Differences in cytokine production by peripheral blood mononuclear cells (PBMC) between patients with atopic dermatitis and bronchial asthma.

It is widely accepted that type 2 helper T (Th2) lymphocytes play a crucial role in the pathogenesis of atopic dermatitis (AD) as well as bronchial asthma (BA). We measured the amounts of IL-5 and interferon-gamma (IFN-gamma) produced by PBMC upon stimulation with house dust mite (HDM) or Candida albicans (CA) in 17 children (3-15 years) with AD, and compared these values with those of 16 children with BA. Although IL-5 production by PBMC upon stimulation with HDM in patients with AD was significantly higher than that in 13 non-atopic controls (geometric mean = 23.4 pg/ml versus 5.9 pg/ml, P < 0.05), it was significantly lower than that in patients with BA (177.8 pg/ml, P < 0.001). The amount of IL-5 produced by PBMC upon stimulation with CA was also significantly lower in patients with AD than in those with BA (7.2 pg/ml versus 100.0 pg/ml, P < 0.001). The production of IFN-gamma by PBMC stimulated with HDM or CA was also significantly lower in patients with AD than in those with BA (HDM 4. 3 pg/ml versus 12.6 pg/ml, P < 0.05; CA 6.5 pg/ml versus 60.3 pg/ml, P < 0.001). Consequently the ratio of IL-5 to IFN-gamma production was high not only in patients with BA but also in those with AD. These findings suggest that there are some differences in the regulation of in vivo cytokine production between patients with AD and those with BA, although a Th2-dominant profile is common to both.     

Influence of atopic heredity on IL-4-, IL-12- and IFN-gamma-producing cells in in vitro activated cord blood mononuclear cells.

Several reports have claimed that there is a greater risk for a child with an atopic mother to develop allergy as compared to a child with an atopic father. This suggests that the fetal environment during pregnancy might be of importance for the development of atopic disease. Both proliferative and cytokine responses have been detected in cord blood mononuclear cells (CBMC) after stimulation with allergens, suggesting allergen priming already in utero. The aim of this study was to investigate whether the atopic status of the mother influences cytokine production by CBMC. We compared interleukin (IL)-4, IL-12 and interferon (IFN)-gamma-producing CBMC from children with double atopic heredity (dh), maternal atopic heredity only (mh) or no atopic heredity (nh). CBMC were stimulated in vitro with allergens (birch, ovalbumin and cat), phytohaemagglutinin (PHA) or purified protein derivative (PPD) and cytokine-producing cells were measured by the enzyme-linked immunospot assay. In response to PHA, the frequency of IL-4-producing cells, as well as the ratio of IL-4/IFN-gamma-producing cells, were significantly higher in the dh group compared to the nh group. High numbers of IL-12-producing cells in response to allergens were detected, significantly highest in the nh group, followed by the dh and mh groups. Our results suggest that there is a stronger Th2 bias after in vitro stimulation of CBMC from children with atopic heredity, as reflected by higher IL-4/IFN-gamma ratios in response to PHA, and lower numbers of IL-12-producing cells after allergen stimulation. Whether these differences influence later allergy development will be evaluated when the atopic status of the children is assessed at 2 years of age.     

Plasma separation in patients with bronchial asthma, atopic dermatitis and hyperimmunoglobulinaemia E

The effect of intensive plasma separation performed eight times within 5 weeks in four patients with atopic dermatitis, bronchial asthma and hyperimmunoglobulinaemia E was followed as regards clinical symptoms and changes in the concentrations of serum (S) IgE, S IgG, S IgA, S IgM, plasma complement C3 split products, S transferrin, blood eosinophils, chemotaxis of neutrophil cells and histamine metabolites in urine in samples obtained consecutively during the period of observation. The occurrence of circulating immune complexes (IC) was analysed by a polyclonal rheumatoid factor (pRF) agglutination inhibition assay and an IgE IC specific technique. IgE IC were demonstrated in three of the patients prior to plasma separation, complexed IgE was 2-3% of the total concentration of S IgE. In one patient complexes were detected by the pRF agglutination inhibition assay, also. In the three patients with IgE IC, the complexes disappeared during treatment, but recurred in two of the patients shortly after the last plasma separation. Shortly after eight separations the S IgE was reduced in all patients to a mean level of 46% of the pre-exchange concentrations. During the following 3 weeks the relative increase of S IgE in three of the patients was similar to the values obtained for S IgG. Serum IgG was subnormal in all patients during the period of treatment. Increasing numbers of eosinophils were observed in three of the patients after the fifth separation procedure. The histamine metabolite 1,4-methylimidazoleacetic (1,4- MIAA ) in urine was increased in all patients, but no significant changes were observed during the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interferon-gamma secretion of peripheral blood CD8+ T lymphocytes in patients with bronchial asthma: in vitro stimulus determines cytokine production.

