Interleukin-1 signaling is essential for host defense during murine pulmonary tuberculosis.

Interleukin (IL)-1 signaling is required for the containment of infections with intracellular microorganisms, such as Listeria monocytogenes and Leishmania major. To determine the role of IL-1 in the host response to tuberculosis, we infected IL-1 type I receptor-deficient (IL-1R(-/-)) mice, in which IL-1 does not exert effects, with Mycobacterium tuberculosis. IL-1R(-/-) mice were more susceptible to pulmonary tuberculosis, as reflected by an increased mortality and an enhanced mycobacterial outgrowth in lungs and distant organs, which was associated with defective granuloma formation, containing fewer macrophages and fewer lymphocytes, whereas granulocytes were abundant. Lymphocytes were predominantly confined to perivascular areas, suggesting a defective migration of cells into inflamed tissue in the absence of IL-1 signaling. Impaired host defense in IL-1R(-/-) mice was further characterized by a decrease in the ability of splenocytes to produce interferon-gamma. Analysis of these data suggests that IL-1 plays an important role in the immune response to M. tuberculosis.

Hapten-induced colitis associated with maintained Th1 and inflammatory responses in IFN-gamma receptor-deficient mice.

IFN-gamma is a potent pro-inflammatory cytokine thought to be involved in the pathogenesis of Crohn's disease. To further define the role of IFN-gamma in intestinal inflammation, we studied the effects of intra-colonic 2,4,6-trinitrobenzene sulfonic acid (TNBS) instillation in mice with a functionally inactivated IFN-gamma receptor 1 (IFN-gammaR1(- / -)). Our results indicate that IFN-gamma is not necessary for the induction of hapten-induced colitis: after TNBS administration both wild-type and IFN-gammaR1(- / -) mice lost body weight, and the histological features of TNBS-induced colitis were comparable. Colons of IFN-gammaR1(- / -) mice contained a greater number of cells, represented by macrophages and CD4(+) T cells; caudal lymph node cells produced more IFN-gamma and TNF-alpha upon stimulation in vitro. Moreover, IL-18 and IL-12 p40 RNA levels were comparably up-regulated after TNBS treatment in IFN-gammaR1(- / -) wild-type mice. These findings demonstrate that IFN-gamma is dispensable for the development of TNBS-induced colitis. Importantly, the production of Th1 cytokines (e. g. IFN-gamma and TNF-alpha) by caudal lymph node T lymphocytes was enhanced rather than decreased in IFNgammaR1(- / -) mice with no evidence for default Th2 development.

Does ursodeoxycholic acid mediate immunomodulatory and anti-inflammatory effects in patients with primary sclerosing cholangitis?

BACKGROUND AND OBJECTIVES: Therapy with ursodeoxycholic acid (UDCA) has been reported to be associated with improvements in abnormal serum biochemical liver tests in patients with primary sclerosing cholangitis (PSC). To evaluate further the effects of UDCA on this disease, we evaluated immunological markers and indices of inflammation during a one-year, prospective, open-label trial of UDCA therapy in patients with PSC. PATIENTS AND METHODS: Seventeen PSC patients were enrolled for one year of treatment with UDCA 12-15 mg/kg/day. Serum biochemical variables, immunological markers and indices of inflammation were compared before and at the end of therapy and 4 months after treatment had been withdrawn. Liver histology and immunohistochemistry for human leucocyte antigen (HLA) class I/II and intercellular adhesion molecule 1 (ICAM-1) expression were compared before and at the end of therapy. RESULTS: UDCA treatment was associated with significant improvements in serum biochemical liver tests, immunoglobulin levels and blood coagulation factors. Tumour necrosis factor alpha (TNF-alpha) production after in vitro whole-blood phytohaemagglutinin (PHA) stimulation was increased, but unaltered by UDCA therapy. Baseline serum levels of interleukin-6 (IL-6) and soluble IL-2 receptor were normal, and serum IL-8 levels were increased, but none of these variables was significantly affected by UDCA therapy. Liver histological stage/grade and HLA class I/II and ICAM-1 expression on biliary epithelial cells and hepatocytes were not markedly altered by UDCA therapy. CONCLUSIONS: UDCA therapy in PSC patients was associated with a decrease in cholestasis, but no consistent improvement in hepatic inflammation, fibrosis or histological stage of the disease. Immunomodulatory effects of UDCA in PSC do not appear to be HLA-restricted.

Altered expression of interferon-gamma and interleukin-4 in inflammatory bowel disease.

Experimental data indicate that mucosal CD4+ T cells play an important role in the pathogenesis of inflammatory bowel disease (IBD). Based on the pattern of cytokine production, CD4+ T cells may be distinguished into two different phenotypes. Th1 responses are characterized by secretion of interleukin (IL)-2, tumor necrosis factor (TNF)-alpha, lymphotoxin, and interferon (IFN)-gamma and are associated with delayed-type hypersensitivity reactions, whereas Th2 responses, which are characterized by secretion of IL-4, IL-5, and IL-10, have been associated with humoral immune responses and allergy. To assess the number of IFN-alpha and IL-4 positive cells in IBD and normal intestinal specimens, frozen sections from intestinal specimens from 10 Crohn's disease (CD), 8 ulcerative colitis (UC), and 8 healthy controls were examined by immunohistochemistry. Monoclonal antibodies for CD3, CD8, IFN-gamma, and IL-4 were used. T-lymphocyte infiltration and cytokine expression by epithelial, lamina propria, and submucosal cells were scored on a four-point scale by two independent observers who were blinded for the clinical data. One-way analysis of variance (ANOVA) testing was used for statistical analysis. In intestinal specimens from IBD patients, the number of CD3+ cells was found increased in the lamina propria and, within the submucosa, this increase was significant (p < 0.001). In CD the number of lamina propria IFN-gamma positive cells was significantly increased as compared with controls (p < 0.002). In UC the number of both IFN-gamma and IL-4 producing cells in the lamina propria was not significantly increased as compared with controls. The present results confirm the existence of a Th1-biased pattern production in CD but not in UC.

