THE ROLE OF THE MUCOSAL IMMUNE SYSTEM IN INFLAMMATORY BOWEL DISEASE

Ulcerative colitis and adenocarcinoma of the colon in G alpha i2-deficient mice

G proteins are involved in cellular signalling and regulate a variety of biological processes including differentiation and development. We have generated mice deficient for the G protein subunit alpha i2 (G alpha i2) by homologous recombination in embryonic stem cells. G alpha i2-deficient mice display growth retardation and develop a lethal diffuse colitis with clinical and histopathological features closely resembling ulcerative colitis in humans, including the development of adenocarcinoma of the colon. Prior to clinical symptoms, the mice show profound alterations in thymocyte maturation and function. The study of these animals should provide important insights into the pathogenesis of ulcerative colitis as well as carcinogenesis.

Phenotypic and immunoregulatory analysis of intestinal T-cells in patients with inflammatory bowel disease: evaluation of an in vitro model

Although a disturbed immune response to constituents of the gut mucosa has been implicated in the pathogenesis of inflammatory bowel disease, the mechanisms are still unclear. Intestinal T-cells derived from gut biopsies were propagated in vitro as single and co-cultures under different experimental conditions prior to flow cytometry. Intestinal T-cell lines from inflamed mucosa (n = 69) showed a significant (P < 0.001) decrease in CD4+ T-cells compared to T-cells from normal (n = 49) and uninflamed (n = 29) tissue specimens. Co-culturing of inflamed and uninflamed mucosa led to a normalization of CD4+ T-cells in cultures derived from inflamed mucosa. Analysis of supernatants revealed a significantly (P < 0.001) increased secretion of IL-4 under co-culture conditions. Moreover, stimulation of cultures derived from inflamed mucosa with rIL-4 led to a significant (P < 0.001) increase in CD4+ T-cells, whereas anti-IL-4 antibodies or IFN-gamma supplementation of T-cells derived from uninflamed mucosa significantly (P < 0.001) reduced the CD4+ subset. Treatment with IFN-gamma and anti-IL-4 antibodies did not affect the phenotype of T-cells derived from inflamed mucosa. These data suggest that IL-4 might play a key role in the intestinal immune response. Furthermore, this in vitro system allows the investigation of mucosal immune mechanisms in more detail under standardized conditions.

Circulating granulocyte antibodies in first attacks of colitis

BACKGROUND

Antineutrophil cytoplasmic antibodies (ANCA) have recently been demonstrated in the sera of patients with inflammatory bowel disease (IBD).

METHODS

The presence of ANCA was studied in 107 sera obtained during 1 year from 48 patients with a first attack of IBD and in 33 such sera from 19 patients with infectious or infectious-type colitis (non-relapsing colitis (NRC)).

RESULTS

In 65% (31 of 48) of the IBD patients positive immunofluorescence reactivity against granulocytes was observed, compared with in 5% of the NRC patients. No significant difference in granulocyte reactivity was found either between patients with colonic Crohn's disease and those with ulcerative colitis or between active and inactive phases of the disease. Most of the sera showed a perinuclear immunofluorescence staining pattern (68%), in contrast to the classical cytoplasmic staining pattern seen in Wegener's granulomatosis. In sera obtained at the first visit from the 31 IBD patients with positive granulocyte reactivity a hitherto unknown antibody against beta-glucuronidase was found in 42%, whereas in 45% the specificity was not identified. Other antibodies, rarely seen, were directed against myeloperoxidase, lactoferrin, elastase, and cathepsin G. No antibody directed against lysozyme was detected.

CONCLUSIONS

Positive granulocyte reactivity practically excluded NRC and was seen in more than half of IBD patients. Antibodies against beta-glucuronidase were common, but still almost half of the antibodies remained unknown.

Tolerability of interferon alpha-2b, a possible new treatment of active Crohn's disease

BACKGROUND AND AIMS

Due to the need for new principles for the treatment of Crohn's disease and due to the documented immunomodulatory effects of interferon alpha, the tolerability and effect(s) of interferon alpha-2b (Introna) in active Crohn's disease were examined in a pilot study.

