Regulatory T cells and inflammatory bowel disease

Changes in immune-related gene expression and intestinal lymphocyte subpopulations following Eimeria maxima infection of chickens

Coccidiosis, a major intestinal parasitic disease of poultry, induces a cell-mediated immune response against the etiologic agent of the disease, Eimeria. In the current study, the expression levels of gene transcripts encoding pro-inflammatory, Th1, and Th2 cytokines, as well as chemokines were measured in intestinal intraepithelial lymphocytes (IELs) after Eimeria maxima infection. In addition, changes in IEL numbers were quantified following E. maxima infection. Transcripts of the pro-inflammatory and Th1 cytokines IFN-gamma, IL-1beta, IL-6, IL-12, IL-15, IL-17, and IL-18 were increased 66- to 8 x 10(7)-fold following primary parasite infection. Similarly, mRNA levels of the Th2 cytokines IL-3, IL-10, IL-13, and GM-CSF were up-regulated 34- to 8800-fold, and the chemokines IL-8, lymphotactin, MIF, and K203 were increased 42- to 1756-fold. In contrast, IFN-alpha, TGF-beta4, and K60 transcripts showed no increased expression, and only the level of the Th2 cytokine IL-13 was increased following secondary E. maxima infection. Increases in intestinal T cell subpopulations following E. maxima infection also were detected. CD3(+), CD4(+), and CD8(+) cells were significantly increased at days 8, 6, and 7 post-primary infection, respectively, but only CD4(+) cells remained elevated following secondary infection. TCR1(+) cells exhibited a biphasic pattern following primary infection, whereas TCR2(+) cells displayed a single peak in levels. Taken together, these data indicate a global chicken intestinal immune response is produced following experimental Eimeria infection involving multiple cytokines, chemokines, and T cell subsets.

Analysis of chicken cytokine and chemokine gene expression following Eimeria acervulina and Eimeria tenella infections

The expression levels of mRNA encoding a panel of 28 chicken cytokines and chemokines were quantified in intestinal lymphocytes following Eimeria acervulina and Eimeria tenella primary and secondary infections. Compared with uninfected controls, transcripts of the pro-inflammatory cytokines IFN-alpha, IL-1beta, IL-6, and IL-17 were increased up to 2020-fold following primary infection. By contrast, following secondary infection by either microorganism, pro-inflammatory mRNAs levels were relatively unchanged (< or = 20-fold). Transcripts encoding the Th1 and Th1 regulatory cytokines IFN-gamma, IL-2, IL-10, IL-12, IL-15, IL-16, and IL-18 were uniformly increased 14-2471-fold after E. acervulina primary infection, but either unchanged (IL-15, IL-16, IL-18), increased (IFN-gamma, IL-10, IL-12), or decreased (IL-2) following E. tenella primary infection. Following secondary infections, Th1 cytokine mRNA levels were relatively unchanged, with the exception of IL-12 which was increased 1.5 x 10(5)-fold after E. acervulina and decreased 5.1 x 10(4)-fold after E. tenella infection. Transcripts for the Th2 or Th2 regulatory cytokines IL-3 and GM-CSF were increased up to 327-fold following primary or secondary infection with both parasites, while IL-4 and IL-13 mRNAs were decreased 25- to 2 x 10(5)-fold after primary or secondary infection. The dynamics of chicken chemokine expression revealed modest changes (<100-fold) following primary or secondary infection except for lymphotactin. When lymphocyte subpopulations were similarly analyzed, IFN-gamma, IL-2, IL-3, IL-15, and MIF were most highly increased in TCR2(+) cells following E. acervulina infection, while TCR1(+) cells only expressed high levels of IL-16 following E. tenella infection. In contrast, CD4(+) cells only expressed highest levels of IL-10 after E. acervulina infection, whereas these cells produced abundant transcripts for IFN-gamma, IL-3, IL-15, and MIF after E. tenella infection. We conclude that coccidiosis induces a diverse and robust primary cytokine/chemokine response, but a more subdued secondary response.

