dr. A.R. (Arno) Bourgonje

Education

2018 - 2022 MD/PhD trajectory (cum laude)
Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen

PhD thesis: "Biomarker signatures in pathophysiology and therapeutic interventions in inflammatory bowel diseases: a multimodal approach", 2023 (cum laude).

Promotors: prof. dr. G. Dijkstra, prof. dr. K.N. Faber, prof. dr. H. van Goor & prof. dr. R.K. Weersma.

2020 MSc Medicine  (summa cum laude)
University Medical Center Groningen, University of Groningen

2016 Honours College  (cum laude)
University of Groningen

2016 BSc Medicine  (summa cum laude)
University Medical Center Groningen, University of Groningen

2013 Gymnasium/VWO  (magna cum laude)
Stedelijk Gymnasium Leeuwarden

Professional experience

2023 - 2025 Postdoctoral researcher / physician-scientist
Division of Gastroenterology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, United States

2022 - 2023 Postdoctoral researcher / physician-scientist
Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen

2021 - 2022 Physician-not-in-training ("ANIOS")
Municipal Health Services Groningen (GGD), Groningen, the Netherlands

2019 - 2021 Project assistant
Development of exams and tests for the longitudinal examination program of the Medicine master G2020 curriculum and national Progress Test of Medicine (iVTG), University of Groningen

Research

Inflammatory bowel disease (IBD) is a term mainly used to describe two diseases: Crohn’s disease (CD) and ulcerative colitis (UC). These are complex immune-mediated diseases of the gastrointestinal tract, characterised by a relapse-remitting disease course. Hence, IBD is difficult to predict and to adequately treat. Since IBD is a complex, heterogeneous and unpredictable disease, there is an urgent need for biomarkers, which are objectively measured parameters of (ab)normal biological processes or -systems, which may help to (early) diagnose and classify IBD, to assess disease activity and disease complications, and to accurately predict how a patients’ disease course will develop and/or how a patient will respond to a particular treatment.

My work

My research is focused on the discovery and application of novel biomarker signatures in patients with inflammatory bowel diseases (IBD), while also assessing their potential for therapeutic modulation (e.g., through dietary interventions) and their utility to predict clinical outcomes (e.g., response to established medical treatment). Working at the intersection of gastroenterology, immunology and molecular biology, my strategy is to identify functionally relevant disease markers derived from different biological systems (e.g., the immune system, host genetics, the gut microbiome) and -mechanisms (e.g., inflammatory pathways, oxidative stress and redox signaling, iron metabolism and hypoxia) and carefully examine these signatures through detailed phenotypic patient stratification. By adopting this multi-faceted approach and studying the interplay between different pathophysiological entities, my ultimate aim is to develop and validate clinically applicable prediction models using evidence-based translational biomarkers.

My motivation and vision

My personal motivation originates from my clinical experience with the disease burden of patients with IBD. This impressed me and encouraged me to improve IBD care, starting with developing clinically implementable biomarker-based tools for disease diagnostics, disease activity and behavior, drug response and pre-diagnostic IBD. I noticed that especially the latter is heavily understudied, which puzzled me since I believe that the development of predictive tools holds massive potential for disease prevention and thus would allow patients a longer healthy life. Combining fields of gastroenterology, immunology and molecular biology, I aim to identify and apply biomarkers for early diagnosing IBD and subsequently assess the potential for preventive measures such as lifestyle modifications, dietary interventions and early therapy initiation. Ultimately, my future ambition is to improve patients’ quality of life utilizing molecular biomarker signatures.

I also enjoy working with students (bachelor-, master- and PhD-students) and fellow young scientists, and encouraging them to contribute to science. I am always open to anyone who is interested in doing a research project or scientific internship. For more information about the possibilites, feel free to contact me: a.r.bourgonje@umcg.nl.

Keywords

Biomarkers; inflammatory bowel disease; immune-mediated inflammatory diseases; immunity; oxidative stress; inflammation; fibrosis; redox; autoimmune disorders; intestinal inflammatory diseases; multi-omics; clinical research.