METHODS

Five patients with active Crohn's disease (activity index (CDAI) scores of 235-517), were treated with interferon alpha-2b for 12 weeks.

RESULTS

All patients tolerated the treatment, but developed influenza-like symptoms, which were fully controlled by paracetamol. Two patients obtained partial remission with a decline in activity index scores of 39% and 50%. The activity of 2',5'-oligoadenylate synthetase, which together with two other interferon-induced proteins, neopterin and beta 2-microglobulin were increased during treatment, indicated clearly an in vivo uptake of interferon. Sedimentation rate, C-reactive protein, orosomucoid, albumin, specific inflammatory markers: soluble interleukin-2 alpha-receptors (sIL-2R) and intercellular adhesion molecule-1 (ICAM-1) did not show any changes before or after treatment.

CONCLUSION

Future multicentre investigations are required to evaluate the clinical effect of interferon alpha-2b treatment in active Crohn's disease.

Depressed T cell reactivity to recall antigens in Crohn's disease before and after surgical resection

Earlier studies regarding possible primary immune disturbances participating in the pathogenesis of Crohn's disease yielded conflicting results. Peripheral blood lymphocyte subsets and lymphocyte proliferative responses to five soluble recall antigens and to the polyclonal stimulator phythaemagglutinin were therefore measured in 17 patients with active Crohn's disease, before and six months after surgical resection of the inflamed intestine and in 16 healthy controls. Lymphocyte proliferation in response to all five recall antigens was significantly lower in patients than in controls. No significant differences with controls were detected after surgery. Addition of indomethacin to phythaemagglutinin stimulated lymphocyte cultures had a stronger proliferation enhancing effect in patients than in controls, resulting in comparable proliferative responses in both groups. When both indomethacin and prostaglandin E2 were added, inhibition of reactivity by prostaglandin E2 was stronger in patients' cultures. This suggests a higher sensitivity to inflammatory prostaglandins in Crohn's disease. The degree of lymphocyte stimulation by antigens correlated positively with the percentage of circulating memory T cells (CD 45 RA-). The percentage of activated (HLA-DR+) CD8 cells was higher in patients than in controls. The CD4/CD8 ratio, which was not significantly different between patients and controls, correlated significantly with disease activity and characteristics, even in the postoperative phase. These findings suggest that immune abnormalities in Crohn's disease fluctuate with and are probably secondary to inflammatory activity.

Evolving concepts of psychopathology in inflammatory bowel disease. Implications for treatment

The role of psychiatric factors in inflammatory bowel disease has been increasingly relegated, according to Aronowitz and Spiro, to "patient's illness, but not to disease, to therapy, but not to etiology, to symptoms, but not to pathology, and finally to the course of the disease, but not to its cause." This is not surprising in view of the fact that to attribute psychological factors to an illness is seen by the patient and physician alike as an attempt to "blame the victim." As a result, there has been a concerted effort in the past two decades in the field to replace the seemingly archaic, developmental, romantic psychoanalytic concepts of causation with more "enlightened," "scientific" paradigms of psychoneuroimmunology and psychiatric comorbidity. Despite major advances in the biomedical understanding of inflammatory bowel disease and its treatment, however, the essential questions about the complex relationship between emotional and physical symptoms remain a source of frustration both to the patient and to the treating physician in the management of the chronic diseases of the bowel. Thus, early assumptions of a psychogenic basis of ulcerative colitis and Crohn's disease may have been imprecise, but the genuine contributions of investigators such as Alexander, Karush, and Engels ought not to be cast aside completely. Experience with the treatment of patients with inflammatory bowel disease shows that attention to psychiatric comorbidity, quality of adaptation to illness, and the patient-physician relationship are essential components of a comprehensive, successful approach to these chronic illnesses.

