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AOP: 524
Title
Gluten intake and recognition leading to celiac disease
Short name
Graphical Representation
Point of Contact
Contributors
- Pablo Rodriguez Fernandez
- Estefanía Noriega Fernández
- Aina Gil González
- Antonio Fernandez Dumont
Coaches
- Shihori Tanabe
OECD Information Table
OECD Project # | OECD Status | Reviewer's Reports | Journal-format Article | OECD iLibrary Published Version |
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This AOP was last modified on February 04, 2025 15:15
Revision dates for related pages
Page | Revision Date/Time |
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Human leukocyte antigen DQ2/8-gluten complexes, formation | January 05, 2025 15:24 |
Gluten-reactive T cell receptors, generation | January 05, 2025 16:53 |
Gluten-reactive and transglutaminase 2 reactive B cell receptors, generation | December 03, 2024 06:33 |
Innate immune response, activation | December 04, 2024 12:53 |
Gluten-reactive B cells and transglutaminase 2-reactive B cells, activation | January 04, 2025 09:14 |
Intestinal barrier, disruption | June 21, 2022 11:19 |
Celiac disease | December 02, 2024 14:41 |
Gluten-reactive CD4+ T cells, activation | January 04, 2025 09:14 |
Gluten reactive adaptive T-cells with antigen presenting cells, co-localization | December 20, 2024 08:41 |
Formation of HLA-DQ2/8-gluten complexes leads to Co-localization of gluten reactive adaptive T-cells with APC | January 05, 2025 17:49 |
Generation of gluten-reactive and TG2-reactive B cell receptors leads to Co-localization of gluten reactive adaptive T-cells with APC | January 05, 2025 18:13 |
Generation of gluten-reactive T cell receptors leads to Co-localization of gluten reactive adaptive T-cells with APC | January 25, 2025 06:04 |
Co-localization of gluten reactive adaptive T-cells with APC leads to Activation of the innate immune response | January 23, 2025 12:30 |
Activation of the innate immune response leads to Activation of gluten-reactive CD4+ T cells | January 23, 2025 12:35 |
Activation of gluten-reactive CD4+ T cells leads to Activation of gluten- and TG2-reactive B cells | January 11, 2025 13:47 |
Activation of gluten- and TG2-reactive B cells leads to Disruption of the intestinal barrier | January 04, 2025 10:03 |
Disruption of the intestinal barrier leads to Celiac disease | January 08, 2025 15:47 |
Abstract
Celiac disease is an immune-mediated disorder triggered by the ingestion of gluten in genetically susceptible individuals carrying human leukocyte antigen (HLA)-DQ2 or HLA-DQ8 molecules. This Adverse Outcome Pathway (AOP) describes the sequence of molecular and cellular events leading to celiac disease, beginning with key molecular initiating events (MIEs) and culminating in intestinal damage and disease manifestation.
The pathway is initiated by the formation of HLA-DQ2/8-gluten complexes, the generation of gluten-reactive T cell receptors, and the production of gluten- and transglutaminase 2 (TG2)-reactive B cell receptors. These MIEs facilitate the co-localization of gluten-reactive adaptive T-cells with antigen-presenting cells (APCs), an essential step in the immune response. This interaction triggers the activation of the innate immune response and subsequently leads to the activation of gluten-reactive CD4+ T cells. The cascade continues with the activation of gluten- and TG2-reactive B cells, which further amplifies the immune response and contributes to the disruption of the intestinal barrier. The final adverse outcome (AO) is the development of celiac disease, characterized by chronic intestinal inflammation, villous atrophy, and malabsorption.
The relationships between key events (KEs) in this AOP are supported by moderate levels of evidence, reflecting a well-characterized yet complex immunopathological process. Understanding this AOP provides valuable insights for risk assessment, the development of targeted therapies, and the refinement of strategies for gluten-related disorder management.
