To STRIDE or not to STRIDE: a critique of "treat to target" in Crohn´s disease.

INTRODUCTION: The STRIDE consensus suggested to focus on mucosal healing, based on biomarkers and endoscopy, in addition to clinical endpoints as treatment target. This narrative review provides a critique of this concept in Crohn´s disease. AREAS COVERED: We analyze and discuss the limitations of endpoints as targets, their currently limited achievability, and the controversial evidence relating to 'treat to target.' The relevant publications in Pubmed were identified in a literature review with the key word 'Crohn´s disease.' EXPERT OPINION: All targets and endpoints have their limitations, and, even if reached, not all have unequivocally been shown to improve prognosis. The major deficiency of STRIDE is not only the lack of validation and agreement upon endpoints but little evidence of their achievability in a sizable proportion of patients by dose or timing adjustments or switching the medication. Above all, the concept should be based on clear evidence that patients indeed benefit from appropriate escalation of treatment and relevant controlled studies in this regard have been controversial. Until the STRIDE approach is proven to be superior to standard treatment focusing on clinical well-being, the field should remain reluctant and expect more convincing evidence before new targets are approved.

Prioritization in inflammatory bowel disease therapy.

INTRODUCTION: Most guidelines for IBD still recommend step-by-step therapy with initially classic drugs such aminosalicylates (in ulcerative colitis) or steroids but avoid prioritizing certain biological drugs and JAK inhibitors in the complicated course. This review provides an aid to pending therapy decisions. AREAS COVERED: In this review, we analyze the evidence for Crohn's disease as well as ulcerative colitis in order to optimize and 'personalize' the choice of therapy, especially in difficult cases. The relevant publications in Pubmed were identified in a continuous literature review with the key words 'Crohn´s disease' and 'ulcerative colitis.' EXPERT OPINION: Based on this complex data set following standard therapies steroid-refractory Crohn´s disease should preferentially be treated with combined infliximab plus azathioprine or risankizumab, in second line after their failure with ustekinumab or 7adalimumab. In steroid-refractory ulcerative colitis infliximab plus azathioprine or upadacitinib should be preferred in first line, filgotinib, tofacitinib or ustekinumab in second line. A steroid-dependent course in both diseases requires azathioprine or vedolizumab, in second line infliximab or Janus kinase inhibitors. The conclusions drawn from these complex data may be helpful for individual decision making in daily clinical practice.

High In-Hospital Mortality in SARS-CoV-2-Infected Patients with Active Cancer Disease during Omicron Phase of the Pandemic: Insights from the CORONA Germany Study.

INTRODUCTION: SARS-CoV-2 infected patients with cancer have a worse outcome including a significant higher mortality, compared to non-cancer patients. However, limited data are available regarding in-hospital mortality during the Omicron phase of the pandemic. Therefore, the aim of the study was the comparison of mortality in patients with history of cancer and patients with active cancer disease during the different phases of the COVID-19 pandemic, focusing on the current Omicron variant of concern. METHODS: We conducted a multicenter, observational, epidemiological cohort study at 45 hospitals in Germany. Until July 20, 2022, all adult hospitalized SARS-CoV-2 positive patients were included. The primary endpoint was in-hospital mortality regarding cancer status (history of cancer and active cancer disease) and SARS-CoV-2 virus type. RESULTS: From March 11, 2020, to July 20, 2022, a total of 27,490 adult SARS-CoV-2 positive patients were included in the study. 2,578 patients (9.4%) had diagnosis of cancer, of whom 1,065 (41.3%) had history of cancer, whereas 1,513 (58.7%) had active cancer disease. Overall 3,749 out of the total of 27,490 patients (13.6%) died during the hospital stay. Patients with active cancer disease had a significantly higher mortality compared to patients without cancer diagnosis, in both phases of the pandemic (wild-type to Delta: OR 1.940 [1.646-2.285]); Omicron: 2.864 [2.354-3.486]). After adjustment to co-variables, SARS-CoV-2 infected patients with active cancer disease had the highest risk for in-hospital mortality compared to the other groups, in both phases of the pandemic. CONCLUSION: The CORONA Germany study indicates that hospitalized patients with active cancer disease are at high risk of death during a SARS-CoV-2 infection. Mortality of patients with history of cancer improved to nearly the level of non-cancer patients during Omicron phase.

Twenty-five years of biologicals in IBD: What´s all the hype about?