Publications

• Peer-reviewed publications (per 1 Jan 2025): 114 articles, letters and reviews; total citations 4,071, h-index 25, i10-index 46 (Google Scholar statistics)
• A full overview of my publications can be found in Google Scholar or in PubMed

Professional memberships

• Member of the PROMISE (PRediction and PRevention through Omics, Microbiome, Immune System, and Environment) consortium.
• Young GI Association United European Gastroenterology (UEG) (2019-present)
• American Gastroenterological Association (AGA) (2019-present)
• European Crohn's and Colitis Organisation (ECCO) (2019-present)
• International Society of Antioxidants, Nutrition and Health (ISANH) (2019-present)

Honors, Awards, Scholarships and Grants

• 'Y-ECCO Abstract Award' (2025). Award given to the 5 best-ranked abstracts submitted to the European Crohn's and Colitis Organisation (ECCO) conference in Berlin, Germany.
• EU Horizon Innovative Health Initiative (IHI) grant 'INTERCEPT' (101194780) (co-applicant). Awarded €883,000.
• UEG Week Top Abstract Award (among the top 5 UEG Week abstracts in 2024). Awarded €10,000.
• Dioraphte Foundation / Stichting Dioraphte. 'Het ontrafelen van immunologische triggers van een zeldzame ernstige auto-immuunziekte van de galwegen.' Awarded €350,000.
• Nederlandse Vereniging voor Gastro-Enterologie (NVGE) / Dutch Society for Gastroenterology, Gastrointestinale proefschriftprijs 2024 (best thesis award, 2nd prize)
• 'Top 10 Digital Oral Presentation Award' (2024). Award for one of the best oral abstract presentations given at the European Crohn's and Colitis Organisation (ECCO) conference in Stockholm, Sweden.
• 'Y-ECCO Abstract Award' (2024). Award given to the 5 best-ranked abstracts submitted to the European Crohn's and Colitis Organisation (ECCO) conference in Stockholm, Sweden.
• Royal Netherlands Academy of Arts and Sciences / Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) De Boer-Van Staveren Fund. 'Identificatie van immunologische triggers van IgG4-gerelateerde ziekte'. Awarded €50,000.
• Horizon Europe consortium grant 'ID-DarkMatter-NCD' (HORIZON-HLTH-2023-DISEASE-03) (co-applicant). Awarded €850,000.
• Gratama Foundation / Groningen University Fund (GUF) grant. 'Ontrafeling van het antilichaamrepertoire van IgG4-gerelateerde ziekte.' Awarded €25,000.
• NWO Rubicon fellowship grant. 'Early detection of inflammatory bowel disease by high-throughput profiling of the human immune system'. Awarded €115,000.
• PSC Partners 'Seeking a Cure' Foundation grant. 'Unraveling the immune triggers of primary sclerosing cholangitis with and without concomitant inflammatory bowel disease'. Awarded €60,000.

• 'UEG Best Abstract Award' (2022). Award for best abstract presentation in the Translational GI session at United European Gastroenterology Week (UEGW) in Vienna, Austria.
• 'Young-ICC Best IBD Paper Award' (2022). Winner of the 2nd prize of the Young Initiative on Crohn's and Colitis (Young-ICC) organisation for the best IBD paper written by junior IBD scientists from the Netherlands.

• Janssen Pharmaceuticals: Role of the NRF2/Keap1-pathway in inflammatory bowel diseases. Awarded €2,100,000 (co-applicant).
• Gastrostart grant (Dutch Society for Gastroenterology). 'Ontrafeling van het antilichaamrepertoire van patiënten met primair scleroserende cholangitis'. Awarded €10,000.
• Stichting de Cock-Hadders grant for PhD research (2021). Awarded €6,140.
• Stichting de Cock-Hadders grant for PhD research (2020). Awarded €4,000.
• Stichting de Cock-Hadders grant for PhD research (2019). Awarded €6,000.
• 'Best Oral Presentation Award' (2019). Award for best oral presentation held at the Paris Redox World Congress in Paris, France, from the International Society of Antioxidants, Nutrition and Health (ISANH).
• 'Best Abstract Award' DDW (2019). Award for conference abstract presented at the Digestive Disease Week in San Diego, CA, USA, ranking among the best 50 abstract submitted from a total of ~4,000 submissions.
• Stichting de Cock-Hadders grant for PhD research. Awarded €5,200.
• JSM MD-PhD stipend (2017). MD/PhD fellowship from the Junior Scientific Masterclass (JSM) of the University of Groningen. Awarded €82,000.
• Compendium Award (2017). Award for achieving the record-breaking score on the Dutch Progress Test of Medicine (ranking first out of ~12,000 medical students)

