Increased in vitro release of soluble interleukin 2 receptor by colonic lamina propria mononuclear cells in inflammatory bowel disease

Biological significance of soluble IL-2 receptor

A NUMBER of receptors for growth factors and differentiation antigens have been found to be secreted or released by cells. Following mononuclear cell (MNC) activation and interleukin-2 receptor (IL-2R) expression, a soluble form of the Alpha;-chain of IL-2R (sIL-2R) is released. The sIL-2R has been shown to be present in the culture supernatants of activated MNCs as well as in normal sera and, in higher amounts, in sera from subjects affected by several diseases including neoplastic, infectious and autoimmune ones, and in sera from transplanted patients suffering allograft rejection. The blood sIL-2R levels depend on the number of producing cells and the number of molecules per cell, so that sIL-2R blood values may represent an index of the number and the functional state of producing cells, both normal and neoplastic. Thus, monitoring of the immune system, mostly T-cells and haematological malignancies might be targets for the measurement of sIL-2R. Since many conditions may influence sIL-2R production, little diagnostic use may result from these measurements. However, since blood sIL-2R levels may correlate with disease progression and/or response to therapy, their measurement may be a useful index of activity and extent of disease. The precise biological role of the soluble form of the IL-2R is still a matter of debate. However, we know that increased sIL-2R levels may be observed in association with several immunological abnormalities and that sIL-2R is able to bind IL-2. It is conceivable then that in these conditions the excess sIL-2R released in vivo by activated lymphoid cells or by neoplastic cells may somehow regulate IL-2-dependent processes. On the other hand, it cannot exclude that sIL-2R is a by-product without biological significance. Finally, it is puzzling that in many conditions in which an increase of blood sIL-2R values has been observed, MNCs display a decreased in vitro capacity to produce sIL-2R. These seemingly contrasting findings are discussed in the light of the data showing that sIL-2R production correlates with IL-2 production.

Ileoanale Pouch-Operation

Restorative proctocolectomy with an ileal pouch-anal anastomosis is the treatment of choice in patients with ulcerative colitis (UC) and familial adenomatous polyposis requiring surgical therapy. Pouchitis is the most frequent complication, occurring in up to 50% of patients with underlying UC. Clinical symptoms of the disease are non-specific. Moreover, surgical complications must be differentiated from idiopathic pouchitis using pouchoscopy, endoscopic ultrasound or MRI of the pelvis in certain cases. The therapy for idiopathic pouchitis, its etiology and pathophysiology being unclear, is based on antibiotic treatment, usually with metronidazole or ciprofloxacin. Probiotics such as VSL#3 can be used to prevent relapse. In summary, the clinical and functional outcomes are excellent and stable for 20 years after surgery.

Increased cytokine transcripts in pouchitis reflect the degree of inflammation but not the underlying entity

BACKGROUND AND AIMS

After ileopouch anal anastomosis (IPAA), 10-40% of patients with ulcerative colitis (UC) but only 5% of patients with familial adenomatous polyposis (FAP) develop pouchitis. Immunoregulatory abnormalities might be of importance in the pathogenesis of the disease. Therefore, we characterized cytokine and chemokine transcripts in inflamed and non-inflamed pouches in patients with UC compared to those with FAP and Crohn's disease (CD).

PATIENTS AND METHODS

Mucosal biopsies were taken from 87 patients with IPAA [UC (n=70), CD (n=8) or FAP (n=9)]. Patients with active ileal CD (n=14), active UC (n=17) and non-inflammatory conditions (n=12) served as controls. The expression of 20 gene transcripts was quantified using real-time polymerase chain reaction.

RESULTS AND FINDINGS

Pro-inflammatory cytokines and chemokines are significantly increased in IPAA patients with acute pouchitis. This increase is independent of the underlying disease (UC or CD) and reflects the degree of inflammation. A good correlation between pouchitis activity (using the Pouchitis Disease Activity Index) and the MRP-14, interleukin-8, macrophage inflammatory protein-2alpha and matrix metalloproteinase-1 transcripts was observed.

INTERPRETATIONS AND CONCLUSIONS

Our data support the view that pouchitis reflects an inflammatory process that is different from that of underlying inflammatory bowel diseases, as the cytokine and chemokine patterns in pouchitis are neither typical of CD nor of UC, but maybe due to bacterial intestinal microflora overgrowth in the pouch lumen. Quantification of transcript levels allows an estimation of the extent of mucosal inflammation and may become helpful in the evaluation of the disease, especially in clinical trials.

