Pilot feasibility studies of leukocytapheresis with the Adacolumn Apheresis System in patients with active ulcerative colitis or Crohn disease

Targeting neutrophils in inflammatory bowel disease: revisiting the role of adsorptive granulocyte and monocyte apheresis

INTRODUCTION

Inflammatory bowel disease (IBD) is a chronic immune-mediated disease of the gastrointestinal tract comprising Crohn's disease (CD) and ulcerative colitis (UC). While any part of the digestive tract can be affected in CD, mucosal inflammation in UC is limited to the colon. Differences and similarities between the two conditions are reflected by their pathophysiology.

AREAS COVERED

An overview of immunological aspects, pharmacological management, and biomarkers of IBD is provided. The role of adsorptive granulocyte and monocyte apheresis (GMA) is reviewed including its primary and secondary effects on the immune system, as well as clinical studies in IBD (mainly UC), and potential biomarkers for adsorptive GMA.

EXPERT OPINION

In UC, adsorptive GMA with Adacolumn (Adacolumn®, JIMRO Co., Ltd. Takasaki, Gunma, Japan) selectively depletes elevated myeloid lineage leukocytes and has a range of beneficial secondary immune effects. Adsorptive GMA is a safe and effective non-pharmacological treatment option for UC. Pilot studies have reported promising results for adsorptive GMA in combination with biological agents, although larger studies are required. Fecal calprotectin concentrations, neutrophil counts in histological samples and/or the neutrophil/lymphocyte ratio in peripheral blood may prove to be useful biomarkers for predicting GMA effectiveness in the future.

Retrospective Single Center Study of Granulocyte Monocyte Adsorption Apheresis Treatment in Inflammatory Bowel Disease

Patients with active inflammatory bowel disease (IBD) have elevated and activated myeloid leukocytes, which infiltrate the intestinal mucosa. A significant proportion of IBD patients do not respond adequately to conventional treatment regimes. Studies have suggested that treatment with granulocyte monocyte apheresis (GMA) could be a safe and efficacious alternative for these patients. We evaluated the efficacy and safety of granulocyte/monocyte apheresis in patients with IBD in a retrospective cohort study, conducted from a single center in Stockholm. Clinical details from consecutive apheresis treated patients were retrospectively reviewed from 2004 to 2012. A total of 37 patients were included, 23 patients with ulcerative colitis (UC) and 14 with Crohn's disease (CD). Clinical response was seen in 11 patients (30%) and complete remission in 11 patients (30%). The remission rate was higher in UC patients compared to CD patients, 39% (N = 9) and 14% (N = 2) respectively. A total of 9 patients experienced adverse events. Most frequently reported was headache (N = 4). GMA seems to be a valuable adjuvant treatment regime in the care of patients with refractory IBD.

Advantages of fecal lactoferrin measurement during granulocyte and monocyte adsorptive apheresis therapy in ulcerative colitis

BACKGROUND

Fecal lactoferrin has been introduced as a useful tool for the diagnosis and monitoring of inflammatory bowel disease (IBD). The aim of this study was to assess if fecal lactoferrin can be employed to predict or estimate the effect of granulocyte and monocyte adsorptive apheresis (GMA) in ulcerative colitis (UC).

METHODS

This was a prospective study involving 21 patients with UC. Patients with moderately-to-severely active UC who were scheduled to undergo GMA were recruited. Changes in fecal lactoferrin concentration were compared between the GMA-responder and -nonresponder groups.

RESULTS

In the GMA-responder group, fecal lactoferrin significantly increased 1 week after the introduction of GMA and then significantly decreased after GMA sessions. Fecal lactoferrin concentrations were significantly higher in the GMA-responder group than in the GMA-nonresponder group at 1 and 2 weeks after the introduction of GMA. Multivariate logistic regression analysis revealed that fecal lactoferrin concentration 1 week after the introduction of GMA was the most contributing factor for the effectiveness of GMA in patients with UC.

CONCLUSIONS

In the GMA-responder group, fecal lactoferrin concentration significantly increased 1 week after the introduction of GMA. Fecal lactoferrin may be beneficial for predicting clinical response of GMA in patients with UC at an early stage of GMA treatment.