It has been postulated that T lymphocytes orchestrate the chronic inflammation in bronchial asthma. In animal models, infiltration of CD8+ T lymphocytes into the bronchial mucosa prevented bronchial hyperresponsiveness and decreased early and late phase reaction. IFN-gamma antagonizes IL-4-dependent IgE production as well as IL-5-induced proliferation and activation of eosinophils. We therefore investigated the secretion of IFN-gamma of isolated CD8+ T lymphocytes from peripheral blood of patients with allergic asthma (n = 6) and from healthy controls (n = 7) in vitro. In this setting we compared the effect of stimulation with anti-CD3 antibodies with that of phorbol myristate acetate (PMA) and calcium-ionophore. As expected, CD8+ T lymphocytes from peripheral blood of healthy volunteers produced significantly more IFN-gamma in the presence of PMA and calcium-ionophore than after stimulation with anti-CD3 antibodies. However, in subjects with allergic asthma, IFN-gamma secretion of CD8+ T cells was significantly higher when incubated with anti-CD3 antibodies than after activation with PMA and calcium-ionophore. While IFN-gamma secretion of CD8+ T lymphocytes of patients with allergic asthma was lower than that of healthy controls in the presence of PMA/calcium-ionophore, it was significantly elevated when compared with normal controls after stimulation with anti-CD3 antibodies. Thus, potent activators of cytokine secretion, such as PMA and calcium-ionophore, induce a cytokine profile different from that induced by weaker stimulants, such as anti-CD3 antibodies. These findings have implications for further studies investigating cytokine production of inflammatory cells in vitro.     

Prevalence and severity of allergic rhinitis in house dust mite-allergic patients with bronchial asthma or atopic dermatitis

BACKGROUND: Allergic rhinitis, asthma and atopic dermatitis are closely associated. Although population-based studies report a high prevalence of rhinitis among asthma patients, less is known of the association between rhinitis and atopic dermatitis and the severity of concomitant rhinitis. OBJECTIVES: We aimed to determine the prevalence and severity of allergic rhinitis among asthmatics and patients with atopic dermatitis and assessed whether age and comorbidity influence the severity of rhinitis signs and symptoms. METHODS: Three hundred and twenty-five patients recruited for a multicentre trial to study the effect of encasings of mattresses, pillows and duvets on signs and symptoms of allergic rhinitis and/or asthma and/or atopic dermatitis recorded visual analogue scores (VAS) and daily symptom scores and underwent nasal challenge tests with house dust mite (HDM). RESULTS: Based on history and clinical symptoms 92% of the 164 asthmatic patients and 85% of the 86 patients with atopic dermatitis could be diagnosed as having rhinitis. Inclusion of a positive provocation to HDM did not result in a substantial lower prevalence of rhinitis. Subjects reported moderate symptoms, with mean rhinitis VAS scores ranging from 40.0 to 55.0. Presence of atopic dermatitis was associated with lower rhinitis VAS and symptoms scores, whereas in multivariate analysis the presence of asthma was positively associated with nasal responsiveness to HDM. CONCLUSION: The prevalence of nasal symptoms in patients with bronchial asthma or atopic dermatitis and sensitized to house dust mites is high. Although the majority of patients experience mild to moderate symptoms, the presence of nasal disease needs to be examined in all patients with atopic disorders.     

Mechanism of NK cell activation induced by coculture with dendritic cells derived from peripheral blood monocytes.