Main research lines

Immunological signatures of immune-mediated inflammatory diseases

Leveraging state-of-the-art technologies (e.g. phage-display immunoprecipitation sequencing [PhIP-Seq], B-cell receptor sequencing [BCR-Seq]) I aim to discover novel immune-based biomarkers for immune-mediated inflammatory diseases (IMIDs) such as IBD and primary sclerosing cholangitis (PSC). Nowadays it is possible to comprehensively and systemically characterize humoral immunity in health and disease. Using high-throughput and high-resolution approaches, I aim to find serological antibody signatures that may improve disease diagnostics and the efficacy and safety of therapeutic interventions, as well as pre-diagnostic signatures that may subsequently allow early disease detection with opportunities for prevention.

Some papers that exemplify this research line include the following:

1. Phage-display immunoprecipitation sequencing of the serum antibody epitope repertoire in inflammatory bowel disease reveals distinct antibody signatures
   Bourgonje AR ^*, Andreu-Sánchez S^*, Vogl T, Hu S, Vich Vila A, Gacesa R, Leviatan S, Kurilshikov, Klompus S, Kalka IN, van Dullemen HM, Weinberger A, Visschedijk MC, Festen EAM, Faber KN, Wijmenga C, Dijkstra G, Segal E, Fu J, Zhernakova A, Weersma RK.
   Immunity 2023;S1074-7613(23)00185-1. doi: 10.1016/j.immuni.2023.04.017.
2. Phage-display immunoprecipitation sequencing reveals that genetic, environmental, and intrinsic factors influence variation of human antibody epitope repertoires
   Andreu-Sánchez S^*, Bourgonje AR ^*, Vogl T, Kurilshikov A, Leviatan S, Ruiz Moreno AJ, Hu S, Sinha T, Vich Vila A, Klompus S, Kalka IN, de Leeuw K, Arends S, Jonkers I, Withoff S, Lifelines Cohort Study, Brouwer E, Weinberger A, Wijmenga C, Segal E, Weersma RK, Fu J, Zhernakova A.
   Immunity 2023;S1074-7613(23)00171-1. doi: 10.1016/j.immuni.2023.04.003.
3. Patients With Inflammatory Bowel Disease Show IgG Immune Responses Towards Specific Intestinal Bacterial Genera
   Bourgonje AR, Roo-Brand G, Lisotto P, Sadaghian Sadabad M, Reitsema RD, de Goffau MC, Faber KN, Dijkstra G, Harmsen HJM.
   Frontiers in Immunology 2022;13:842911. doi: 10.3389/fimmu.2022.842911.
4. Antibody signatures in inflammatory bowel disease: current developments and future applications
   Bourgonje AR, Vogl T, Segal E, Weersma RK.
   Trends in Molecular Medicine 2022;28(8):693-705. doi: 10.1016/j.molmed.2022.05.004.
5. Mucosal host-microbe interactions associate with clinical phenotypes in inflammatory bowel disease
   Hu S^*, Bourgonje AR ^*, Gacesa R, Jansen BH, Björk JR, Bangma A, Hidding IJ, van Dullemen HM, Visschedijk MC, Faber KN, Dijkstra G, Harmsen HJM, Festen EAM, Vich Vila A, Spekhorst LM, Weersma RK.
   Nature Communications 2024;15:1470. doi: 10.1038/s41467-024-45855-2.