Current scenario in inflammatory bowel disease: drug development prospects

BACKGROUND

Inflammatory bowel disease (IBD) pathophysiology have led to the development of various compounds that might ameliorate the disease process. Recently several failures in terms of developing disease-modifying therapies needs to be communicated effectively as per their process and cause which have led to a debate about the potential deficiencies in our understanding of the pathogenesis of IBD and choice of therapeutic targets. So that the thoroughly development of drug candidates and study design of clinical trials is done.

METHODS

Various online medical databases were searched for relevant study and publications. Different clinical trials were reviewed and the available data in clinical trials describing the effective drug development status of IBD medications.

RESULTS

The aminosalicylates, anti-inflammatory and biological molecules tested for the treatment of Crohn's disease (CD) and ulcerative colitis (UC) but the risks of common and rare adverse events were found with treatment. Antibiotics and steroid help in reducing the immune response but further studies required on each molecule to substantiate treatment strategies. There has been significant research on different drug molecules as per the phase, which is summarized in this review.

CONCLUSIONS

Preclinical research on the complex IBD puzzle coupled with an active and vibrant research agenda in recent decades which might reveal patterns of pharmacological interactions instead of single potential drug targets. The increased collaboration between pharmaceutical companies, basic researchers and clinical researchers has the potential to bring us closer to developing an optimum pharmaceutical approach for the treatment of IBD.

A large-scale, prospective, observational study of leukocytapheresis for ulcerative colitis: treatment outcomes of 847 patients in clinical practice

BACKGROUND AND AIMS

Leukocytapheresis is an extracorporeal therapy for ulcerative colitis. However, no large-scale study on leukocytapheresis has been reported. This large-scale, prospective, observational study aimed to evaluate the treatment outcomes of leukocytapheresis for active ulcerative colitis in clinical practice.

METHODS

Patients with active ulcerative colitis treated with leukocytapheresis using a Cellsorba E column between May 2010 and December 2012 were enrolled from 116 medical facilities in Japan.

RESULTS

A total of 847 patients were enrolled, and 623 were available for efficacy analysis. Out of 847 patients, 80.3% of the patients had moderate to severe disease activity, and 67.6% were steroid refractory. As concomitant medications, 5-aminosalicylic acids, corticosteroids, and thiopurines were administered to 94.8%, 63.8%, and 32.8% of the patients, respectively. In addition, infliximab and tacrolimus were concomitantly used in 5.8% and 12.3%, respectively. Intensive leukocytapheresis (≥4 leukocytapheresis sessions within the first 2 weeks) was used in >70% of the patients. Adverse events were seen in 10.3% (87/847), which were severe in only 5 patients (0.6%). Any concomitant medications did not increase the incidence of adverse events. Intensive leukocytapheresis was as safe as the conventional weekly procedure. The overall clinical remission rate was 68.9% (429/623), and the mucosal healing rate was 62.5% (145/232). Clinical remission was achieved more frequently and rapidly in the intensive group than in the weekly group.

CONCLUSIONS

This large-scale study indicates that leukocytapheresis, including intensive procedure, is a safe and effective therapeutic option for active ulcerative colitis.

Granulocytapheresis in steroid-dependent and steroid-resistant patients with inflammatory bowel disease: a prospective observational study

BACKGROUND

Despite the mounting importance of granulocytapheresis (GCAP) for inflammatory bowel disease (IBD) treatment, its effectiveness in steroid-dependent (SD) and steroid-resistant (SR) patients has not been clearly evaluated. This prospective observational study describes the use of GCAP in SD and SR patients with either Ulcerative Colitis (UC) or Crohn's Disease (CD).

METHODS

118 patients, 83 affected by UC (55 SD and 28 SR) and 35 by CD (22 SD and 13 SR), were treated with GCAP, using Adacolumn™, for 5 consecutive weeks, 1 session/week. All patients were followed for 12 months after the end of GCAP. Clinical remission was defined as Clinical Activity Index (CAI) ≤6 for UC patients and Crohn's Disease Activity Index (CDAI) <150 for CD patients.

RESULTS

All patients completed the study; no major complications were reported. At the end of GCAP 71% of UC and 63% of CD patients showed clinical remission. At 6 months the remission was maintained by 66% and 54% of UC and CD patients respectively, while at 12 months the percentages were 48% and 43%, respectively. No differences between SD and SR subgroups were reported at any timepoint. CAI and CDAI values significantly dropped after GCAP treatment and at 6 and 12 months' follow-up (p<0.05 vs baseline for both timepoints). No differences were measured in CAI and CDAI between SD and SR patients.