Immunomodulator therapy in inflammatory bowel disease

The introduction of immunomodulator therapy in the treatment of patients with inflammatory bowel disease (IBD) has provided an important tool in modifying the mucosal immune system thought to be important in the pathogenesis of IBD. Currently available immunomodulating agents include azathioprine, 6-mercaptopurine, cyclosporin, and methotrexate. Recent clinical trials have demonstrated that these agents have an important therapeutic role in the treatment of patients who are either refractory or intolerant to traditional medical therapy. They are useful in the induction and maintenance of remission for both ulcerative colitis and Crohn's disease. However, these agents have significant toxicities and limited efficacy. In addition, potential risks of malignancy and infection limit their indiscriminate use. Thus, with the better understanding of the molecular basis of mucosal immunity, innovative immune-modifying therapies, such as antagonists of cytokines and inhibitors of T-cell activation, are being developed. It is likely that these exciting developments will soon result in specific immune modulating therapy with improved efficacy and reduced toxicity in the treatment of patients with IBD.

Oral 4-aminosalicylic acid versus 5-aminosalicylic acid slow release tablets. Double blind, controlled pilot study in the maintenance treatment of Crohn's ileocolitis

4-Aminosalicylic acid (4-ASA) has been suggested as an effective treatment for both active and quiescent ulcerative colitis. 5-Aminosalicylic acid (5-ASA) is well accepted for the maintenance treatment of inactive ulcerative colitis. Moreover, recent studies suggest that 5-ASA may also be effective in maintaining remission in Crohn's colitis. As treatment with 4-ASA may result in less side effects, the efficacy of a one year's maintenance treatment with oral 4-ASA (1.5 g/d, slow release tablets, n = 19) and oral 5-ASA (1.5 g/d, slow release tablets, n = 21) was compared in a double blind, randomised trial in patients with quiescent Crohn's ileocolitis. Patients with ileocolonic or colonic involvement were enrolled if in stable remission for more than two months but less than one year. Baseline demography and clinical severity were similar in both groups. Total colonoscopy and ileoscopy were performed at enrollment and at the end of the study. After one year seven of 19 patients receiving 4-ASA (36%) and 8 of 21 receiving 5-ASA (38%) had developed a clinical relapse, as defined by a rise in the Crohn's disease activity index (CDAI) of more than 100 points to values higher than 150. The relapse rates between the 4-ASA and the 5-ASA groups were not statistically different although no comparison with the spontaneous relapse rate in a placebo group could be made. Clinical relapse was accompanied by a statistically significant rise in serum concentrations of soluble interleukin 2 receptor and by an increased percentage of activated peripheral blood T cells. There were no statistical differences between the 4-ASA and the 5-ASA groups regarding the height of rise in CDAI or of soluble interleukin 2 receptor concentrations during relapse, thus showing a similar severity relapsed disease activity. In conclusion, 4-ASA maybe as effective as 5-ASA in the maintenance treatment of quiescent Crohn's disease and there were no differences in the severity of relapse between both treatment groups.

Immunoepidemiology of intestinal helminthic infections. 3. Mucosal macrophages and cytokine production in the colon of children with Trichuris trichiura dysentery

Mucosal macrophages and accessory cells have been studied by immunohistochemistry in the lamina propria of the colon of children with Trichuris trichiura dysentery syndrome (TDS). No difference was found in the numbers of cells recognized by the monoclonal antibodies CD11c, CD68, or RFD7 between TDS children and local controls. However, large numbers of cells were recognized by an antibody against calprotectin (an anti-bacterial glycoprotein found in tissue infiltrating-monocytes) in TDS colonic mucosa, but few in control colon. Large numbers of cells containing tumour necrosis factor alpha (TNF alpha) were also seen in TDS mucosa; cells isolated from TDS mucosa secreted more TNF alpha than cells from control mucosa; and children with TDS had high levels of circulating TNF alpha. Non-specific macrophage-mediated inflammation and local cytokine production may therefore play a role in the pathogenesis of TDS.