Dendritic cells (DCs) have been regarded as one of the effective antigen-presenting cells, but the relationship between DCs and lymphocytes, in particular natural killer (NK) cells, remains unclear. In this study, we evaluated how DCs interact with both lymphocytes and NK cells using a coculture system. The number of lymphocytes increased significantly when cocultured with DCs (1.8-fold increase). In particular, the proliferation of NK cells was prominent. Furthermore, the coculture of DCs with lymphocytes induced a marked increase in IL-12 and IFN-gamma secretion. When contact between the DCs and lymphocytes was prevented, the secretion of both IL-12 and IFN-gamma was markedly reduced. IFN-gamma production was completely blocked by an anti-IL-12 antibody, indicating that IFN-gamma secretion was dependent on IL-12 secretion. The stimulating effect of the DCs on the proliferation of the lymphocytes was partially suppressed by anti-IL-12 antibodies, and was completely attenuated when cellular contact was prevented. Furthermore, the NK cell proliferation induced by coculture with DCs was significantly blocked by the inhibition of the interaction of either CD40-CD40L or CD28-B7 molecule. The coculture with DCs enhanced NK activity by 40%, and this was partially suppressed by anti-IL-12 antibodies and was completely blocked by the inhibition of cell-to-cell contact. These results indicate that the activation of NK cells by DCs is partially mediated by IL-12 secretion, and that direct contact between DCs and NK cells play a major role in this response.     

Ribavirin inhibits DNA,RNA, and protein synthesis in PHA-stimulated human peripheral blood mononuclear cells: possible explanation for therapeutic efficacy in patients with chronic HCV infection

The treatment of choice for patients infected chronically with HCV is the combination of IFN-alpha and ribavirin. Monotherapy with ribavirin leads to a clinical and histological improvement, but its exact mechanism of action is unknown. Therefore, the effect of ribavirin on synthesis of inflammatory cytokines and on apoptosis in stimulated peripheral blood mononuclear cells (PBMCs) was investigated. PBMCs were isolated from the blood of HCV infected patients and from healthy volunteers. The effect of ribavirin on IFN-gamma and IL-1beta release in the supernatant of unstimulated and phytohemagglutinin (PHA) stimulated PBMCs was investigated by enzyme linked immunosorbent assay (ELISA). The effect on total DNA, RNA, and protein synthesis was analyzed by measurement of 3H-thymidine, 3H-uridine and 3H-leucine incorporation into cellular macromolecules. Ribavirin led to a dose-dependent decrease of the IFN-gamma but an increase of IL-1beta release into the supernatant of PHA-stimulated PBMCs. At the same time, a dose-dependent decrease of total DNA, RNA, and protein synthesis in cultures of PHA-stimulated PBMCs was demonstrated. These effects could be compensated by the addition of equimolar amounts of guanosine. The rate of apoptotic CD45+ and CD14+ cells in PBMCs cultures increased in a dose-dependent manner. Our data suggest that ribavirin administration to chronically HCV-infected patients could lead to a decrease of the synthesis of proinflammatory cytokines (e.g., IFN-gamma) by an inhibition of total DNA-, RNA-, and protein-synthesis and by induction of apoptosis in the cells of the inflammatory infiltrate. Furthermore, ribavirin could influence the synthesis of viral particles in the hepatocytes.     

In vitro responsiveness to IL-18 in combination with IL-12 or IL-2 by PBMC from patients with bronchial asthma and atopic dermatitis