CONCLUSION

GCAP therapy is safe and effective in inducing and maintaining clinical remission both in SD and in SR patients affected by either UC or CD.

A randomised, double-blind, sham-controlled study of granulocyte/monocyte apheresis for moderate to severe Crohn's disease

OBJECTIVES

Activated granulocytes and monocytes may contribute to the pathogenesis of Crohn's disease (CD). In small, uncontrolled studies, granulocyte/monocyte apheresis (GMA) has shown promise in treating CD. We conducted a randomised, double-blind study to compare GMA with a sham procedure in patients with moderate to severe CD.

DESIGN

Patients with active CD as defined by a Crohn's Disease Activity Index (CDAI) of 220-450 were randomly allocated in a 2:1 ratio to treatment with GMA using the Adacolumn Apheresis System (JIMRO, Takasaki, Japan) or sham apheresis. Ten apheresis sessions were scheduled over a 9-week period, and efficacy was evaluated at week 12. The primary end point was the proportion of patients achieving clinical remission (CDAI score ≤ 150 without use of prohibited drugs).

RESULTS

Clinical remission was achieved by 17.8% of patients in the GMA group (n = 157) compared with 19.2% of those in the sham control group (n = 78) (absolute difference--1.4% (95% CI--12.8% to 8.5%), p = 0.858). Clinical response (defined as a ≥ 100-point decrease in CDAI) was achieved by 28.0% and 26.9% of patients in the GMA and sham groups, respectively (p = 1.000). The two treatments produced similar changes from baseline in CDAI and quality of life, as well as in disease severity assessed endoscopically. The incidence and types of adverse events did not differ between groups.

CONCLUSIONS

GMA was well tolerated, but this study did not demonstrate its effectiveness over a sham procedure in inducing clinical remission or response in patients with moderate to severe CD.

Long-term follow-up with Granulocyte and Monocyte Apheresis re-treatment in patients with chronically active inflammatory bowel disease

Background

Patients with IBD and chronic inflammation refractory to conventional therapy often demonstrate higher risk of serious complications. Combinations of immunosuppression and biological treatment as well as surgical intervention are often used in this patient group. Hence, there is need for additional treatment options. In this observational study, focused on re-treatment and long-term results, Granulocyte/Monocyte Adsorption (GMA, Adacolumn^®) treatment has been investigated to study efficacy, safety and quality of life in IBD-patients with chronic activity.

Methods

Fifteen patients with ulcerative colitis and 25 patients with Crohn's disease, both groups with chronically active inflammation refractory to conventional medication were included in this observational study. The patients received 5-10 GMA sessions, and the clinical activity was assessed at baseline, after each completed course, and at week 10 and 20 by disease activity index, endoscopy and quality of life evaluation. Relapsed patients were re-treated by GMA in this follow-up study up to 58 months.

Results

Clinical response was seen in 85% and complete remission in 65% of the patients. Ten patients in the UC-group (66%) and 16 patients in the CD-group (64%) maintained clinical and endoscopic remission for an average of 14 months. Fourteen patients who relapsed after showing initial remission were re-treated with GMA and 13 (93%) went into a second remission. Following further relapses, all of seven patients were successfully re-treated for the third time, all of three patients for the fourth time and one for a fifth time.

Conclusions

IBD-patients with chronic inflammation despite conventional therapy seem to benefit from GMA. Re-treatment of relapsing remission patients seems to be effective.

Leukocyte apheresis in the management of ulcerative colitis

Ulcerative colitis is a chronic inflammatory disease that affects the colon and rectum. Its pathogenesis is probably multifactorial including the influx of certain cytokines into the colonic mucosa, causing disease activity and relapse. The hypothesis of removing such cytokines from the circulation by leukocytapheresis was implemented to reduce disease activity, maintain remission, and prevent relapse. Many recent reports not only in Japan, but also in the West, have highlighted its beneficial effects in both adult and pediatric patients. Large placebo-controlled studies are needed to confirm the available data in this regard. In this article, we shed some light on the use of leukocyte apheresis in the management of autoimmune diseases, especially ulcerative colitis.