AOP Development Strategy
Context
In 2017, the EFSA GMO Panel published a guidance document (EFSA, 2017) that, for the first time, outlined a specific risk assessment strategy to predict the capacity of innovative or novel proteins to trigger celiac disease. This strategy, characterized by an integrated, stepwise, case-by-case approach, was made possible due to the well-documented pathogenesis of celiac disease and the known proteins involved. Specifically, gluten peptides presented by the disease-predisposing Human Leukocyte Antigen (HLA) class II molecules, HLA-DQ2 or HLA-DQ8, activate pro-inflammatory T-cells in the inflamed intestines of patients.
Ongoing efforts to refine risk assessment methodologies in this area are driven by new findings that suggest proteins from sources other than cereals may pose a hazard to individuals with celiac disease (Peterson et al., 2019) . This AOP is created to integrate the scientific knowledge into a conceptual framework in the regulatory context.
The risk assessment strategy developed for evaluating the potential of innovative or novel proteins to induce celiac disease is regarded as a benchmark, serving as an inspiration for the broader food safety assessment of novel proteins in the food sector.
Strategy
EFSA launched a procurement as a preparatory work for the development of adverse outcome pathways relevant for the capacity of proteins to trigger celiac disease [3] . Specifically, a search strategy was developed and eligibility (inclusion/exclusion) criteria were defined for the screening and retrieval of relevant evidence on molecular signals of proteins to trigger celiac disease published in the scientific literature. Abstract/title screening and full-text screening were systematically framed, extracting data from the selected full text articles, and assessing the risk of bias of each publication (Bebi et al., 2023).
The aim was to develop evidence-based AOPs that outline molecular signals of proteins capable of triggering celiac disease, serving as a foundation for further AOP development. While the approach relied on systematic information retrieval, relevance screening, and critical appraisal of the data, it was only a starting point. Expert knowledge was then integrated to complement this information, highlighting key publications and providing a rationale for the finalized AOP framework. This project was also included in the OECD AOP development work plan by the Extended Advisory Group on Molecular Screening and Toxicogenomic (EAGMST) guarantying coaching support and an additional layer of internal review.
Summary of the AOP
Events:
Molecular Initiating Events (MIE)
Key Events (KE)
Adverse Outcomes (AO)
Type | Event ID | Title | Short name |
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MIE | 2252 | Human leukocyte antigen DQ2/8-gluten complexes, formation | Formation of HLA-DQ2/8-gluten complexes |
MIE | 2253 | Gluten-reactive T cell receptors, generation | Generation of gluten-reactive T cell receptors |
MIE | 2254 | Gluten-reactive and transglutaminase 2 reactive B cell receptors, generation | Generation of gluten-reactive and TG2-reactive B cell receptors |
KE | 2275 | Gluten reactive adaptive T-cells with antigen presenting cells, co-localization | Co-localization of gluten reactive adaptive T-cells with APC |
KE | 2255 | Innate immune response, activation | Activation of the innate immune response |
KE | 2260 | Gluten-reactive CD4+ T cells, activation | Activation of gluten-reactive CD4+ T cells |
KE | 2256 | Gluten-reactive B cells and transglutaminase 2-reactive B cells, activation | Activation of gluten- and TG2-reactive B cells |
KE | 1931 | Intestinal barrier, disruption | Disruption of the intestinal barrier |
AO | 2257 | Celiac disease | Celiac disease |
Relationships Between Two Key Events (Including MIEs and AOs)
Title | Adjacency | Evidence | Quantitative Understanding |
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Network View
Prototypical Stressors
Life Stage Applicability
Life stage | Evidence |
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All life stages | High |
Taxonomic Applicability
Term | Scientific Term | Evidence | Link |
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human | Homo sapiens | High | NCBI |
Sex Applicability
Sex | Evidence |
---|---|
Unspecific | High |
Overall Assessment of the AOP
KER1: Formation of HLA-DQ2/8-gluten complexes leads to Co-localization of gluten-reactive adaptive T-cells with APC
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: The formation of the HLA-DQ2/8-gluten complex is a fundamental event for initiating the immune response in genetically predisposed individuals. The co-localization of gluten-reactive adaptive T cells with antigen-presenting cells (APCs) depends on the recognition of these complexes by the immune system. This relationship is essential for activating the adaptive immune system, a critical step in the development of celiac disease. Supporting Evidence: The interaction between gluten-HLA complexes and T cells is well-documented, and co-localization with APCs is required for T-cell activation (Sollid, 2002; van de Wal et al., 1999).