IL-10 producing CD14low monocytes inhibit lymphocyte-dependent activation of intestinal epithelial cells by commensal bacteria

Intestinal epithelial cell (IEC) activation by non-pathogenic, commensal bacteria was demonstrated to require the presence of immunocompetent cells. In this study, HT-29 and CaCO-2 transwell cultures, reconstituted with CD4+ and CD8+ T cells, CD19+ B cells and CD14high monocytes, were challenged with non-pathogenic Gram negative Escherichia coli and Gram positive lactobacilli. Cytokine expression was analysed by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assays (ELISA). Expression of tumour necrosis factor alpha (TNF-alpha) and interleukin (IL)-8 mRNA in E. coli or L. sakei challenged IEC was promoted by lymphocyte populations predominantly CD4+ T cells, while monocytes failed to mediate an inflammatory cytokine response. The monocyte phenotype and function were further characterised by flow cytometry and mixed lymphocyte reaction (MLR). During the co-culture with IEC and bacterial stimulated IEC, CD14high peripheral blood monocytes acquired a CD14low CD16low phenotype with reduced expression co-stimulatory (CD80, CD86, CD58) cell surface molecules. Immunosuppressive functions of IEC conditioned CD14low monocytes were demonstrated by the predominant secretion of IL-10 and IL-IRa and their reduced potential to trigger an allogeneic lymphocyte response. In conclusion, IEC contribute to the development of CD14low CD16low monocytes with immunosuppressive function and antagonised a lymphocyte-mediated activation of the intestinal epithelium in response to intestinal and food derived bacteria. These results strengthen the hypothesis that the gut epithelium constitutes an important functional element in the regulation of mucosal immune homeostasis towards commensal bacteria.

In vitro production of TNFα, IL-6 and sIL-2R in Chinese patients with ulcerative colitis

AIM: To determine the tumor necrosis factor alpha (TNFα), interleukin 6 (IL-6) and soluble interleukin 2 receptor (sIL-2r) from peripheral blood mononuclear cells (PBMC) in 25 Chinese patients with ulcerative colitis and 20 healthy controls.

METHODS: PBMC were isolated by density gradient centrifugation of heparinized blood and cultures for 24 or 48 h by stimulation with LPS or PHA. TNFα and sIL-2r were measured by ELISA method and IL-6 measured by biossay.

RESULTS: TNFα production stimulated by LPS and sIL-2r production by PHA in ulcerative colitis were significantly lower than in healthy controls (TNFα 509 (46-7244) ng/L vs 1995 (117-18950) ng/L, P < 0.05; sIL-2r 320 U/mL ± 165 U/mL vs 451 U/mL ± 247 U/mL, P < 0.05). Spontaneous TNFα and sIL-2r production were not significantly different between ulcerative colitis and controls (TNFα 304 (46-7044) ng/L vs 215 (46-4009) ng/L, P > 0.05; sIL-2r 264 U/mL ± 115 U/mL vs 236 U/mL ± 139 U/mL, P > 0.05). IL-6 production by spontaneous release from PBMC in ulcerative colitis group was 109 U/mL ± 94 U/mL vs 44 U/mL ± 39 U/mL for those in healthy controls, P < 0.01. IL-6 stimulated by LPS in ulcerative colitis group was (261 U/mL ± 80 U/mL) higher than in healthy controls (102 U/mL ± 54 U/mL, P < 0.01). No correlation of TNFα, IL-6, sIL-2r production was found to disease activity, disease location and medication.

CONCLUSION: Cytokine production from PBMC was also disturbed in Chinese patients with ulcerative colitis.

Increased secretion of pro-inflammatory cytokines by circulating polymorphonuclear neutrophils and regulation by interleukin 10 during intestinal inflammation

BACKGROUND

Concentrations of pro-inflammatory cytokines are increased in the intestinal mucosa of patients with active inflammatory bowel disease (IBD). Polymorphonuclear neutrophil granulocytes (PMN) are the most abundant cell type in intestinal lesions in IBD. Interleukin 10 (IL-10) is an important contra-inflammatory cytokine which induces downregulation of pro-inflammatory cytokines.

AIMS

To investigate whether PMN from patients with IBD or infectious colitis, respectively, secrete increased amounts of pro-inflammatory cytokines and can be regulated by IL-10.

METHODS

Secretion (ELISA) as well as corresponding mRNA levels (semiquantitative RT-PCR) of pro-inflammatory cytokines (IL-1 beta, TNF-alpha) and of IL-1 receptor antagonist were assessed in peripheral PMN.