Twenty-five years ago the field was revolutionized by the introduction of infliximab as the first hybrid anti-TNF-antibody. Subsequently, other humanized anti-TNFs were developed and marketed, followed by antibodies to new targets including integrins (vedolizumab) and interleukin 12/23 (ustekinumab). All these so-called biologicals were shown in registrational trials to induce remission superior to placebo but consistently were effective in only a minority of patients. Even though in most trials only the responders were selected to continue on the respective medication for maintenance, many experienced a secondary loss of response and only a minority of usually <25% of the initial cohort achieved long-term (1 year) remission. In 'real life studies', the outcome was somewhat better, probably due to proper selection of patients and open, mostly retrospective study designs. A clear benefit of biologicals is apparent in otherwise treatment refractory patients, in extraintestinal manifestations and in Crohn´s disease (CD) with fistulizing complications. Biologicals achieve mucosal healing (MH) more often than corticosteroids or thiopurines, and MH is associated with improved prognosis. However, this does not justify escalating treatment until MH is reached since controlled trials proving this point of 'treat to target' are lacking both in ulcerative colitis and CD. Surgical rates have decreased with increasing use of biologicals, but disease progression has not been proven to improve. With the exception of opportunistic infections, serious adverse events are rare. In conclusion, biologicals have changed the scene considerably and expanded our armamentarium, but there is also a marketing hype fostering expectations without evidence.

Therapeutic peptides in inflammatory bowel disease.

INTRODUCTION: Therapeutic peptides in inflammatory bowel diseases essentially comprise cytokines affecting immune response, growth factors and monoclonal antibodies directed against key targets of mucosal inflammation, in particular, tumor necrosis factor-a (TNF-a). The latter have revolutionized standard medical treatment which previously was restricted to mesalamine, corticosteroids or classical immunosuppressants. AREAS COVERED: We review current evidence of the use of the so-called biologicals, including the well-established TNF-a antagonists and novel peptides and monoclonal antibodies developed for these diseases. The focus is on controlled clinical trials and meta-analyses, if available. Limitations and biases of these studies are important but tend to be ignored. Safety is also an important issue with opportunistic infections and lymphoma as relevant risks. There is significant heterogeneity between different countries, guidelines and opinions within the scientific community regarding clinical indications, even apart from pharmacoeconomics and reimbursement. EXPERT OPINION: TNF blockers have greatly extended medical options in inflammatory bowel diseases. Their more or less extensive use in nearly all patients or only a few selected indications is a matter of debate. It proved difficult to reproduce this success with other antibody targets as well as with immunomodulatory cytokines and growth factors. The most promising novel peptide is vedolizumab, an antibody against α4ß7 integrin.

The debated role for thiopurines in Crohn's disease.

There is a new debate on the role of thiopurines in Crohn's disease. This viewpoint discusses the current evidence and balances thiopurines against other treatment options in the therapeutic algorithm of Crohn's disease.

Differences between treatment guidelines--Germany.

When looking at different treatment guidelines the topics most debated for Crohn's disease are the following: (a) the use of mesalamine for remission induction and maintenance in mild to moderate Crohn's disease; (b) the early use of anti-TNF antibodies in Crohn's disease with or without classical immunomodulators for remission induction, and (c) remission induction in steroid-refractory disease with anti-TNF antibodies or calcineurin inhibitors. The topics mentioned above will be discussed with regard to the statements of the German Gastroenterology Association (DGVS) on the basis of the underlying evidence.

Mucosal improvement in patients with moderate to severe postoperative endoscopic recurrence of Crohn's disease and azathioprine metabolite levels.