Adenosine: An immune modulator of inflammatory bowel diseases

Inflammatory bowel disease (IBD) is a common and lifelong disabling gastrointestinal disease. Emerging treatments are being developed to target inflammatory cytokines which initiate and perpetuate the immune response. Adenosine is an important modulator of inflammation and its anti-inflammatory effects have been well established in humans as well as in animal models. High extracellular adenosine suppresses and resolves chronic inflammation in IBD models. High extracellular adenosine levels could be achieved by enhanced adenosine absorption and increased de novo synthesis. Increased adenosine concentration leads to activation of the A2a receptor on the cell surface of immune and epithelial cells that would be a potential therapeutic target for chronic intestinal inflammation. Adenosine is transported via concentrative nucleoside transporter and equilibrative nucleoside transporter transporters that are localized in apical and basolateral membranes of intestinal epithelial cells, respectively. Increased extracellular adenosine levels activate the A2a receptor, which would reduce cytokines responsible for chronic inflammation.

Granulocytapheresis in the treatment of patients with active ulcerative colitis

In recent years, considering the role of inflammatory processes and the involvement of the immune system in ulcerative colitis, granulocytapheresis, a technique for removing circulating leukocytes and preventing their migration into the intestinal mucosa, has been proposed for the treatment of acute ulcerative colitis. Initially introduced for the treatment of patients who did not respond to conventional therapy only, this new therapy may become a useful and safe method to induce clinical remission in patients with acute disease. This article will review the clinical applications and issues concerning the use of granulocytapheresis in ulcerative colitis.

US estimates of hospitalized pediatric patients with ulcerative colitis: implications for multicenter clinical studies

BACKGROUND

The optimal clinical management of children hospitalized with ulcerative colitis (UC) is evolving. There are limited data quantifying the number of pediatric patients with UC admitted to hospitals in the United States. We analyzed the Kids' Inpatient Database (KID, 2003), to estimate the distribution of hospitalized children with UC and estimate sample sizes available for clinical research.

METHODS

We limited our analysis to subjects age less than 18 years. We defined cases of UC as discharge records associated with an ICD-9 code of 556.0-556.9 in the first position. We defined colectomy as principal procedure code of 45.8. We generated weighted estimates for these analyses. To estimate the relationship between number of patients and number of hospitals necessary for clinical trials, we generated 1000 simulated datasets.

RESULTS

A total of 2311 UC cases were identified. The mean age at admission was 13.1 (standard error [SE] 0.1) years, and 9% (SE 0.9%) underwent colectomy during their hospitalization. 1008 UC cases were treated at high-volume hospitals; the majority of these children were treated at children's hospitals. Simulation studies suggest that approximately 5 high-volume hospitals would be necessary to generate sample sizes necessary for a pilot clinical trial of refractory UC.

CONCLUSIONS

Approximately half of all young patients hospitalized with UC in the US were treated at a limited number of high-volume hospitals, and approximately 5 such centers would be adequate for pilot clinical trials of hospitalized patients with refractory UC.

A randomized, double-blind, sham-controlled study of granulocyte/monocyte apheresis for active ulcerative colitis

BACKGROUND & AIMS

Activated granulocytes and monocytes/macrophages are implicated in the pathogenesis of ulcerative colitis. Open-label studies and clinical experience in Japan and Europe have suggested that granulocyte/monocyte apheresis is safe and effective in treating ulcerative colitis.

METHODS

We evaluated the efficacy of granulocyte/monocyte apheresis in a randomized, double-blind, sham-controlled trial in patients with active moderate-to-severe ulcerative colitis (Mayo score 6-11) in community-based and tertiary care centers. As intervention, we used granulocyte/monocyte apheresis with the Adacolumn Apheresis System (JIMRO, Ltd, Takasaki, Japan) or sham apheresis in a 2:1 ratio for 9 weeks of treatment in a North American pivotal study (N = 168) and in a smaller, companion study of identical design conducted in Europe and Japan (N = 47).

RESULTS

In the pivotal study, clinical remission rates (Mayo score 0-2, with scores of 0 on rectal bleeding and 0 or 1 on endoscopic examination) were 17% and 11% for the granulocyte/monocyte apheresis (n = 112)- and sham-treatment groups, respectively (n = 56; P = .361). Clinical response (Mayo score reduction of >/=3 points from baseline) was observed in 44% and 39% of patients, respectively (P = .620). Similar changes were observed for the apheresis- and sham-treatment groups for endoscopic remission and response, and changes in Mayo and quality-of-life scores. The companion study and pooled data from both studies also yielded similar results.