Exploration of inflammation, oxidative stress and fibrosis as pathophysiological mechanisms for biomarker discovery in IBD

My early research addressed the potential utility of biomarkers of inflammation, fibrosis and oxidative stress for detection and monitoring of inflammatory disease activity and the development of disease complications in patients with IBD. Currently, very few biomarkers exist that are able to accurately reflect disease activity in IBD, while most of them are of insufficient accuracy and utility, emphasizing the need for additional biomarkers. Similarly, it is difficult to forecast the development of disease complications (e.g. fibrostenotic and fistulising disease) in an early stage, which would allow for prompt therapeutic intervention. While searching for biomarkers of disease activity and -complications, it is however crucial to take into account the potential impact of genetics, lifestyle factors, and clinical characteristics of patients on biomarkers in IBD, e.g. through patient stratification. This requires complex analysis of ‘big data’ to expose patient- and phenotype-specific molecular biomarkers in IBD. In addition, I have evaluated the effect of nutritional (e.g. vitamins, dietary fibers) and drug-based (e.g. biologicals) interventions on biomarkers in patients with IBD.

Some papers that exemplify this research line include the following:

1. Increased fecal calprotectin levels in Crohn's disease correlate with elevated serum Th1- and Th17-associated cytokines
   Bourgonje AR, von Martels JZH, de Vos P, Faber KN, Dijkstra G.
   PLoS One 2018;13(2):e0193202. doi: 10.1371/journal.pone.0193202.
2. A Combined Set of Four Serum Inflammatory Biomarkers Reliably Predicts Endoscopic Disease Activity in Inflammatory Bowel Disease
   Bourgonje AR ^*, von Martels JZH^*, Gabriëls RY, Blokzijl T, Buist-Homan M, Heegsma J, Jansen BH, van Dullemen HM, Festen EAM, Ter Steege RWF, Visschedijk MC, Weersma RK, de Vos P, Faber KN, Dijkstra G.
   Frontiers in Medicine 2019;6:251. doi: 10.3389/fmed.2019.00251.
3. Crohn’s Disease in Clinical Remission Is Marked by Systemic Oxidative Stress
   Bourgonje AR, von Martels JZH, Bulthuis MLC, van Londen M, Faber KN, Dijkstra G, van Goor H.
   Frontiers in Physiology 2019;10:499. doi: 10.3389/fphys.2019.00499.
4. Serum Free Thiols Are Superior to Fecal Calprotectin in Reflecting Endoscopic Disease Activity in Inflammatory Bowel Disease
   Bourgonje AR, Gabriëls RY, de Borst MH, Bulthuis MLC, Faber KN, van Goor H, Dijkstra G.
   Antioxidants 2019;8(9):351. doi: 10.3390/antiox8090351.
5. The Effect of Phenotype and Genotype on the Plasma Proteome in Patients with Inflammatory Bowel Disease
   Bourgonje AR ^*, Hu S^*, Spekhorst LM^*, Zhernakova DV, Vich Vila A, Li Y, Voskuil MD, van Berkel LA, Bley Folly B, Charrout M, Mahfouz A, Reinders MJT, van Heck JIP, Joosten LAB, Visschedijk MC, van Dullemen HM, Faber KN, Samsom JN, Festen EAM, Dijkstra G, Weersma RK.