BACKGROUND: The value of azathioprine metabolites (6-thioguanine nucleotides [6-TGN]) in monitoring clinical treatment response is still controversially discussed. Data regarding thiopurine metabolite levels and endoscopic improvement are lacking. METHODS: Data were analyzed post hoc from a 1-year, multicenter, double-blind, double-dummy, randomized trial comparing azathioprine 2.0 to 2.5 mg/kg per day versus mesalamine 4 g/d in a subset of 23 postoperative patients with Crohn's disease (CD) treated with azathioprine and having moderate-to-severe endoscopic recurrence according to a modified 6-grade score. Red blood cell (RBC) concentrations of 6-TGN, 6-methyl-mercaptopurine ribonucleotides (6-MMPR), and 6-methyl-thioguanine nucleotides (6-MTGN) were indicated as follows: area under the concentration-time curve, average concentration (C av), and concentration at the final study visit. RESULTS: Overall, 74% of patients showed an improvement in the modified endoscopic score (P = 0.022). Median endoscopic score reduced from 4 at the baseline to 2 at the final visit. Patients with a high C av for 6-TGN (≥ 193 pmol/8 × 10(8) RBC; P = 0.017) or 6-MTGN (≥ 79.2 pmol/8 × 10(8) RBC; P = 0.035) significantly improved in endoscopic score, and the improvement in endoscopic score correlated with C av for 6-TGN (r = -0.51; P = 0.013). For concentration at the final visit, higher values for 6-TGN (≥ 142 pmol/8 × 10(8) RBC; P = 0.017) were associated with a better postoperative score. Sensitivity analysis revealed a significant correlation between 6-TGN (area under the concentration-time curve) and postoperative endoscopic improvement. CONCLUSIONS: Our post hoc analysis from a double-blind, randomized trial suggests that higher RBC 6-TGN levels are associated with endoscopic improvement in patients with severe postoperative endoscopic recurrence of CD. Thus, our study provides first evidence on the utility of monitoring of thiopurine metabolites to achieve mucosal response in CD.

Azathioprine versus mesalazine for prevention of postoperative clinical recurrence in patients with Crohn's disease with endoscopic recurrence: efficacy and safety results of a randomised, double-blind, double-dummy, multicentre trial.

OBJECTIVE: The aim of the study was to compare azathioprine versus mesalazine tablets for the prevention of clinical recurrence in patients with postoperative Crohn's disease (CD) with moderate or severe endoscopic recurrence. METHODS: This was a 1 year, double-blind, double-dummy, randomised study which took place in 21 gastroenterology centres in Austria, the Czech Republic, Germany and Israel. The study participants were 78 adults with CD who had undergone resection with ileocolonic anastomosis in the preceding 6-24 months without subsequent clinical recurrence and with a Crohn's disease activity index (CDAI) score <200, but with moderate or severe endoscopic recurrence. The study drugs were azathioprine 2.0-2.5 mg/kg/day or mesalazine 4 g/day over 1 year. The primary end point was therapeutic failure during 1 year, defined as a CDAI score > or = 200 and an increase of > or = 60 points from baseline, or study drug discontinuation due to lack of efficacy or intolerable adverse drug reaction. RESULTS: Treatment failure occurred in 22.0% (9/41) of azathioprine-treated patients and 10.8% (4/37) of mesalazine-treated patients, a difference of 11.1% (95% CI -5.0% to 27.3%, p=0.19). Clinical recurrence was significantly less frequent with azathioprine versus mesalazine (0/41 (0%) vs 4/37 (10.8%), p=0.031), whereas study drug discontinuation due to adverse drug reactions only occurred in azathioprine-treated patients (9/41 (22.0%) vs 0%, p=0.002). The proportion of patients showing > or = 1 point reduction in Rutgeerts score between baseline and month 12 was 63.3% (19/30) and 34.4% (11/32) in the azathioprine and mesalazine groups, respectively (p=0.023). CONCLUSIONS: In this population of patients with postoperative CD at high risk of clinical recurrence, superiority for azathioprine versus mesalazine could not be demonstrated for therapeutic failure.

Genetic variants of Wnt transcription factor TCF-4 (TCF7L2) putative promoter region are associated with small intestinal Crohn's disease.