RESULTS

PMN from patients with IBD are primed to secrete enhanced amounts of pro-inflammatory cytokines accompanied by detection of corresponding mRNAs in comparison with normal controls. This finding is not specific for IBD but rather reflects intestinal inflammation in general. IL-10 markedly inhibited proinflammatory cytokine secretion as well as corresponding mRNA concentrations.

CONCLUSIONS

PMN are an important source of pro-inflammatory cytokines in patients with intestinal inflammation and can be downregulated by IL-10.

The circulating common gamma chain (CD132) in inflammatory bowel disease

OBJECTIVE

Inflammatory bowel disease (IBD) is characterized by T cell activation. Activated T cells shed interleukin-2 receptors (IL-2R) in a soluble form. A positive correlation between sIL-2Ralpha (CD25) and disease activity is well documented in IBD, whereas IL-2Rgamma (CD132) has not been investigated in this respect. Sera from 42 patients with ulcerative colitis (UC), 34 with Crohn's disease (CD), 31 healthy volunteers, and 12 patients with infectious enterocolitis were obtained.

METHODS

Disease activity was scored according to a semiquantitative score for UC and CD. sIL-2R alpha chain and gamma chain were assessed by sandwich ELISA techniques using monoclonal antibodies specific for CD25 and CD132, respectively.

RESULTS

The concentration of IL-2Ralpha chain (CD25) was found to be median 3.8 ng/ml in healthy volunteers versus 7.0 ng/ml in UC patients (p < 0.001), and 9.6 ng/ml in CD patients (p < 0.001). With respect to IL-2Rgamma (CD132), significantly higher amounts were found in CD patients: 6.6 ng/ml as compared with healthy controls <1.0 ng/ml (p < 0.004). A Kruskal-Wallis test revealed a significant correlation between alpha chain and disease activity in CD (p < 0.001), and further significantly higher gamma chain levels were found in active CD (p = 0.03). For UC patients, a statistically significant increase of the alpha chain with increasing disease activity (p < 0.01) was observed, whereas no significant changes of the gamma chain levels were found (p > 0.05). A difference of gamma chain levels were found between CD and UC in moderate and severe disease activity (p < 0.05). Further analyses revealed that mesalazine did not influence the IL-2Ralpha or -gamma concentration either in UC or in CD patients.

CONCLUSION

An increased circulating level of the soluble common gamma chain (CD132) seems to be found in CD, and an overlap exists between CD and UC.

Renal tubular dysfunction in patients with inflammatory bowel disease treated with aminosalicylate

BACKGROUND

An increasing number of case reports indicate potential nephrotoxicity of 5-aminosalicylic acid (5-ASA), which shares similarities with the chemical structures of both phenacetin and acetylsalicylic acid.

AIM

In a point prevalence study the occurrence of sensitive indices indicative of early kidney malfunction was assessed in outpatients with inflammatory bowel disease.

METHODS

Routine indices of kidney function (creatinine clearance, urinary protein content, pH, electrolytes, and microscopy) were investigated in 223 patients with inflammatory bowel disease as well as sensitive markers of glomerular or tubular dysfunction (microproteinuria by SDS polyacrylamide gel electrophoresis (SDS-PAGE), urinary concentrations of N-acetyl-beta-D-glucosaminidase, alpha 1-microglobulin, gamma-glutamyltransferase (GGT), alkaline phosphatase (AP), and albumin). Histories of exposure to 5-ASA were assessed by questionnaire.

RESULTS

Patients receiving high amounts of 5-ASA, both actual as well as on a lifetime basis, showed an increased prevalence of tubular proteinuria by SDS-PAGE. Raised values for urinary AP and GGT indicate proximal tubular epithelial cells as the source. All other kidney function tests were normal. Analysis of covariates indicated strong associations between disease activity and size of 5-ASA doses as well as alterations in kidney tubular function.

CONCLUSION

The possibility exists that high doses of 5-ASA may be associated with proximal tubular proteinuria. This point prevalence study cannot dissect the possible impact of chronic inflammation from high dose 5-ASA treatment and further prospective studies are warranted.