CONCLUSIONS

In this study, granulocyte/monocyte apheresis was well tolerated but did not demonstrate efficacy for induction of clinical remission or response in patients with moderate-to-severe ulcerative colitis.

Crohn's disease: beyond antagonists of tumour necrosis factor

In the past few years, antagonists of tumour necrosis factor have resulted in unforetold therapeutic benefits in Crohn's disease, but the magnitude and duration of responses are variable. New agents are therefore needed. Their development has benefited from advances in the understanding of the pathophysiology of this disease. Uncontrolled activation of the acquired immune system has an important role, and lymphocytes, cytokines, and adhesion molecules are broadly targeted for therapeutic intervention. With increasing evidence of an implication of the innate immune system and the intestinal epithelium, the therapeutic paradigm is also shifting from mere immunosuppression to the reinforcement of the intestinal barrier. We review mechanisms of actions of new drugs and the efficacy and adverse events from data from clinical trials. We discuss future directions, including new strategies with optimum endpoints.

Intensive granulocyte and monocyte adsorption versus intravenous prednisolone in patients with severe ulcerative colitis: an unblinded randomised multi-centre controlled study

BACKGROUND AND AIM

Several uncontrolled studies have reported on the efficacy of adsorptive depletion of peripheral blood granulocytes and monocytes/macrophages (GM) in patients with moderate or severe ulcerative colitis. This study was to compare the efficacy and safety of intensive GMA with intensive intravenous prednisolone in patients with severe ulcerative colitis.

METHODS

Seventy patients with clinical activity index 10-23 were randomly assigned to intensive GMA with the Adacolumn, at 2 sessions/week in the first 3 weeks and then 1 session/week for up to 11 sessions (n = 35) or intravenous prednisolone, 40-60 mg/day for 5-10 days (n = 35). No patient received immunomodulators within 8 weeks prior to entry. Clinical response based on intention to treat was assessed at weeks 2, 6 and 12.

RESULTS

Four patients in the prednisolone group and two patients in the GMA group discontinued in week 1. At weeks 2, 6 and 12, the remission (clinical activity index < or = 4) rates (%) in the GMA group were 17.1, 54.4, 74.3, respectively. The corresponding values in the prednisolone group were 25.7, 51.4 and 48.6. Further, at week 12, 27 patients (77%) in the GMA group and 5 patients (14%) in the prednisolone group were steroid free (P = 0.0076). In the GMA group, flushing and light-headedness were observed in 5 patients versus typical steroid side effects in 29 patients of the prednisolone group.

CONCLUSIONS

In this clinical response to GMA was comparable or better than prednisolone. Further, the response to GMA was slower than to intravenous prednisolone, but was more sustainable than the latter.

Selective leukocyte apheresis for the treatment of inflammatory bowel disease

The etiology of inflammatory bowel disease (IBD) is not completely understood, thus current therapies have been empirical and directed at treating symptoms rather than addressing the cause. In IBD, the overexpression of proinflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, leads to a persistent intestinal inflammatory response that damages the intestinal mucosa. Recent advances in pharmacologic therapies that target specific cytokines, chemokines, and adhesion molecules have proved successful in alleviating symptoms for some patients. There are 2 selective adsorption apheresis devices that remove leukocytes from whole blood, which are currently available in Japan and Europe-the Cellsorba leukocytapheresis column and the Adacolumn adsorptive extracorporeal granulocyte/monocyte apheresis device. The purported mechanisms of action of these devices have been extensively reviewed and are believed to exert an immunomodulatory and/or anti-inflammatory effect on patients with systemic inflammatory disease. The clinical trials presented here indicate that selective leukocyte apheresis effectively removes activated granulocytes and monocytes/macrophages from peripheral blood while maintaining an excellent safety profile. Despite these findings, large controlled trials of selective leukocyte apheresis in the treatment of IBD are needed to determine the true efficacy of this approach.

Current pharmacologic treatment paradigms for inflammatory bowel disease and the potential role of granulocyte/monocyte apheresis

BACKGROUND

A broad range of pharmacologic therapies are available to treat active inflammatory bowel disease (IBD), including 5-aminosalicylate preparations, corticosteroids, and immunosuppressants (e.g., azathio prine/6-mercaptopurine [AZA/6-MP] or methotrexate). Although these therapies are effective, up to 60% of patients are refractory or intolerant. Biologic therapies, such as the anti-TNF agent infliximab, offer promise but are not without controversy; despite many positive reports, steroid-refractory patients are less likely than other individuals to respond to infliximab. Effective, long-term therapies that do not add to the adverse-effects burden in patients with IBD are needed. Of these, granulocyte/monocyte apheresis (GMA) is one promising approach.