Reduced expression of Paneth cell antimicrobial alpha-defensins, human defensin (HD)-5 and -6, characterizes Crohn's disease (CD) of the ileum. TCF-4 (also named TCF7L2), a Wnt signalling pathway transcription factor, orchestrates Paneth cell differentiation, directly regulates the expression of HD-5 and -6, and was previously associated with the decrease of these antimicrobial peptides in a subset of ileal CD. To investigate a potential genetic association of TCF-4 with ileal CD, we sequenced 2.1 kb of the 5' flanking region of TCF-4 in a small group of ileal CD patients and controls (n = 10 each). We identified eight single nucleotide polymorphisms (SNPs), of which three (rs3814570, rs10885394, rs10885395) were in linkage disequilibrium and found more frequently in patients; one (rs3814570) was thereby located in a predicted regulatory region. We carried out high-throughput analysis of this SNP in three cohorts of inflammatory bowel disease (IBD) patients and controls. Overall 1399 healthy individuals, 785 ulcerative colitis (UC) patients, 225 CD patients with colonic disease only and 784 CD patients with ileal involvement were used to determine frequency distributions. We found an association of rs3814570 with ileal CD but neither with colonic CD or UC, in a combined analysis (allele positivity: OR 1.27, 95% CI 1.07 to 1.52, p = 0.00737), which was the strongest in ileal CD patients with stricturing behaviour (allele frequency: OR 1.32, 95% CI 1.08 to1.62, p = 0.00686) or an additional involvement of the upper GIT (allele frequency: OR 1.38, 95% CI 1.03 to1.84, p = 0.02882). The newly identified genetic association of TCF-4 with ileal CD provides evidence that the decrease in Paneth cell alpha-defensins is a primary factor in disease pathogenesis.

A systematic survey evaluating 6-thioguanine-related hepatotoxicity in patients with inflammatory bowel disease.

OBJECTIVE: Drug-induced liver injury was recently reported as a major complication leading to hepatic nodular regenerative hyperplasia (NRH) in patients with inflammatory bowel disease (IBD) and 6-thioguanine (6-TG) therapy. The aim of the study was to evaluate the prevalence of 6-TG-related hepatotoxicity in a large multi-centered IBD population by means of a systematic online survey. METHODS: Clinical and laboratory data, imaging techniques (sonography, CT, MRI) and histology of liver biopsies were surveyed in IBD patients treated with 6-TG. The decision on whether liver imaging and/or liver biopsy were performed was exclusively at the discretion of the investigator. RESULTS: 6-TG use was fully documented in 296 patients (median treatment duration 56 weeks, range < 1-207). Laboratory signs of drug-induced liver injury were found in 43 patients (14.5%). Liver imaging revealed pathologic results in 68/176 patients (38.6%). Liver biopsy was performed in a subset of 60 patients; using silver-reticulin staining (n = 59), NRH was considered in 16 patients (27.1%). Age was the only independent, albeit weak, risk factor for development of NRH. CONCLUSION: This large online survey confirms the strong association between 6-TG treatment and the significant risk of development of NRH in patients with IBD. The definitive diagnosis of NRH depends solely upon liver biopsy.

Randomized, double blind controlled trial of subcutaneous recombinant human interleukin-11 versus prednisolone in active Crohn's disease.

BACKGROUND: Interleukin-11 has shown benefit in animal inflammatory bowel disease models. Recently, recombinant human interleukin-11 (rhIL-11) has been observed to induce remission in a subset of patients with mild to moderate Crohn's disease (CD). The present study compared the efficacy of rhIL-11 versus prednisolone in remission induction in CD. METHODS: Patients with active CD were randomly assigned to receive either subcutaneous rhIL-11 (1 mg once weekly) and prednisolone placebo tablets, or active prednisolone (60 mg/day) and rhIL-11 placebo, for 12 weeks. Prednisolone/placebo was tapered after week 1, and patients were assessed every second week. RESULTS: Fifty-one patients received medication: 13/27 (rhIL-11) and 17/24 (prednisolone) completed 12 weeks of treatment. Remission rates (intent to treat) for rhIL-11 versus prednisolone were 4% versus 46% at week 4 (p < 0.001) and 19% versus 50% at week 6 (p < 0.05). Response to treatment (deltaCDAI > 100) was seen in 19% (rhIL-11) versus 63% (prednisolone) after 4 weeks (p < 0.002) and 37% versus 63% after 6 weeks (p = 0.1). After 12 weeks of treatment, it was observed that 22% (rhIL-11) versus 21% (prednisolone) had remained in remission. Frequent side effects of rhIL-11 included fever (n = 3), rash (4), arthralgia/arthritis (3), nausea/vomiting (3), and headache (6). CONCLUSION: rhIL-11 is well tolerated but significantly inferior when compared to prednisolone in short-term remission induction in patients with active CD. In this patient cohort, both treatments appeared to be poor in maintaining remission over a period of 3 months.

The pharmacogenetics of methotrexate in inflammatory bowel disease.