   Journal of Crohn’s and Colitis 2022;16(3):414-429. doi: 10.1093/ecco-jcc/jjab157.
6. Serological biomarkers of type I, III and IV collagen turnover are associated with the presence and future progression of stricturing and penetrating Crohn’s disease
   Bourgonje AR, Alexdóttir MS, Otten AT, Loveikyte R, Bay-Jensen AC, Pehrsson M, van Dullemen HM, Visschedijk MC, Festen EAM, Weersma RK, Karsdal MA, Faber KN, Mortensen JH, Dijkstra G.
   Alimentary Pharmacology & Therapeutics 2022;56(4):675-693. doi: 10.1111/apt.17063.
7. Proteomic analyses do not reveal subclinical inflammation in fatigued patients with clinically quiescent inflammatory bowel disease
   Bourgonje AR, Wichers SJ, Hu S, van Dullemen HM, Visschedijk MC, Faber KN, Festen EAM, Dijkstra G, Samsom JN, Weersma RK, Spekhorst LM.
   Scientific Reports 2022;12(1):14581. doi: 10.1038/s41598-022-17504-5.
8. Long-Term Dietary Patterns Are Reflected in the Plasma Inflammatory Proteome of Patients with Inflammatory Bowel Disease
   Bourgonje AR ^*, Bolte LA^*, Vranckx LLC, Spekhorst LM, Gacesa R, Hu S, van Dullemen HM, Visschedijk MC, Festen EAM, Samsom JN, Dijkstra G, Weersma RK, Campmans-Kuijpers MJE.
   Nutrients 2022;14(12):2522. doi: 10.3390/nu14122522.
9. The effect of riboflavin supplementation on the systemic redox status in healthy volunteers: a post-hoc analysis of the RIBOGUT trial
   Bourgonje AR ^*, Otten AT^*, Sadaghian Sadabad M, von Martels JZH, Bulthuis MLC, Faber KN, van Goor H, Dijkstra G, Harmsen HJM.
   Free Radical Biology and Medicine 2022;190:169-178. doi: 10.1016/j.freeradbiomed.2022.08.008.
10. Hepcidin and Iron Status in Patients With Inflammatory Bowel Disease Undergoing Induction Therapy With Vedolizumab or Infliximab
    Loveikyte R^*, Bourgonje AR ^*, van der Reijden JJ, Bulthuis MLC, Hawinkels LJAC, Visschedijk MC, Festen EAM, van Dullemen HM, Weersma RK, van Goor H, van der Meulen-de Jong AE, Dijkstra G.
    Inflammatory Bowel Diseases 2023;izad010. doi: 10.1093/ibd/izad010.
11. Riboflavin Supplementation in Patients with Crohn’s Disease [the RISE-UP study]
    von Martels JZH^*, Bourgonje AR ^*, Klaassen MAY^*, Alkhalifah HAA, Sadaghian Sadabad, Vich Vila A, Gacesa R, Gabriëls RY, Steinert RE, Jansen BH, Bulthuis MLC, van Dullemen HM, Visschedijk MC, Festen EAM, Weersma RK, de Vos P, van Goor H, Faber KN, Harmsen HJM, Dijkstra G.
    Journal of Crohn’s and Colitis 2020;14(5):595-607. doi: 10.1093/ecco-jcc/jjz208.
12. Vitamin C Supplementation in Healthy Individuals Leads to Shifts of Bacterial Populations in the Gut-A Pilot Study
    Otten AT^*, Bourgonje AR ^*, Peters V, Alizadeh BZ, Dijkstra G, Harmsen HJM.
    Antioxidants 2021;10(8):1278. doi: 10.3390/antiox10081278.