Interleukin (IL)-18 is a proinflammatory cytokine and is now recognized as an important regulator of both helper T cells (Th) 1 and 2 cytokine production. An increased IL-18 secretion has been reported in patients with allergic disorders. It is predominantly produced by activated macrophages, and synergizes with IL-12 and IL-2 to induce IFN-gamma synthesis, thereby promoting Th1 cytokine response. Paradoxically, IL-18, by itself, strongly induces immunoglobulin (Ig) E and allergic inflammation, indicating a role for IL-18 in promoting Th2 response. We investigated the inducing effect in vitro of combining IL-18 and Il-12 or Il-2 on Th1- and Th2-type cytokines production by peripheral blood mononuclear cells (PBMC) from patients with allergic diseases. PBMC derived from 44 allergic patients [23 bronchial asthma (BA) and 21 atopic dermatitis (AD)] and 20 healthy controls were cultured with IL-18 in the presence of phytohemagglutinin (PHA) and IL-12 or IL-2. The levels of IFN-gamma, IL-13, and IL-4 in the culture supernatants were measured using enzymatic immunoassaying. IFN-gamma production was detected in all cultures from nonallergic controls stimulated with IL-18 in the presence of IL-12; however, the results for five BA patients and five AD patients were under the detection limit for IFN-gamma. In collaboration with IL-2, IL-18 was able to induce IFN-gamma production by PBMCs from all nonallergic controls and all allergic patients, with the exception of one AD patient. Synergistic induction of IL-13 production was found in cultures with IL-18 + IL-2, and the IL-13 induction was significantly increased in BA patients when compared with that in nonallergic controls (P = 0.006). The stimulation by IL-18, even in combination with IL-2, failed to induce IL-4 production by PBMC from both nonallergic controls and allergic patients. Although the induction of IFN-gamma by IL-18 + IL-12 was impaired in around a quarter of the allergic patients, the impairment of the IFN-gamma production was completely restored by IL-2 in the presence of IL-18. Thus, IL-18 enhances IFN-gamma production through an IL-12-dependent pathway and exhibits synergism when combined with IL-2 in terms of enhanced IL-13 and IFN-gamma production, suggesting the involvement of IL-18/IL-12/IL-2 pathway in modulating Th1/Th2 cytokine response.     

Prior elevation of IL-18 promotes rapid early IFN-gamma production during staphylococcal infection

Systemic Staphylococcus aureus infection is associated with significant morbidity and mortality arising from both bacterial and host immune factors. IL-18 is a pro-inflammatory cytokine of the IL-1 superfamily that exhibits broad functional effects in innate and acquired immune responses and which has been found in high levels in several chronic inflammatory and autoimmune diseases. Over-expression of IL-18 may promote early resolution of infection or could promote a detrimental exaggerated immune response. This was explored in a model of S. aureus infection. We report increased mortality in Swiss mice that were given recombinant IL-18 prior to inoculation with S. aureus LS-1. IL-18 administration prior to infection induced preferentially enhanced IFN-gamma mRNA expression in peripheral blood leukocytes and spleen, especially splenic NK cells. This correlated with increased IFN-gamma protein detection in serum, and leukocyte and spleen cultures at subsequent discrete time points. These data suggest that increased mortality following gram-positive infection in autoimmune diseases could in part reflect the impact of high levels of pleiotropic pro-inflammatory cytokines such as IL-18 present prior to the onset of infection.     

Pentoxifylline inhibits the synthesis and IFN-gamma-inducing activity of IL-18.

The effect of phosphodiesterase-inhibiting anti-inflammatory drug pentoxifylline (PTX) on LPS-induced IL-18 synthesis and IL-18-mediated IFN-gamma-induction were investigated. In a dose-dependent manner PTX inhibited production of IL-18 in LPS-treated cultures of murine spleen cells and bone marrow-derived macrophages. Similarly, PTX treatment significantly reduced blood IL-18 levels and expression of spleen IL-18 mRNA in LPS-challenged mice. The inhibitory effect of PTX was specific for IL-18, since LPS-induced IL-12 p40 release was not suppressed either in splenocyte cultures or blood of LPS-injected animals. Synergistic induction of IFN-gamma by combined IL-12/IL-18 treatment was also inhibited by PTX in vitro and in vivo. Experiments with IL-12 pretreatment of splenocytes, followed by IL-18 stimulation, revealed that PTX suppressed both IL-12 and IL-18 signals responsible for IFN-gamma induction. These results suggest that interference with IL-18 synthesis and IFN-gamma-inducing activity might contribute to anti-inflammatory actions of PTX.     

Up-regulation of IL-18 and predominance of a Th1 immune response is a hallmark of lupus nephritis