OBJECTIVES: Methotrexate (MTX) is an effective immunosuppressive treatment in inflammatory bowel disease (IBD) but its use is limited by unpredictable toxicity and efficacy. MTX metabolism is complex involving a number of enzymes. An individual's response to MTX may in part be genetically determined by functional genetic variation in genes encoding these enzymes. We report a pharmacogenetic evaluation of MTX therapy in IBD. METHODS: We studied 102 IBD patients treated with MTX, and 202 patients with Crohn's disease (CD), 205 patients with ulcerative colitis (UC) and 189 healthy volunteers served as controls to assess allele frequencies in the disease and healthy populations. All subjects were genotyped for four polymorphisms: G80A in the reduced folate carrier (RFC1) gene, G452T in the gamma-glutamyl hydrolase (GGH) gene and C677T and A1298C in the methylenetetrahydrofolate reductase (MTHFR) gene. Three non-conservative SNPs in the RFC1 and the MTHFR gene could not be detected in our patient cohort. Genotype-phenotype associations were evaluated with respect to efficacy and toxicity of MTX therapy. RESULTS: No significant differences in the allele frequencies between CD, UC and healthy controls were detected. Overall 21% of patients experienced MTX side effects. Patients homozygous for the MTHFR 1298C allele were more likely to experience one or more side effects compared to patients with the wild-type 1298AA genotype (21.0 vs. 6.3%, P < 0.05). None of the genotyped SNPs or haplotypes, either alone or in combination, was associated with short-term efficacy or sustained response. CONCLUSIONS: Side effects of MTX in IBD are associated with a SNP in the MTHFR gene but response cannot be predicted by any of the investigated SNPs.

Fatal staphylococcal sepsis in Crohn's disease after infliximab.

We report a case of a 40-year-old woman who had received infliximab for perianal Crohn's disease. After six infusions of infliximab, the patient developed staphylococcal pneumonia resulting in fatal adult respiratory distress syndrome. The case is discussed in the context of the toxicity profile of infliximab.

Serum procalcitonin differentiates inflammatory bowel disease and self-limited colitis.

BACKGROUND: The distinction between idiopathic inflammatory bowel disease (IBD) and infectious, usually self-limited enterocolitis is still a diagnostic dilemma. Procalcitonin (PCT) is the prohormone of calcitonin and is considered a specific marker of bacterial infection. The aim of this prospective study was to determine the value of PCT in differentiating flares of IBD from self-limited colitis. In addition, because standard laboratory inflammatory parameters are poorly correlated with disease activity in IBD, the relation between PCT levels and disease activity was investigated. METHODS: A total of 76 patients (26 Crohn's disease, CD; 25 ulcerative colitis, UC; and 25 patients with self-limited enterocolitis) were enrolled. Serum levels of PCT were measured by a sandwich immunoluminometric assay. C-reactive protein (CRP) levels, white blood cell counts, and stool cultures were obtained from all patients. Disease activity was assessed by the Crohn's disease activity index (CDAI) and the Truelove index for CD and UC, respectively. RESULTS: Patients with self-limited enterocolitis showed significantly higher PCT levels when compared with IBD patients (0.36 ng/mL, range 0.18-1.7 vs 0.10 ng/mL, range 0.08 0.5, p < 0.001). For a PCT value of > or =0.4, the sensitivity for self-limited colitis was 92% and specifity 96%. The positive predictive value (PPV) for self-limited colitis was 96%, whereas the negative predictive value (NPV) was 93%. In IBD patients, PCT levels were in the normal range although significantly higher in active disease when compared with inactive disease (0.13 ng/mL, range 0.08-0.5 vs 0.09 ng/mL, range 0.08-0.15, p < 0.001). This difference was less pronounced for CD (0.11 ng/mL, range 0.08-0.2 vs 0.09 ng/mL, range 0.08-0.15, p < 0.05) than for UC (0.14 ng/mL, range 0.08-0.5 vs 0.09 ng/mL, range 0.08-0.11, p < 0.01). In CD, PCT levels correlated significantly 0.5, p < 0.01). with the CDAI (r =0.05, p <0.01). CONCLUSIONS: The measurement of PCT offers two diagnostic options in IBD. Supranormal levels indicate self-limited enterocolitis. Furthermore, although within the normal range in IBD, PCT levels may serve as a new serological marker of disease activity.

Inducible and constitutive beta-defensins are differentially expressed in Crohn's disease and ulcerative colitis.