Differences in immunophenotyping of mucosal lymphocytes between ulcerative colitis and Crohn's disease

OBJECTIVES

Immunologic studies have characterized the numbers and types of inflammatory cells in diseased inflammatory bowel disease (IBD) mucosa but have yielded conflicting results regarding intestinal lymphocytes activation in IBD. We investigated the levels of lymphocytes subsets, interleukin-2 receptor, transferrin receptor, and T cell receptors in mainly isolated lamina propria lymphocytes. Including intraepithelial lymphocytes of normal colonic mucosa or IBD (ulcerative colitis and Crohn's disease) mucosa to understand the pathogenesis of IBD. We have results from this study.

RESULTS

1) In comparing ulcerative colitis with control, IL-2R (p < 0.05), TR (p < 0.01), and CD3/HLA-DR (< 0.05) showed a significant increase. 2) In comparing Crohn's disease with control, CD3 (P < 0.05), TCR alpha/beta (p < 0.01) and TCR gamma/delta (p < 0.05) showed a significant decrease. 3) In comparing Crohn's disease with ulcerative colitis, CD19 (p < 0.01), TR (p < 0.01), TCR alpha/beta (p < 0.01) and TCR gamma/delta (p < 0.05) showed a significant decrease.

CONCLUSION

From these results, there are increased T cell markers, IL-2R, TR, and CD3/HLA-DR in UC, but differently, decreased CD3, TCR alpha/beta and TCR gamma/delta in CD compared with control. In addition, definitive differences in lymphocytes markers, CD19, TR, TCR alpha/beta and TCR gamma/delta, which are higher in UC than in CD, may elucidate the different immunopathogenesis between UC and CD.

Alterations of the mucosal immune system in inflammatory bowel disease

The normal intestinal immune system is under a balance in which proinflammatory and anti-inflammatory cells and molecules are carefully regulated to promote a normal host mucosal defense capability without destruction of intestinal tissue. Once this careful regulatory balance is disturbed, nonspecific stimulation and activation can lead to increased amounts of potent destructive immunologica and inflammatory molecules being produced and released. The concept of balance and regulation of normal mucosal immune and inflammatory events is indicative of how close the intestine is to developing severe inflammation. The normal intestinal mucosal immune system is constantly stimulated by lumenal contents and bacteria. The stimulatory molecules present in the intestinal lumen that activate and induce subsequent mucosal immunologic and inflammatory events include bacterial cell wall products, such as peptidoglycans and lipopolysaccharides, as well as other chemotactic and toxic bacterial products that are produced by the many different types of bacteria within the gastrointestinal tract. These highly stimulatory bacterial cell wall products are capable of activating macrophages and T lymphocytes to release potent proinflammatory cytokines, including interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha). IL-1, IL-6, and TNF-alpha increase the presence of human leukocyte antigen (HLA) class II antigen-presenting molecules on the surfaces of epithelial cells, endothelial cells, macrophages, and B cells, thus increasing their ability to present lumenal antigens and bacterial products. The proinflammatory cytokines IL-1 and TNF-alpha also increase the ability of epithelial cells, endothelial cells, macrophages, and fibroblasts to secrete potent chemotactic cytokines, such as interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), which serve to increase the movement of macrophages and granulocytes from the circulation into the inflamed mucosa. Thus, through lumenal exposure to potent, nonspecific stimulatory bacterial products, the state of activation of the intestinal immune system and mucosal inflammatory pathways are markedly up-regulated. This raises the question of whether there is a deficiency in effective down-regulation through the absence of normally suppressive cytokines such as interleukin-10 (IL-10), transforming growth factor-beta (TGF-beta), interleukin-4 (IL-4), and IL-1 receptor antagonist. Normally, the turning off of the active and destructive immunologic and inflammatory events should occur following the resolution of a bacterial or viral infection that has been appropriately defended against and controlled by the mucosal immune system. In inflammatory bowel disease (IBD), however, the down-regulatory events and processes that should turn off the immunologic and inflammatory protective processes, once the pathogenic agent has been cleared, appear to be deficient or only partially effective. We may find that we ultimately are dealing with disease processes that have more than one genetic or cellular basis. The improved understanding of the immunopathophysiology of IBD will allow exploration of novel immunologic and genetic approaches, such as gene replacement therapy, administration of a suppressor cytokine or an altered cell surface antigen, the administration of humanized monoclonal antibodies directed against proinflammatory cytokines, or the development of newer strategies against fundamental cell biologic mechanisms such as adhesion molecules.