There is evidence that nephritis is dominated by a Th1 immune response in systemic lupus erythematosus. Since IL-18 promotes polarization of the immune response toward Th1, we investigated the role of this cytokine in lupus nephritis (LN). A total of 133 lupus patients and 44 healthy subjects were enrolled. Demographic and clinical characteristics with renal biopsy data were recorded. IL-18 along with IFN-gamma and IL-4, two prototypical of Th1 and Th2 cytokines, were measured in serum by ELISA. Peripheral blood lymphocytes were analysed by flow cytometry for IFN-gamma and IL-4. IL-18 expression was determined by immunohistochemistry in 13 renal biopsy specimens from patients with LN and 2 controls. Serum IL-18 was higher in lupus patients than in controls. Levels of IL-18 correlated with urinary microalbumin and were increased in patients with LN when compared to those without LN. IL-18 expression was also increased within the glomeruli of nephritic patients and was primarily detected within the mesangial matrix and in infiltrating mononuclear cells. Measurement of IFN-gamma and IL-4 in either sera or peripheral blood lymphocytes showed high IFN-gamma along with low IL-4 expression in LN patients compared to patients without nephritis. A positive correlation between serum IL-18 and IFN-gamma levels was found. IL-18 may play a prominent role in the pathogenesis of LN by promoting a cytokine imbalance towards a Th1 immune response. Measurement of IL-18 may be helpful for the early identification of lupus patients with LN and may help gauge the response to treatment in patients with active LN undergoing treatment.     

IFN-γ production in response to IL-18 or IL-12 stimulation by peripheral blood mononuclear cells of atopic patients

BACKGROUND: Several studies have shown that interleukin (IL)-4 and interferon-gamma (IFN-gamma) are important for the regulation of immunoglobulin E (IgE) production and that IL-18 and IL-12 induce IFN-gamma. OBJECTIVE: IFN-gamma production in response to IL-18 or IL-12 stimulation was investigated in peripheral blood mononuclear cells (PBMCs) of atopic patients with various levels of serum IgE. METHODS: Cytokine production from PBMCs was measured following stimulation with a non-specific stimulator (phytohemagglutinin: PHA), IL-18 or IL-12 in 12 healthy controls and 26 atopic patients with various serum IgE levels. RESULTS: IFN-gamma production by IL-18-stimulated PBMCs was positively correlated with IFN-gamma production by IL-12-stimulated PBMCs (P < 0.05). However some atopic patients showed discrepancy between the levels of IFN-gamma production stimulated by IL-12 and by IL-18. CONCLUSIONS: The results shown here suggest the presence of abnormalities in the IL-12 and/or IL-18 signalling pathways, such as genetic defects in the atopic patients.     

Increased plasma LIGHT levels in patients with atopic dermatitis

LIGHT [the name of which is derived from 'homologous to lymphotoxins, exhibits inducible expression, competes with herpes simplex virus glycoprotein D for herpes simplex virus entry mediator (HVEM), and expressed by T lymphocytes'], is a member of the tumour necrosis factor superfamily that is involved in various inflammatory diseases. We aimed to estimate the relevance of plasma LIGHT levels as a biomarker for atopic dermatitis (AD). In order to understand the putative role of LIGHT in AD pathogenesis, we also investigate the effects of LIGHT on a monocytic cell line, human acute monocytic leukaemia cell line (THP-1). We examined plasma LIGHT levels, total serum IgE, serum value of CCL17 and peripheral blood eosinophil counts in patients with AD and healthy subjects. The effects of LIGHT on activation and apoptosis in THP-1 cells were also investigated. The plasma concentrations of LIGHT in AD patients were significantly higher than those in healthy individuals and the concentrations decreased as the symptoms were improved by treatment. The LIGHT plasma concentrations correlated with IgE levels and the Severity Scoring of AD (SCORAD) index. In addition, LIGHT stimulation increased expression of CD86 and induced production of interleukin-1β in THP-1 cells. Apoptosis was inhibited, the Bcl-2 level increased and the caspase-3 level decreased in THP-1 cells stimulated with LIGHT, compared to unstimulated control cells. These results suggest that plasma LIGHT levels may be one of the promising biomarkers for AD.     

Gonadotropin treatment restores in vitro interleukin-1beta and tumour necrosis factor-alpha production by stimulated peripheral blood mononuclear cells from patients with idiopathic hypogonadotropic hypogonadism