Aetiology and pathogenesis of chronic inflammatory bowel disease

While Crohn's disease and ulcerative colitis are both conditions characterized by intestinal inflammation, with some overlap in their clinical and histological features, they are essentially different in pathogenesis. Crohn's disease appears to be primarily a condition of chronic T-lymphocyte activation, with tissue damage induced by secondary macrophage activation. What activates the T-cells is unknown. In this chapter we look at the evidence for and against cell-wall deficient mycobacteria species, viral infection of vascular endothelium and luminal contents as potential mechanisms of chronic activation. In ulcerative colitis, by contrast, there is no strong evidence for T-cell activation, and humoral mechanisms predominate. While the finding of atypical anti-neutrophil cytoplasmic antibodies (P-ANCAs) may be useful in screening, the only novel pathogenetic discovery is the co-localization of a 40 kD colonic autoantibody with immunoglobulins and complement on the apical enterocyte surface. Despite the fundamental differences in initiating mechanisms, the two conditions have many 'downstream' inflammatory processes in common. We discuss the evidence for local production of cytokines, arachidonic acid metabolites and reactive oxygen and nitrogen radicals, highlighting the potential adverse consequences for intestinal vascular integrity.

Diarrhoeal disease: current concepts and future challenges. Intestinal cytokines in inflammatory bowel disease and invasive diarrhoea

In the intestine large numbers of bacteria and their products are separated by a single epithelial layer from resident inflammatory cells (macrophages and lymphocytes). Many of these bacterial products, such as lipopolysaccharides and peptidoglycans, are potent stimulators of free radical and inflammatory cytokine production by macrophages. This can occur in vivo in response to mucosal invasion by enteropathogenic bacteria or because of inappropriate activation of these cells, as in chronic inflammatory bowel disease. In this review we present evidence for production of cytokines in normal intestine and in intestinal inflammatory conditions. The adverse effects of cytokine production upon intestinal homeostasis, in particular disruption of epithelial integrity and prothrombotic changes in the vascular endothelium, are also discussed.

Interleukin-2 activity of colonic lamina propria mononuclear cells in a rat model of experimental colitis

BACKGROUND

Altered interleukin 2 (IL-2) production has been implicated in the pathogenesis of inflammatory bowel diseases.

METHODS

The temporal relationship between IL-2, prostaglandin E2 (PGE2) production, and mucosal injury was evaluated by isolated colonic lamina propria mononuclear cells (LPMC), using the trinitrobenzene sulfonic acid model of rat colitis.

RESULTS

Spontaneous LPMC IL-2 activity was significantly increased in chronic (5 weeks) but not acute (5 days) or resolved colitis groups. IL-2 activity after concanavalin A activation was highest in the groups with resolved and chronic colitis. PGE2 production was significantly increased in LPMC cultures in acute or chronic colitis as well as the ethanol control groups but not the resolved colitis group. The addition of indomethacin to LPMC cultures decreased PGE2 levels in all groups, whereas IL-2 activity increased only for the chronic and resolved colitis groups. No correlation was found between PGE2 and IL-2 production by LPMC.

CONCLUSIONS

In this experimental model, LPMC IL-2 production varied according to the severity and duration of the inflammation. Increased PGE2 production does not appear to be responsible for the IL-2 alterations in colitis.

Ulcerative colitis and total alopecia in a mother and her son

Extraintestinal autoimmune disorders are associated with ulcerative colitis in selected patients and lend support to the theory of immune-mediated injury in inflammatory bowel disease. Rarely, alopecia areata has been associated with ulcerative colitis, and familial aggregation and an HLA association have been reported for both disorders. The occurrence of both alopecia and ulcerative colitis in a mother and son are reported with a detailed investigation of antineutrophil cytoplasmic antibodies and HLA alleles in this family. Treatment with the immunosuppressive agent cyclosporine proved beneficial in the child leading to remission of the ulcerative colitis and nascent growth of scalp and body hair.