Antimicrobial peptides such as defensins provide nonspecific mucosal defense against a multitude of microorganisms. Recently, it has been shown that luminal bacteria may invade the mucosa in inflammatory bowel diseases, suggesting a defect in innate mucosal immunity. The aim of this study was to investigate the expression of human beta-defensins (HBD) in controls, Crohn's disease (CD), ulcerative colitis (UC), and unspecific inflammation. Up to 4 biopsies were taken from 103 patients (33 controls, 24 with Crohn's disease, 36 with ulcerative colitis, 10 with unspecific colitis). Mucosal mRNA was measured using real-time fluorescence temperature cycler reverse-transcription polymerase chain reaction with primers for HBD-1, HBD-2, HBD-3, tumor necrosis factor alpha, and interleukin 8. Mucosal HBD-1 expression was marginally decreased in both CD and UC. HBD-2 was increased exclusively in UC but not in CD. The expression of the novel defensin HBD-3 was strongly correlated with HBD-2 and also raised predominantly in UC. The expression of both inducible beta-defensins was enhanced in the state of inflammation. Expression of HBD-2 showed a weak correlation with interleukin 8 only in inflamed CD biopsies but not with tumor necrosis factor alpha. The missing induction of both inducible beta-defensins in CD as compared with UC may cause a defect in barrier function that predisposes to bacterial invasion.

Crohn's disease: a defensin deficiency syndrome?

This comprehensive review promotes the novel concept that a defensin deficiency, i.e. lack of mucosal peptide antibiotics, may play a pivotal role in the aetiopathogenesis of Crohn's disease. Such an impaired function of this chemical barrier is consistent with the epidemiological relationship of good domestic hygiene with the incidence of inflammatory bowel diseases. The disregulated adaptive immune system, formerly believed to be the major cause in the development of Crohn's disease, may reflect only the primary break of the mucosal defence since the immune response is mostly directed against lumenal bacteria. Recent work has identified five different defensins expressed in colonic mucosa. In contrast to ulcerative colitis, Crohn's disease is characterised by an impaired induction of human beta defensins 2 and 3. This deficient induction may be due to changes in the intracellular transcription by NFkappaB and the intracellular peptidoglycan receptor NOD2, mutated in Crohn's disease. These findings are consistent with the mucosal attachment of lumenal bacteria in inflammatory bowel diseases and the frequent occurrence of other infectious agents. The hypothesis of an impaired mucosal antibacterial activity is also consistent with the benefit from antibiotic or probiotic treatment in certain inflammatory bowel disease states.

Human beta-defensin 2 but not beta-defensin 1 is expressed preferentially in colonic mucosa of inflammatory bowel disease.

OBJECTIVE: Various antimicrobial peptides such as defensins are part of innate immunity and contribute to the intestinal barrier that may be defective in inflammatory bowel disease (IBD). This study investigated beta-defensin mRNA and peptide expression in the colon from controls and patients with Crohn's disease, ulcerative colitis or unspecific colitis as inflammatory controls. METHODS: Mucosal mRNA expression was measured by multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) with primers for human beta-defensin 1 (HBD-1) and human beta-defensin 2 (HBD-2) in CaCo-2 cells and in biopsies from 103 patients (33 controls, 24 Crohn's disease patients, 36 ulcerative colitis patients, 10 unspecific colitis patients). Paraffin-embedded tissue from colonic resections was tested for HBD-1 and HBD-2 peptides by immunohistochemistry. RESULTS: HBD-1 mRNA was expressed constitutively whereas HBD-2 was induced by pro-inflammatory cytokines in CaCo-2 cells. HBD-1 mRNA was detectable in 61% of control and Crohn's disease biopsies and 53% of ulcerative colitis biopsies. HBD-2 transcript was expressed differentially, with 18% of control biopsies positive as opposed to 34% in Crohn's disease and 53% in ulcerative colitis. HBD-2 mRNA but not HBD-1 mRNA was expressed preferentially in inflamed areas. Immunohistochemical investigation demonstrated the presence of defensin peptides in colonic epithelium as well as the differential induction in IBD. CONCLUSIONS: HBD-1 is expressed constitutively in colonic tissue irrespective of inflammation. HBD-2 is barely present in uninflamed colon but it is induced in inflammation. The lower expression of HBD-2 in Crohn's disease compared with ulcerative colitis indicates different responses of the mucosal innate defence. Defensins may play a crucial role in controlling pathogen invasion in IBD, although the functional significance remains to be established.