Dopamine D2 receptor polymorphisms in inflammatory bowel disease and the refractory response to treatment

Dopamine and its receptors may be involved in inflammatory reaction. The availability of this molecule depends on its receptors. The DRD2 gene, which codifies for the D2 dopamine receptor, has several polymorphisms. In this study, the DRD2 TaqIA polymorphism, which confers a decreased receptor density, was evaluated in 313 individuals including 220 inflammatory bowel disease patients (143 patients with Crohn's disease and 77 with ulcerative colitis) and in 93 healthy blood donors. The analysis was carried out by PCR-RFLP techniques. The frequencies of A (1) A (1) and A (2) A (2) genotypes were similar among Crohn's disease, ulcerative colitis patients, and health controls. Also, the genotype frequency was similar in different groups of disease localization, behavior, and age of disease onset. However, the Crohn's disease patients carriers of A (2) A (2) genotype showed a lower risk for development refractory Crohn's disease (37 out 65) than A (1) A (1) and A (1) A (2) carriers (28 out of 65) [(OR=0.4, 95% CI 0.21-0.87; p=0.02)]. Our results support an involvement of the dopamine receptor in inflammatory bowel disease and suggest a new potential target for therapy in refractory Crohn's disease patients.

Gliadin-specific type 1 regulatory T cells from the intestinal mucosa of treated celiac patients inhibit pathogenic T cells

Celiac disease (CD) results from a permanent intolerance to dietary gluten and is due to a massive T cell-mediated immune response to gliadin, the main component of gluten. In this disease, the regulation of immune responses to dietary gliadin is altered. Herein, we investigated whether IL-10 could modulate anti-gliadin immune responses and whether gliadin-specific type 1 regulatory T (Tr1) cells could be isolated from the intestinal mucosa of CD patients in remission. Short-term T cell lines were generated from jejunal biopsies, either freshly processed or cultured ex vivo with gliadin in the presence or absence of IL-10. Ex vivo stimulation of CD biopsies with gliadin in the presence of IL-10 resulted in suppression of Ag-specific proliferation and cytokine production, indicating that pathogenic T cells are susceptible to IL-10-mediated immune regulation. T cell clones generated from intestinal T cell lines were tested for gliadin specificity by cytokine production and proliferative responses. The majority of gliadin-specific T cell clones had a Th0 cytokine production profile with secretion of IL-2, IL-4, IFN-gamma, and IL-10 and proliferated in response to gliadin. Tr1 cell clones were also isolated. These Tr1 cells were anergic, restricted by DQ2 (a CD-associated HLA), and produced IL-10 and IFN-gamma, but little or no IL-2 or IL-4 upon activation with gliadin or polyclonal stimuli. Importantly, gliadin-specific Tr1 cell clones suppressed proliferation of pathogenic Th0 cells. In conclusion, dietary Ag-specific Tr1 cells are present in the human intestinal mucosa, and strategies to boost their numbers and/or function may offer new therapeutic opportunities to restore gut homeostasis.

PAS-1, a protein affinity purified from Ascaris suum worms, maintains the ability to modulate the immune response to a bystander antigen

Helminth infections and parasite components have potent immunomodulatory effects on a host's immune system. In the present study, we investigated the effect of PAS-1, a protein component of Ascaris suum adult worms recognized by a monoclonal antibody (MAIP-1), on humoral and cell-mediated responses to a bystander antigen (ovalbumin [OVA]). MAIP-1 recognized only one of the three polypeptide chains of PAS-1, but neutralized the suppressive effect of the whole worm extract on OVA-specific antibody production. PAS-1 inhibited antibody production against a T-cell-dependent, but not a T-cell-independent, antigen in a dose-dependent way. IgM, IgG1, IgG2b, and also IgE and anaphylactic IgG1 levels were downregulated. In addition, PAS-1 inhibited OVA-specific delayed type hypersensitivity reactions in the footpad of mice, showing a potent immunosuppressive activity on both Th1 and Th2 responses that seems to be mediated by the induction of large amounts of IL-10 and IL-4. Indeed, PAS-1-specific spleen cells secreted sevenfold more IL-10 and threefold more IL-4 than OVA-specific cells in response to in vitro restimulation with the respective antigens. In conclusion, we showed that PAS-1, a single protein component from A. suum, maintains all its immunosuppressive properties.