KER2: Generation of gluten-reactive and TG2-reactive B cell receptors leads to Co-localization of gluten-reactive adaptive T-cells with APC
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: The generation of gluten-reactive and TG2-reactive B cell receptors facilitates the production of antibodies that contribute to the autoimmune response in celiac disease. While the direct influence on T-cell co-localization is less clear, the B-cell receptor generation is part of the broader immune response, influencing the progression of celiac disease. The co-localization of T-cells with APCs is indirectly impacted by the production of antibodies and antigen presentation. Supporting Evidence: While there is strong evidence for the generation of gluten-reactive B cells, the direct relationship with T-cell co-localization has moderate support, but it is still considered relevant for the disease process (Kagnoff, 2007).
KER3: Generation of gluten-reactive T cell receptors leads to Co-localization of gluten-reactive adaptive T-cells with APC
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: Gluten-reactive TCR generation is a critical early event in the immune response to gluten. Once these TCRs are generated, the T-cells are able to recognize gluten peptides presented by APCs, facilitating their co-localization. This step is essential for initiating the adaptive immune response, a key event in the pathogenesis of celiac disease. Supporting Evidence: There is strong evidence for the role of gluten-reactive TCRs in initiating immune responses, and their interaction with APCs is fundamental for the disease process (Jabri & Sollid, 2017).
KER4: Co-localization of gluten-reactive adaptive T-cells with APC leads to Activation of the innate immune response
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: The co-localization of gluten-reactive T-cells with APCs activates the adaptive immune system, which in turn triggers innate immune pathways. Activation of the innate immune response amplifies the overall immune reaction, driving inflammation and tissue damage seen in celiac disease. Without this co-localization, the full immune activation needed for disease progression would not occur. Supporting Evidence: Studies indicate that activation of adaptive T-cells by APCs is tightly linked to subsequent activation of innate immune pathways (Lundin et al., 1993; Anderson et al., 2011).
KER5: Activation of the innate immune response leads to Activation of gluten-reactive CD4+ T cells
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: The innate immune response plays a pivotal role in amplifying the activation of gluten-reactive CD4+ T cells, which is essential for driving the adaptive immune response in celiac disease. This relationship is critical because it ensures that the immune system's inflammatory reaction is properly mediated and directed toward the intestines. Supporting Evidence: The innate immune system is known to activate CD4+ T cells in response to antigenic stimulation, further promoting the inflammatory cascade in celiac disease.
KER6: Activation of gluten-reactive CD4+ T cells leads to Activation of gluten- and TG2-reactive B cells
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: The activation of gluten-reactive CD4+ T cells is necessary to help activate B cells that produce gluten- and TG2-specific antibodies. These antibodies are markers of disease and contribute to the autoimmune responses that drive the pathology of celiac disease. Without T-cell activation, B-cell activation cannot occur, and the autoimmune response would be incomplete. Supporting Evidence: The interaction between activated T cells and B cells is well-established in the context of autoimmune diseases like celiac disease, where T-helper cells provide necessary signals for B cell activation (Kagnoff, 2007).
KER7: Activation of gluten- and TG2-reactive B cells leads to Disruption of the intestinal barrier
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: The activation of gluten- and TG2-reactive B cells results in the production of antibodies, such as anti-TG2, which play a significant role in tissue damage. This damage contributes to the disruption of the intestinal barrier, a hallmark of celiac disease. Without B-cell activation, the autoimmune-mediated intestinal damage would be less pronounced, and the disease would not progress in the same way. Supporting Evidence: The presence of anti-TG2 antibodies and their involvement in intestinal injury is well-documented in celiac disease (Lundin et al., 1993; Green & Cellier, 2007).