Oxidative stress and redox medicine

In addition to my research dedicated to IBD, I am actively working on a multidisciplinary research line in which we perform translational research in the field of molecular redox biology and oxidative stress as pathophysiological disease mechanism. Oxidative stress is defined as an imbalance oxidants and antioxidants in favor of the oxidants, leading to a disruption of redox signaling and control and/or molecular damage. Oxidative stress plays a pivotal role in various inflammatory- and/or immune-mediated disease, including IBD, but also in cardiovascular-, metabolic- and neuropsychiatric diseases. My studies in this area are focused on the identification of oxidative stress/redox-related biomarkers and investigation of their potential clinical utility in oxidative stress-mediated diseases, ultimately aiming to improve patient stratification and disease management.

Some papers that exemplify this research line include the following:

1. Oxidative Stress and Redox-Modulating Therapeutics in Inflammatory Bowel Disease
   Bourgonje AR, Feelisch M, Pasch A, Faber KN, Dijkstra G, van Goor H.
   Trends in Molecular Medicine 2020;26(11):1034-1046. doi: 10.1016/j.molmed.2020.06.006.
2. Personalized redox medicine in inflammatory bowel diseases: an emerging role for HIF-1α and NRF2 as therapeutic targets
   Bourgonje AR, Klóska D, Grochot-Przęczek A, Feelisch M, Cuadrado A, van Goor H.
   Redox Biology 2023;60:102603. doi: 10.1016/j.redox.2023.102603.
3. Serum free sulfhydryl status associated with new-onset chronic kidney disease in the general population
   Bourgonje AR, Abdulle AE, Bourgonje MF, Binnenmars SH, Gordijn SJ, Bulthuis MLC, la Bastide-van Gemert S, Kieneker LM, Gansevoort RT, Bakker SJL, Mulder DJ, Pasch A, de Borst MH, van Goor H.
   Redox Biology 2023;48:102211. doi: 10.1016/j.redox.2021.102211.
4. Systemic oxidative stress associates with new-onset hypertension in the general population
   Bourgonje AR, Bourgonje MF, Post A, la Bastide-van Gemert S, Kieneker LM, Bulthuis MLC, Gordijn SJ, Gansevoort RT, Bakker SJL, Mulder DJ, Pasch A, van Goor H, Abdulle AE.
   Free Radical Biology and Medicine 2023;187:123-131. doi: 10.1016/j.freeradbiomed.2022.05.020.
5. Plasma Calprotectin Levels Associate with Suspected Metabolic-Associated Fatty Liver Disease and All-Cause Mortality in the General Population
   Bourgonje AR, van den Berg EH, Kieneker LM, Nilsen T, Hidden C, Bakker SJL, Blokzijl H, Dullaart RPF, van Goor H, Abdulle AE.
   International Journal of Molecular Sciences 2022;23(24):15708. doi: 10.3390/ijms232415708.
6. Plasma Neutrophil Gelatinase-Associated Lipocalin Associates with New-Onset Chronic Kidney Disease in the General Population
   Bourgonje AR, Abdulle AE, Bourgonje MF, Kieneker LM, la Bastide-van Gemert S, Gordijn SJ, Hidden C, Nilsen T, Gansevoort RT, Mulder DJ, Dullaart RPF, de Borst MH, Bakker SJL, van Goor H.
   Biomolecules 2023;13(2):338. doi: 10.3390/biom13020338.
7. Plasma levels of GlycA, a pro-inflammatory glycoprotein biomarker, associate with an increased risk of microvascular complications in patients with type 2 diabetes (Zodiac-62)
   Bourgonje AR, van der Vaart A, Gruppen EG, van Goor H, Bakker SJL, Connelly MA, van Dijk PR, Dullaart RPF.
   Endocrine 2023; in press. doi: 10.1007/s12020-023-03319-5.
8. Serum free thiols predict cardiovascular events and all-cause mortality in the general population: a prospective cohort study
   Abdulle AE^*, Bourgonje AR ^*, Kieneker LM, Koning AM, la Bastide-van Gemert S, Bulthuis MLC, Dijkstra G, Faber KN, Dullaart RPF, Bakker SJL, Gans ROB, Gansevoort RT, Mulder DJ, Pasch A, van Goor H.
   BMC Medicine 2020;18(1):130. doi: 10.1186/s12916-020-01587-w.
9. Oxidative stress is associated with suspected non-alcoholic fatty liver disease and all-cause mortality in the general population
   Damba T^*, Bourgonje AR ^*, Abdulle AE, Pasch A, Sydor S, van den Berg EH, Gansevoort RT, Bakker SJL, Blokzijl H, Dullaart RPF, van Goor H, Moshage H.
   Liver International 2020;40(9):2148-2159. doi: 10.1111/liv.14562.
10. Systemic Oxidative Stress, Aging and the Risk of Cardiovascular Events in the General Female Population
    Bourgonje MF, Bourgonje AR, Abdulle AE, Kieneker LM, la Bastide-van Gemert S, Gansevoort RT, Bakker SJL, Pasch A, Saleh J, Gordijn SJ, van Goor H.
    Frontiers in Cardiovascular Medicine 2021;8:630543. doi: 10.3389/fcvm.2021.630543.
11. Serum free thiols in recently diagnosed patients with schizophrenia spectrum disorder: a potentially useful biomarker of oxidative stress
    Borkent J, Ioannou M, Folkertsma TS, Wardenaar KJ, Haarman BCM, van Goor H, Sommer IEC, Bourgonje AR.
    Psychiatry Research 2023;321:115075. doi: 10.1016/j.psychres.2023.115075.
12. A Sex-Specific Comparative Analysis of Oxidative Stress Biomarkers Predicting the Risk of Cardiovascular Events and All-Cause Mortality in the General Population: A Prospective Cohort Study
    Bourgonje MF, Abdulle AE, Kieneker LM, la Bastide-van Gemert S, Bakker SJL, Gansevoort RT, Gordijn SJ, van Goor H, Bourgonje AR.
    Antioxidants 2023;12(3):690. doi: 10.3390/antiox12030690.