In the present study, we aimed to investigate the effects of testosterone deficiency and gonadotropin therapy on the in vitro production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) by peripheral blood mononuclear cells (PBMCs) from patients with idiopathic hypogonadotropic hypogonadism (IHH) in order to elucidate the modulatory role of androgen in cytokine production. Fifteen male patients with untreated IHH and 15 age-matched healthy male subjects were enrolled in the study. Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), free testosterone (FT), sex hormone binding globulin (SHBG), prolactin, and IL-2 and IL-4 levels were also measured. In unstimulated cultures, IL-1beta and TNF-alpha secretion were not significantly different between patient and control groups. However, after stimulation with lipopolysaccharide (LPS), secretion of IL-1beta and TNF-alpha was significantly higher in cultures from untreated patients with IHH than in control subjects. Mean FSH, LH and FT levels were significantly lower, whereas SHBG, IL-2 and IL-4 levels were significantly higher in patients with IHH compared than in controls. In patients with IHH, FT negatively affected the serum levels of IL-4 and in vitro secretion of IL-1beta and TNF-alpha. In addition, IL-2 and IL-4 affected the in vitro secretion of IL-1beta in a positive manner. Gonadotropin therapy decreased both TNF-alpha and IL-1beta in PBMCs from patients with IHH. The levels of serum IL-2 and IL-4 were also decreased by therapy. In conclusion, in the present study, gonadotropin treatment restored the in vitro production of IL-1beta and TNF-alpha by PBMCs from patients with IHH, suggesting that androgen modulates proinflammatory cytokine production, at least directly through its effects on PBMCs. It seems probable that this effect plays an important role in the immunosuppressive action of androgens.     

Altered phenotype and function of blood dendritic cells in multiple sclerosis are modulated by IFN-beta and IL-10.

Multiple sclerosis (MS) is assumed to result from autoaggressive T cell-mediated immune responses, in which T helper type 1 (Th1) cells producing cytokines, e.g. IFN-gamma and lymphotoxin promote damage of oligodendrocyte-myelin units. Dendritic cells (DCs) as potent antigen presenting cells initiate and orchestrate immune responses. Whether phenotype and function of DCs with respect to Th1 cell promotion are altered in MS, are not known. This study revealed that blood-derived DCs from MS patients expressed low levels of the costimulatory molecule CD86. In addition, production of IFN-gamma by blood mononuclear cells (MNCs) was strongly enhanced by DCs derived from MS patients. IFN-beta and IL-10 inhibited the costimulatory capacity of DCs in mixed lymphocyte reaction (MLR) and showed additive effects on suppression of IL-12 production by DCs. Correspondingly, DCs pretreated with IFN-beta and IL-10 significantly suppressed IFN-gamma production by MNCs. IFN-beta in vitro also upregulated CD80 and, in particular, CD86 expression on DCs. In vitro, anti-CD80 antibody remarkably increased, while anti-CD86 antibody inhibited DC-induced IL-4 production in MLR. We conclude that DC phenotype and function are altered in MS, implying Th1-biased responses with enhanced capacity to induce Th1 cytokine production. In vitro modification of MS patients' DCs by IFN-beta and IL-10 could represent a novel way of immunomodulation and of possible usefulness for future immunotherapy of MS.     

Involvement of interleukin 18 in Crohn's disease: evidence from in vitro analysis of human gut inflammatory cells and from experimental colitis models

An imbalance of immunoregulatory factors and/or cells contributes to uncontrolled mucosal T cell activation and inflammation in Crohn's disease (CD). Bioactive interleukin (IL)-18 has been shown to be produced by macrophages in CD lesions. We report here that T cells freshly isolated from inflamed tissue of CD patients (and not T cells from control intestinal tissue) were responsive to IL-18. In the presence of IL-18, these T cells produced more interferon (IFN)-gamma and less IL-10. To analyse further the role of IL-18 in this disease, an acute and a chronic model of murine colitis were used. IL-18 mRNA was significantly enhanced in trinitrobenzene sulphonic acid (TNBS) induced colitis, and treatment with IL-18 binding protein (IL-18BPa), which neutralizes IL-18 bioactivity, significantly reduced the severity of colitis. However, IL-18BPa did not affect the course of chronic colitis in CD45RBhighCD4+ T cell reconstituted SCID mice. Production of IFN-gamma in lamina propria mononuclear cell cultures from IL-18BPa-treated SCID mice was decreased, but at the same time fewer lamina propria CD4+ T cells harvested from IL-18BPa-treated mice compared to non-treated mice were in apoptosis. We conclude that IL-18 clearly has a modulatory role in the inflammatory cascade of CD and experimental colitis by affecting IFN-gamma and IL-10 production, and apoptosis. In view of the divergent effects of IL-18 neutralization in the two different murine colitis models, it is unlikely that IL-18 is at the top of this cascade.