KER8: Disruption of the intestinal barrier leads to Celiac Disease
- Adjacency: Adjacent
- Evidence: Moderate
- Essentiality: High Rationale: The disruption of the intestinal barrier is the key event that allows gluten peptides and other immune activators to enter the mucosa, triggering the immune response and leading to celiac disease. This barrier disruption is essential for disease progression, as it creates the conditions for subsequent inflammation, villous atrophy, and clinical symptoms. Supporting Evidence: The breakdown of the intestinal barrier is considered a critical step in the pathogenesis of celiac disease. Without this disruption, immune activation would be limited, and disease symptoms would not manifest (Anderson et al., 2011).
Domain of Applicability
The AOP applies specifically to humans, as celiac disease is inherently linked to the HLA-DQ2/8 genotype, which is unique to humans. The described mechanisms are particularly relevant to individuals with genetic susceptibility.
Essentiality of the Key Events
MIE1: Formation of HLA-DQ2/8-gluten Complexes
Essentiality: High Rationale: The presence of HLA-DQ2/8 is a critical requirement for the development of celiac disease. Without these alleles, individuals cannot form gluten-HLA complexes, and celiac disease does not occur. The formation of this complex is a fundamental step in initiating the immune response against gluten in genetically predisposed individuals. (Sollid, 2002; van de Wal et al., 1999)
MIE2: Generation of Gluten-Reactive T Cell Receptors
Essentiality: High Rationale: The generation of gluten-reactive TCRs is essential for the immune system to recognize gluten peptides. This step triggers the adaptive immune response, and individuals who lack gluten-reactive TCRs are unable to develop the disease. Clinical data consistently shows the presence of these TCRs in celiac patients, which play a direct role in the disease process (Lundin et al., 1993; Dieterich et al., 1997).
MIE3: Generation of Gluten-Reactive and TG2-Reactive B Cell Receptors
Essentiality: High Rationale: B cells with receptors for both gluten and transglutaminase 2 (TG2) play a role in the immune response of celiac disease. These B cells contribute to the production of antibodies such as anti-TG2, which are a hallmark of celiac disease. The formation of these receptors is crucial for the onset of the disease as they facilitate the autoimmune response (Kagnoff, 2007).
KE1: Co-localization of Gluten Reactive Adaptive T-cells with APCs
Essentiality: High Rationale: Co-localization of gluten-reactive T cells with antigen-presenting cells (APCs) is essential for the activation of T cells and the subsequent immune response. This interaction is necessary for the initiation of the adaptive immune response, which drives the inflammatory processes seen in celiac disease. Without this step, the disease cannot progress.
KE2: Activation of the Innate Immune Response
Essentiality: High Rationale: Activation of the innate immune response is crucial for amplifying the immune response in celiac disease. This step helps recruit additional immune cells to the site of inflammation and promotes further activation of adaptive immune cells. Disruption of this pathway can prevent the development of disease (Lundin et al., 1993).
KE3: Activation of Gluten-Reactive CD4+ T Cells
Essentiality: High Rationale: The activation of gluten-reactive CD4+ T cells is central to celiac disease pathology. These T cells recognize gluten peptides and drive the autoimmune response, leading to intestinal inflammation and damage. This step is directly linked to the development of disease symptoms and is essential for disease progression (Lundin et al., 1993).
KE4: Activation of Gluten- and TG2-Reactive B Cells
Essentiality: High Rationale: The activation of gluten- and TG2-reactive B cells leads to the production of antibodies such as anti-TG2 and anti-gluten antibodies. These antibodies contribute to the pathological immune response in celiac disease and are markers of disease activity (Kagnoff, 2007).
KE5: Disruption of the Intestinal Barrier
Essentiality: High Rationale: The disruption of the intestinal barrier is a key event in celiac disease and contributes to the leakage of antigens, including gluten peptides, into the intestinal mucosa. This leads to further activation of immune cells and is a critical step in disease pathogenesis. Without this disruption, the immune response would not be sufficiently activated to trigger celiac disease (Anderson et al., 2011).
AO: Celiac Disease
Essentiality: High Rationale: Celiac disease is the adverse outcome of the AOP. It is characterized by chronic inflammation of the small intestine, leading to villous atrophy, malabsorption, and various systemic manifestations. Without the preceding key events, the disease cannot occur. Therefore, celiac disease as an outcome is directly dependent on the successful progression of the earlier KEs (Green & Cellier, 2007).