Immunoregulatory role of interleukin 10 in patients with inflammatory bowel disease

BACKGROUND/AIMS

Active inflammatory bowel disease (IBD) is associated with increased proinflammatory cytokines. Deficiency of interleukin (IL) 10, a contrainflammatory cytokine, leads to the development of colitis in IL-10 knockout mice. We characterized IL-10 regulation of proinflammatory cytokine (tumor necrosis factor [TNF] alpha and IL-1 beta) expression in IBD in vitro and in vivo.

METHODS

IL-10 regulation of IL-1 beta, TNF-alpha, and IL-1 receptor antagonist expression by peripheral monocytes or isolated lamina propria mononuclear cells (LPMNC), respectively, was studied by enzyme-linked immunosorbent assay (cytokine secretion) and by semiquantitative reverse-transcription polymerase chain reaction.

RESULTS

IL-10 down-regulates IL-1 beta and TNF-alpha secretion as well as messenger RNA levels in IBD peripheral monocytes and LPMNC in a dose-dependent manner. In parallel, IL-1 receptor antagonist secretion is induced, and IL-10 can restore diminished in vitro IL-1 receptor antagonist/IL-1 beta ratios in IBD to normal levels. Equal concentrations of IL-10 are detectable in both normal and IBD intestinal lamina propria biopsy homogenates. After topical IL-10 enema treatment of three steroid therapy-refractory patients with ulcerative colitis, in vitro release of proinflammatory cytokines from IBD peripheral monocytes as well as LPMNC is dramatically down-regulated.

CONCLUSIONS

IL-10 down-regulates the enhanced secretion as well as messenger RNA levels of proinflammatory cytokines by IBD mononuclear phagocytes in vitro. In vivo topical application of IL-10 induces down-regulation of proinflammatory cytokine secretion both systemically and locally.

Impaired response of activated mononuclear phagocytes to interleukin 4 in inflammatory bowel disease

BACKGROUND/AIMS

In inflammatory bowel disease (IBD), peripheral monocytes and intestinal macrophages show an increased state of priming and activation. The aim of this study was to test the hypothesis that the response of IBD mononuclear phagocytes to the contrainflammatory cytokine interleukin (IL) 4 may be altered.

METHODS

The in vitro secretion of proinflammatory cytokines (IL-1 beta, tumor necrosis factor alpha [TNF-alpha], and IL-1-receptor antagonist [IL-1ra]) by peripheral monocytes and by intestinal lamina propria mononuclear cells (LPMNCs) was assessed by enzyme-linked immunosorbent assay. In parallel, superoxide anion release, macrophage mannose receptor, and IL-4 receptor expression were investigated.

RESULTS

IBD peripheral monocytes and intestinal LPMNCs in vitro secrete increased amounts of proinflammatory cytokines (IL-1 beta and TNF-alpha) with decreased IL-1ra/IL-1 beta ratios. IL-4 down-regulates proinflammatory cytokine (IL-1 beta and TNF-alpha) and superoxide anion secretion in a dose-dependent manner. In contrast to normal and disease-specific controls, IBD peripheral monocytes and IBD intestinal LPMNCs show a diminished responsiveness to the inhibitory effect of IL-4. The IL-1ra/IL-1 beta ratios in normal monocytes are increased by IL-4, whereas in IBD monocytes low IL-1ra/IL-1 beta ratios persist after IL-4 treatment. IL-4-induced expression of macrophage mannose receptor, which is a molecule pivotal to macrophage-mediated host defense, again appeared to be impaired in IBD monocytes.

CONCLUSIONS

IL-4-mediated regulation of mononuclear phagocyte effector functions is disturbed in IBD.

Alterations in the mucosal immune system in ulcerative colitis and Crohn's disease

Emphasis is now being placed upon obtaining a better understanding of the regulatory cytokines that normally downregulate acute intestinal inflammation. These inhibitory cytokines appear to be missing or not functioning properly in patients with inflammatory bowel disease (IBD), thereby leading to perpetuation of inflammation. As we obtain an increased understanding of immune and inflammatory regulatory processes in the intestine, we will be able to devise better future therapeutic strategies for use in our IBD patients.

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.