SCOPE

PubMed and relevant congresses databases were searched using the terms 'granulocyte/monocyte apheresis,' 'GMA,' 'leukocytapheresis,' 'Adacolumn,' and 'Cellsorba.' These studies were further selected to include only those focusing on IBD. A time frame of 2000-2006 was used.

FINDINGS

Data from open-label trials show that patients with moderate-to-severe IBD refractory to conventional pharmacologic treatment achieved clinical response and/or remission after treatment with GMA. Furthermore, recent small open-label trials of GMA show increased rates of induction and maintenance of response/remission in steroid-naïve IBD patients.

CONCLUSIONS

The remission rates seen in these open-label clinical trials of GMA are consistent with those of currently available pharmacologic therapies for IBD. However, the majority of these trials enrolled only small numbers of patients, were largely open-label, and were of limited duration. These data must be confirmed in well-controlled, large-scale clinical trials.

A novel sphingosine 1-phosphate receptor agonist, 2-amino-2-propanediol hydrochloride (KRP-203), regulates chronic colitis in interleukin-10 gene-deficient mice

Current treatments for patients with Crohn's disease (CD) are based on recent advances in elucidating the pathophysiology of the disease. A satisfactory therapeutic strategy has not been well established. A new sphingosine 1-phosphate (S1P) receptor agonist, 2-amino-2-propanediol hydrochloride (KRP-203), has been developed for immunomodulation in autoimmune diseases and organ transplantation. We aimed to evaluate the efficacy and potency of KRP-203 on the treatment of chronic colitis in an interleukin (IL)-10 gene-deficient (IL-10(-/-)) mouse model. KRP-203 agonistic activity on S1P receptor was assessed in vitro. KRP-203 was administered for 1 or 4 weeks to IL-10(-/-) mice with clinical signs of colitis. The histological appearance of the colon and the numbers, phenotype, and cytokine production of lymphocytes were compared with a control group. KRP-203 treatment was effective in preventing body weight loss in the IL-10(-/-) colitis model. One-week administration resulted in the sequestration of circulating lymphocytes within the secondary lymphoid tissues. After 4 weeks of treatment, highly significant reductions were observed in number of CD4(+) T cell and B220(+) B cell subpopulations in the lamina propria of the colon and peripheral blood. KRP-203 obviously inhibited the production of interferon-gamma, IL-12, and tumor necrosis factor-alpha by the colonic lymphocytes, but had no influence on IL-4 production. KRP-203 significantly inhibits ongoing IL-10(-/-) colitis in part through decreasing the infiltration of lymphocytes at inflammatory sites and by blocking T-helper 1 cytokine production in the colonic mucosa. Therefore, the possibility arises that KRP-203 plays a potential role in control of chronic colitis.

Novel and future medical management of inflammatory bowel disease

The treatment of inflammatory bowel disease (IBD) is undergoing rapid and profound change. Entirely new approaches are being developed that reflect a greater understanding of how to control the inflammatory process. These began with inflixumab therapy for Crohn's disease. Additional tumor necrosis antibodies will soon be employed, and other biological agents are being investigated. Probiotics, helminth ova therapy, alternative and complementary treatments, leukocytophoresis, and bone-marrow and stem-cell transplantation are additional exciting regimens that are being explored. Although some of these approaches provide marked improvement in these parameters, others are unproven or fraught with adverse effects and complications. Still, control of ulcerative colitis and Crohn's is improving with more changes likely to come.

The fundamental basis of inflammatory bowel disease

Two broad hypotheses have arisen regarding the fundamental nature of the pathogenesis of inflammatory bowel diseases (IBDs, which include ulcerative colitis and Crohn disease). The first contends that primary dysregulation of the mucosal immune system leads to excessive immunologic responses to normal microflora. The second suggests that changes in the composition of gut microflora and/or deranged epithelial barrier function elicits pathologic responses from the normal mucosal immune system. Here we examine these hypotheses and conclude that IBD is indeed characterized by an abnormal mucosal immune response but that microbial factors and epithelial cell abnormalities can facilitate this response.