Evidence Assessment
Known Modulating Factors
Modulating Factor (MF) | Influence or Outcome | KER(s) involved |
---|---|---|
Quantitative Understanding
Considerations for Potential Applications of the AOP (optional)
This AOP holds significant translational value, particularly for:
- Diagnostic development: Insights into antigen presentation and immune responses support biomarker identification (e.g., TG2 autoantibodies).
- Therapeutic strategies: Potential interventions targeting gluten processing, HLA binding, or immune modulation.
- Regulatory applications: Could support safety assessments of gluten-derived products or alternative treatments.
References
- Anderson, R. P., Degano, P., Godkin, A. J., Jewell, D. P., & Hill, A. V. S. (2011). In vivo antigen challenge in celiac disease: A randomized controlled study comparing oat and wheat challenge. Gut, 60(3), 420–427. https://doi.org/10.1136/gut.2010.221762
- Bebi C, Urbani D, Evangelisti M, Grossi V, Russo F, Del Rio A. (2024). Outsourcing preparatory work based on a systematic literature review for the development of adverse outcome pathways (AOPs) relevant for the capacity of proteins to trigger celiac disease. EFSA Supporting publication 2024:EN-8570. doi: 10.2903/sp.efsa.2024.EN-8570.
- Dieterich W, Ehnis T, Bauer M, Donner P, Volta U, Riecken EO, Schuppan D. (1997). Identification of tissue transglutaminase as the autoantigen of celiac disease. Nat Med. 3:797-801.
- EFSA Panel on Genetically Modified Organisms (GMO), Naegeli H, Birch AN, Casacuberta J, De Schrijver A, Gralak MA, Guerche P, et al. (2017). Guidance on allergenicity assessment of genetically modified plants. EFSA Journal, 15(6):4862. doi: 10.2903/j.efsa.2017.4862.
- Green, P. H. R., & Cellier, C. (2007). Celiac disease. New England Journal of Medicine, 357(17), 1731–1743. https://doi.org/10.1056/NEJMra071600
- https://doi.org/10.3109/08916934.2012.665520
- Jabri B, Sollid LM. T Cells in Celiac Disease. J Immunol. 2017 Apr 15;198(8):3005-3014. doi: 10.4049/jimmunol.1601693. PMID: 28373482; PMCID: PMC5426360.
- Kagnoff, M. F. (2007). Celiac disease: Pathogenesis of a model immunogenetic disease. Journal of Clinical Investigation, 117(1), 41–49. https://doi.org/10.1172/JCI30253
- Lundin, K. E. A., Scott, H., Hansen, T., Paulsen, G., Halstensen, T. S., Fausa, O., ... & Sollid, L. M. (1993). Gliadin-specific, HLA-DQ2-restricted T cells isolated from the small intestinal mucosa of celiac disease patients. Journal of Experimental Medicine, 178(1), 187–196. https://doi.org/10.1084/jem.178.1.18
- Petersen J, Ciacchi L, Tran MT, Loh KL, Kooy-Winkelaar Y, Croft NP, Hardy MY, Chen Z, McCluskey J, Anderson RP, Purcell AW, Tye-Din JA, Koning F, Reid HH, Rossjohn J. (2020). T cell receptor cross-reactivity between gliadin and bacterial peptides in celiac disease. Nature Structural & Molecular Biology, 27: 49–61. doi: 10.1038/s41594-019-0354-z
- Sollid, L. M. (2002). Coeliac disease: Dissecting a complex inflammatory disorder. Nature Reviews Immunology, 2(9), 647–655. https://doi.org/10.1038/nri885
- van de Wal, Y., Kooy, Y. M., van Veelen, P. A., Peña, S. A., Mearin, M. L., Molberg, Ø., ... & Koning, F. (1999). Small intestinal T cells of celiac disease patients recognize a natural pepsin fragment of gliadin. Proceedings of the National Academy of Sciences, 96(11), 12005–12010. https://doi.org/10.1073/pnas.96.22.12005