Increased spontaneous secretion of rheumatoid factor by intestinal lamina propria mononuclear cells from Crohn's disease but not ulcerative colitis patients

Increased levels of rheumatoid factors (RF) have been observed in the serum of Crohn's disease but not ulcerative colitis patients, and have been proposed to relate to an increased state of intestinal lymphocyte activation. We have therefore examined the spontaneous in vitro secretion of RF by intestinal lamina propria mononuclear cells (MNC) isolated from specimens from control and inflammatory bowel disease (Crohn's disease, ulcerative colitis) patients. Normal intestinal lamina propria MNC spontaneously secrete rheumatoid factors of different isotypes during 14 days of in vitro culture (9.7 ng/ml IgA RF, 11.6 ng/ml IgM RF and 64.6 ng/ml IgA anti-Fc (IgG)). In matched studies intestinal MNC isolated from normal large bowel exhibited significantly greater levels of RF synthesis and secretion in vitro than normal small bowel intestinal MNC. A large increase in spontaneous RF secretion was observed from Crohn's disease intestinal MNC (21.4 ng/ml IgA RF, 21.4 ng/ml IgM RF, and 108.15 ng/ml IgA anti-Fc (IgG)), when compared with normal controls. The amount of RF secreted was dependent on the amount of inflammatory activity of the bowel specimens, from which the MNC were isolated (198.3 ng/ml of IgA anti-Fc(IgG) from involved versus 50.0 ng/ml from matched non-involved tissue). Ulcerative colitis MNC released decreased amounts of RF (7.1 ng/ml IgA RF, 6.2 ng/ml IgM RF, and 42.3 ng/ml IgA anti-Fc(IgG)). These observations using isolated intestinal MNC may explain the findings of RF changes in the sera of inflammatory bowel disease patients. Our observations support the hypothesis of a heightened state of activation in normal intestinal lamina propria MNC, which is further increased in active Crohn's disease. The dissimilarities observed between Crohn's disease and ulcerative colitis may indicate fundamental differences in disease pathophysiology and will lead to further studies exploring intestinal immunoregulatory properties of RF.

Immune activation genes in inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease is associated with enhanced activation of T cells, but the genes responsible for this state are not well characterized.

METHODS

T-cell activation genes were studied in peripheral blood and intestinal mucosal mononuclear cells of control, Crohn's disease, and ulcerative colitis patients.

RESULTS

In all groups the expression of interleukin-2 (IL-2), IL-2 receptor alpha (IL-2R alpha), and IL-2R beta messenger RNA (mRNA) was significantly higher in intestinal than circulating cells, and it correlated well with protein levels. Both IL-2R alpha and IL-2R beta mRNA were abundant in mucosal cells, suggesting that a substantial number of them displays high affinity IL-2R. This would explain why intestinal cells proliferate more, express more IL-2 transcripts, and secrete more IL-2 than peripheral cells. Inflammatory bowel disease cells produced similar or higher IL-2R alpha and IL-2R beta mRNA than controls but generated significantly lower IL-2 mRNA. Thus, the reported defect of IL-2 activity in Crohn's disease and ulcerative colitis is probably related to decreased IL-2 transcription. Crohn's disease intestinal cells had the highest expression of IL-2R gene products. This provides a mechanism for their increased response to IL-2 and supports claims that elevated soluble IL-2R alpha serum levels reflect gut T-cell hyperactivity in this disease.

CONCLUSIONS

These findings underscore the importance of T cells in mucosal immunity and indicate that abnormal T-cell activation is intimately associated to the pathogenesis of inflammatory bowel disease.

Soluble interleukin 2 and CD8 and CD4 receptors in inflammatory bowel disease

Serum levels of soluble interleukin 2 receptor (sIL-2R) have been proposed as a clinical marker of inflammatory bowel disease. The source of sIL-2R in patients with Crohn's disease and ulcerative colitis is unknown, and other soluble receptors have not been investigated. In the present study, sIL-2R and soluble CD8 and CD4 levels were measured in plasma and culture supernatants of peripheral blood and intestinal mucosal mononuclear cells from patients with inflammatory bowel disease, surgical controls, and healthy subjects. Level of plasma sIL-2R was significantly higher in patients with Crohn's disease and ulcerative colitis than in healthy volunteers. Intestinal cells always produced more sIL-2R than peripheral cells. Spontaneous sIL-2R production by mucosal cells was significantly elevated in Crohn's disease but not in ulcerative colitis supernatants compared with levels of surgical controls. Soluble CD8 and CD4 were poor indicators of systemic or mucosal immunity. A positive correlation was found between plasma sIL-2R and spontaneous production by intestinal cells of patients with Crohn's disease and surgical control patients, whereas ulcerative colitis plasma sIL-2R correlated with spontaneous production by peripheral cells. The association of plasma or spontaneous sIL-2R levels with the degree of intestinal inflammation was weak, and there was a wide overlap with control values. Therefore, caution should be used before considering sIL-2R an accurate marker of inflammatory bowel disease activity.