Immunotherapy of Crohn's disease.

Although the initiating events of Crohn's disease are unknown, models of experimental colitis have provided new insights in the immunologically mediated pathways of mucosal inflammation. In Crohn's disease activated mucosal T lymphocytes produce proinflammatory cytokines within the mucosal compartment. With this understanding, there has been a shift in past years from the use of unspecific anti-inflammatory agents (corticosteroids, aminosalicylates) to the use of immunomodulatory drugs (azathioprine, methotrexate). Moreover, novel strategies have been designed for specific targets in Crohn's disease, in particular T lymphocytes and cytokines. In an open label study treatment of steroid-refractory Crohn's disease with anti- CD4+ antibodies was well tolerated and showed clinical benefit. However, a sustained depletion of the CD4+ cells precluded further clinical trials. In controlled clinical studies, anti-tumour necrosis factor (TNF-alpha) antibodies induced complete remissions and few side effects were observed. One study suggested efficacy in active Crohn's disease of recombinant interleukin-10. Long term treatment studies will have to answer questions about the indications for use, benefit and toxicity. Altogether, these results hold promise for future management of Crohn's disease, where disease-modifying interventions and strategies that effectively maintain disease remission will play a key role.

Attenuation of proinflammatory response by recombinant human IL-10 in human endotoxemia: effect of timing of recombinant human IL-10 administration.

To determine the effects of IL-10 on cytokine and granulocyte responses during endotoxemia, two groups of eight healthy male volunteers were challenged with endotoxin (4 ng/kg) on two occasions, once in combination with placebo injection, and once in conjunction with i.v. administered recombinant human IL-10 (rhIL-10) (25 microg/kg). In group 1, rhIL-10 was administered 2 min before endotoxin challenge; in group 2, the intervention was delayed for 1 h after endotoxin administration. rhIL-10 pretreatment reduced the LPS-induced rises in temperature and release of TNF, IL-6, IL-8, and IL-1 receptor antagonist. Endotoxin-induced granulocyte accumulation in lungs, as determined by dynamic granuloscintigrams, was prevented by rhIL-10 pretreatment, whereas granulocyte recruitment in liver and spleen was only modestly reduced. In addition, granulocyte degranulation, as measured by plasma elastase/alpha1-antitrypsin complexes, was blunted significantly by rhIL-10 pretreatment. Post-treatment with rhIL-10 did not influence LPS-induced temperature responses, cytokine release, or granulocyte degranulation. Both rhIL-10 pretreatment and post-treatment reduced LPS-induced cortisol levels. These results indicate that pretreatment with rhIL-10 reduces endotoxin-induced febrile responses, cytokine responses, and granulocyte accumulation in lungs, while in this acute model post-treatment with rhIL-10 exerts limited anti-inflammatory effects.

Monoclonal antibody therapy of inflammatory bowel disease.

Animal models of inflammatory bowel disease have provided insight in the regulation of mucosal inflammation. This has resulted in novel therapeutic approaches that specifically target a single inflammatory mediator. Monoclonal antibody therapy has been used in steroid refractory Crohn's disease patients. Anti-TNF antibody administration induced complete remissions and few side effects were observed. Although these findings need to be confirmed in controlled and long term treatment studies they may guide the development of specific and effective therapies for these diseases.

Monoclonal antibody therapy of inflammatory bowel disease.

Several anti-inflammatory drugs have therapeutic efficacy in inflammatory bowel disease, but their targets remain incompletely characterized. The development of monoclonal antibodies that either recognize epitopes on immune-competent cells, or neutralize pro-inflammatory cytokines, has helped to define the importance of inflammatory mediators and their cellular sources in experimental inflammatory bowel disease. Moreover, two monoclonal antibodies, directed against CD4 and tumour necrosis factor, have been used to treat patients with steroid-refractory Crohn's disease. Preliminary data suggest that immune-modulatory monoclonal antibodies may have beneficial effects in selected patients with severe Crohn's disease.

Tumor necrosis factor (TNF) in inflammatory bowel disease: gene polymorphisms, animal models, and potential for anti-TNF therapy.

The inflammatory bowel diseases frequently require surgery because of intestinal complications. Animal models of inflammatory bowel disease, in particular those that histopathologically resemble Crohn's disease, are characterized by increased mucosal TNF production, and anti-TNF antibodies have shown efficacy in decreasing disease activity. These data have provided a rationale for immunotheraphy of Crohn's disease. Administration of anti-TNF antibodies to patients with Crohn's disease not responding to standard immunosuppressive treatment rapidly induced complete remissions, and healing of intestinal ulceration. A rapid reduction of circulating IL-6, CPR, and sPLA2 levels was observed in all patients, as well as a reduction of mucosal cells expressing RANTES and MIP-1. Short-term treatment with anti-TNF antibodies was not associated with significant toxicity, but results from long-term administration are still lacking. These data indicate that TNF is a pivotal and central inflammatory mediator in this disease. Further characterization of the precise mechanism of action of anti-TNF antibody therapy may further unravel the cause of immune dysregulation in Crohn's disease.