Coronavirus disease 2019 (COVID-19)

When I was halfway my MD-PhD trajectory, the coronavirus disease 2019 (COVID-19) pandemic emerged, which posed a major challenge to our society and public health. Simultaneously, it had a great impact on science, and triggered actions to unravel COVID-19 pathophysiology, to develop diagnostic methods, and to deliver therapeutic agents and vaccinations in order to combat the disease. Together with several (inter)national collaborators, this triggered me also to investigate its impact on patients with IBD and the potential contribution of biomarker discovery research. These studies highlighted the consequences of COVID-19 for patients with IBD, and the importance of biobanks and biomarkers in medicine.

Some papers that exemplify this research line include the following:

1. Angiotensin-converting enzyme 2 (ACE2), SARS-CoV-2 and the pathophysiology of coronavirus disease 2019 (COVID-19)
   Bourgonje AR ^*, Abdulle AE^*, Timens W, Hillebrands JL, Navis GJ, Gordijn SJ, Bolling MC, Dijkstra G, Voors AA, Osterhaus ADME, van der Voort PHJ, Mulder DJ, van Goor H.
   Journal of Pathology 2020;251(3):228-248. doi: 10.1002/path.5471.
2. Treatment of severe acute ulcerative colitis in SARS-CoV-2 infected patients: report of three cases and discussion of treatment options
   Bourgonje AR, van Linschoten RCA, West RL, van Dijk MA, van Leer-Buter CC, Kats-Ugurlu G, Pierik MJ, Festen EAM, Weersma RK, Dijkstra G.
   Therapeutic Advances in Gastroenterology 2021;14:17562848211012595. doi: 10.1177/17562848211012595.
3. N-Acetylcysteine and Hydrogen Sulfide in Coronavirus Disease 2019
   Bourgonje AR, Offringa AK, van Eijk LE, Abdulle AE, Hillebrands JL, van der Voort PHJ, van Goor H, van Hezik EJ.
   Antioxidants & Redox Signaling 2021;35(14):1207-1225. doi: 10.1089/ars.2020.8247.
4. The Risk of Developing Long COVID in Patients with Inflammatory Bowel Diseases: Do Immunosuppressive Drugs Matter?
   Bourgonje AR, Otten AT.
   Clinical Gastroenterology and Hepatology 2023;S1542-3565(23)00031-9. doi: 10.1016/j.cgh.2022.12.030.
5. Mild Coronavirus Disease 2019 (COVID-19) Is Marked by Systemic Oxidative Stress: A Pilot Study
   van Eijk LE, Tami A, Hillebrands JL, den Dunnen WFA, de Borst MH, van der Voort PHJ, Bulthuis MLC, Veloo ACM, Wold KI, Vincenti González MF, van der Gun BTF, van Goor H, Bourgonje AR.
   Antioxidants 2021;10(12):2022. doi: 10.3390/antiox10122022.
6. Working towards a comprehensive appraisal of vaccine-induced immunity against SARS-CoV-2 in IBD
   Otten AT^*, Bourgonje AR ^*, Visschedijk MC.
   Lancet Gastroenterology and Hepatology 2023;8(2):99-100. doi: 10.1016/S2468-1253(22)00404-6.
7. Use of Tumor Necrosis Factor-α Antagonists Is Associated With Attenuated IgG Antibody Response Against SARS-CoV-2 in Vaccinated Patients With Inflammatory Bowel Disease
   Otten AT^*, Bourgonje AR ^*, Horinga PP, van der Meulen HH, Festen EAM, van Dullemen HM, Weersma RK, van Leer-Buter CC, Dijkstra G, Visschedijk MC.

   Frontiers in Immunology 2022;13:920333. doi: 10.3389/fimmu.2022.92033.