in the WZ panel with 106 (18%) RA positivity. 222 subjects were seronegative in either panels with 12 (6%) RA positivity. Next, the frequency of the CD markers and the clinically relevant wheat protein antibodies were investigated in the RA-positive subjects and negative controls. 128 subjects in this cohort were seropositive in the RA panel with 10 (8%) CD positivity and 106 (83%) WZ positivity, compared to 716 RA seronegative controls with 39 (5%) CD positivity and 499 (70%) WZ positivity.

Conclusions

Our data presents an apparent trend of overlapped serological antibody biomarker positivity in RA and wheat-related disorders.

High Frequency of Extractable Nuclear Autoantibodies in Wheat-Related Disorders

Background and aims:

There has been broad interest to explore the presence of autoimmunity among wheat-sensitive individuals, but neither the pathogenesis nor the relevance has been established. In this study, we evaluated the frequencies and levels of autoantibodies, which are important biomarkers of autoimmunity, in subjects with wheat-related disorders and controls. Anti-nuclear antibodies (ANA) and the specific ones against extractable nuclear antigens (ENA) were investigated.

Methods:

A total of 713 subjects who showed symptoms related to wheat ingestion were addressed to Vibrant America Clinical Laboratory from December 2015 to November 2017. Serum samples were collected from all subjects and tested with a wheat protein antibody panel (IgG and IgA to 18 proteins at the peptide level) and an autoantibody panel (ANA by immunofluorescence analysis and 10 ENA antibodies). Retrospective analysis was completed using de-identified clinical data and test results.

Results:

In the retrospective analysis, 38 (5%) were seropositive in a Celiac Disease panel, 491 (83%) were seropositive in a wheat protein antibody panel “Wheat Zoomer,” and 84 (12%) were seronegative in both panels. Anti-nuclear antibodies were detected in similar portions of the celiac disease subjects (13%), the Wheat Zoomer–positive subjects (12%), and seronegative controls (15%), which is also very close to the reported occurrence of ANA positivity (15%) in the healthy population. The prevalence of anti-ENA was reported to be less than 2% in the general population; however, our study found it to be much higher in the celiac disease subjects (29%) and the wheat-sensitive subjects (27%), compared with a smaller proportion of seronegative controls (19%). The prevalence of anti-histone was especially prominent among the celiac disease subjects (73%) and the Wheat Zoomer–positive subjects (60%).

Conclusions:

High proportions of wheat-related disease subjects carry ENA antibodies that are important specific biomarkers of autoimmunity.

Plant Lectins Activate the NLRP3 Inflammasome To Promote Inflammatory Disorders

Plant-derived dietary lectins have been reported to be involved in the pathogenesis of several inflammatory diseases, including inflammatory bowel disease, diabetes, rheumatoid arthritis, and celiac disease, but little is known about the molecular mechanisms underlying lectin-induced inflammation. In this study, we showed that plant lectins can induce caspase-1 activation and IL-1β secretion via the NLRP3 inflammasome. Lectins were internalized and subsequently escaped from the lysosome and then translocated to the endoplasmic reticulum. Endoplasmic reticulum-loaded plant lectins then triggered Ca²⁺ release and mitochondrial damage, and inhibition of Ca²⁺ release and mitochondrial reactive oxygen species by chemical inhibitors significantly suppressed NLRP3 inflammasome activation. In vivo, plant lectin-induced inflammation and tissue damage also depended on the NLRP3 inflammasome. Our findings indicate that plant lectins can act as an exogenous "danger signal" that can activate the NLRP3 inflammasome and suggest that dietary lectins might promote inflammatory diseases via the NLRP3 inflammasome.

The lectin-cell interaction and its implications to intestinal lectin-mediated drug delivery

Based on the fact that oligosaccharides encode biological information, the biorecognition between lectinised drug delivery systems and glycosylated structures in the intestine can be exploited for improved peroral therapy. Basic research revealed that some lectins can mediate mucoadhesion, cytoadhesion, and cytoinvasion of drugs. Entering the vesicular pathway by receptor mediated endocytosis, part of the conjugated drug is accumulated within the lysosomes. Additionally, part of the drug is supposed to be transported across the epithelium. Moreover, factors probably adversely influencing feasibility of the concept such as toxicity, immunogenicity, and intestinal stability of plant lectins are discussed. As exemplified by lectin-grafted prodrug and carrier systems, this strategy is expected to improve absorption and probably bioavailability of poorly absorbable drugs, peptides and proteins as well as therapeutic DNA.

Update on immunologic basis of celiac disease

During the past few years several seminal studies have greatly expanded our knowledge on celiac disease pathogenesis. This review focuses on aspects that have been most properly addressed and where substantial new information has been gathered include. Topics covered include (a) the identification of T-cell epitopes in gluten and the mechanisms of specific T-cell response in celiac disease small intestine; (b) the mechanisms of induction of mucosal lesion; and (c) the putative role of non-T-cell factors in driving mucosal response to gliadin. After discussing a brief history of the "quest for the cause of celiac disease," we examine the development of the typical celiac lesion (the crypt hyperplastic mucosal atrophy) as it generally unfolds: the increased entry of dietary antigens; the early changes, linked to specific components of the innate immunity rather than to its adaptive branch; the most thoroughly investigated subsequent response, involving a strong T-cell response and cytokines; and the factors responsible for enterocytes' death. The emerging pattern is that of a complex interaction of factors, although far from being completely understood, but fascinating as it opens an incredible window of knowledge on an autoimmune disorder whose environmental factor is known, whose autoantigen is known, whose autoantibodies are known: a truly unique situation in medicine.

Detection of specific IgE to human milk proteins in sera of atopic infants

Specific IgE (sIgE) for cow's milk proteins (CMP) have been reported to be present in blood sera of exclusively breast-fed infants. The aim of this study was to find whether the presence of sIgE to human milk proteins in the sera of exclusively breast-fed infants could explain the apparent detection of sIgE to CMP in infants that were never previously in contact with cow's milk. sIgE for human milk whey proteins were found in the blood sera of atopic infants, and these sIgE strongly cross-reacted with the corresponding CMP. In none of the sera examined were sIgE to bovine beta-lactoglobulin detected.

Hydrophobic interactions between gliadin and proteins and celiac disease

Gliadin-protein interaction and its relationship to the pathogenesis hypotheses of celiac disease was investigated. Wheat germ agglutinin was not immunodetected in gliadin preparations. Peptic-tryptic gliadin digest was used to study the gliadin-protein interactions by crossed immunoelectrophoresis and affinity blotting. Biotinylated gliadin digest interacted with IgG and bovine serum albumin but not with several glycoproteins. Since albumin and IgG light chains are not glycosylated, this interaction is not lectin-like, neither completely immunological because of recognition of the IgG Fc fraction. Immobilized and boiled IgG was not recognized by gliadin digest as a lectin. Gliadin digest fractions from T-gel chromatography reduced the fluorescence intensity of cis-parinaric acid bound to albumin. The gliadin-protein interaction is not lectin-like or completely immunological but hydrophobic. Hydrophobicity of gliadins may contribute to the pathogenic events that result in celiac disease.