Stroke and T-cells

The microvasculature of the brain region affected by a stroke assumes an inflammatory phenotype that is characterized by endothelial cell activation and barrier dysfunction and the recruitment of adherent leukocytes. Although most attention has been devoted to the possible role of neutrophils in the tissue responses to ischemic stroke there is evidence that T-lymphocytes also accumulate in the postischemic brain. Although comparable detailed analyses of lymphocyte involvement in ischemic brain injury have not been performed, emerging findings suggest a role for T-cells in the pathogenesis of ischemic stroke. The recruitment of T-cells to the site of brain injury is critically dependent on the coordinated expression of adhesion molecules on the activated capillary endothelium. Whether the recruited lymphocytes are acting directly on brain tissue or indirectly through activation of other circulating blood cells and/or extravascular cells remain unclear. Cytotoxic CD8+ T-cells may induce brain injury through molecules released from their cytotoxic granules. CD4+ T-helper 1 (TH1) cells, which secrete proinflammatory cytokines, including interleukin-2 (IL-2), IL-12, interferon-gamma, and tumor necrosis factor-alpha, may play a key role in the pathogenesis of stroke, whereas CD4+TH2 cells may play a protective role through anti-inflammatory cytokines such as IL-4, IL-5, IL-10, and IL-13. T-cells should be considered as therapeutic targets for ischemic stroke. However, because infection is a leading cause of mortality in the postacute phase of ischemic stroke, and considering anti-inflammatory role of CD4+TH2, treatment targeting T-cells should be carefully designed to reduce deleterious and enhance protective actions of T-cells.

Evidence that scabies mites (Acari: Sarcoptidae) influence production of interleukin-10 and the function of T-regulatory cells (Tr1) in humans

We performed experiments to determine whether an extract of Sarcoptes scabiei (De Geer) influenced cytokine expression by human T-lymphocytes. Peripheral blood mononuclear cells from five sensitized donors and four donors without sensitization to scabies mites were challenged with a T-cell mitogen alone, with scabies extract (SS) alone, or with mitogen and SS together. Supernatants were analyzed for the cytokines interferon-gamma (IFNgamma), interleukin (IL)-2, IL-4, and IL-10. No IL-2 or IL-4 was produced in response to scabies extract. Cells from both naive and sensitized donors produced large amounts of IFNgamma and IL-10. The lack of IL-4 but high levels of IL-10 suggests that IL-10 was likely secreted by type 1 T-regulatory cells, which were activated by something in the scabies extract. IL-10 has anti-inflammatory and immune-suppressive effects. It may play a key role in depressing the inflammatory and immune responses in humans so that clinical symptoms are not seen until 4-6 wk after a person becomes infested with scabies mites.

Role of T-cell-associated lymphocyte function-associated antigen-1 in the pathogenesis of experimental colitis

The beta2 integrin lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18) is important for lymphocyte trafficking and activation as well as recruitment to sites of tissue inflammation. The objective of this study was to assess the role of 'T-cell-associated' LFA-1 in the pathogenesis of chronic colitis in vivo. Transfer of CD4+CD25- T cells isolated from wild-type (wt) mice into immunodeficient recipients [recombinase-activating gene-1-deficient (RAG-1-/-] produced moderate to severe colitis, whereas RAG-1-/- mice injected with CD11a-deficient (CD11a-/-; LFA-1-/-) donor T cells displayed minimal macroscopic and histological evidence of colitis. Surface expression of L-selectin, alpha4, alpha4beta7 and chemokine receptor-7 were similar for wt and CD11a-/- donor T cells. Attenuated disease in the CD11a-/- --> RAG-1-/- animals was associated with decreased numbers of CD4+ T cells in the mesenteric lymph nodes (MLNs), spleen and intestinal lamina propria (LP). In addition, significant reductions in Th1 cytokines were observed following ex vivo stimulation of mononuclear cells obtained from the MLNs and colonic LP. Interestingly, mononuclear cells obtained from the spleens of CD11a-/- --> RAG-1-/- exhibited enhanced pro-inflammatory cytokine production compared with splenocytes obtained from wt --> RAG-1-/- colitic mice. Taken together, our data suggest that T-cell-associated CD11a (LFA-1) expression plays a dual role in the initiation of chronic gut inflammation by facilitating naive T-cell priming/activation and expansion within MLNs and by augmenting pro-inflammatory cytokine production following secondary stimulation by antigen-presenting cells in the colonic interstitium.

Natural killer cells in Bal and peripheral blood of patients with idiopathic pulmonary fibrosis (IPF)

Idiopathic Pulmonary Fibrosis/ Usual Interstitial Pneumonia (IPF/UIP) represents the most important interstitial pneumonia. ATh2 cytokine pathway predominance, favoring collagen deposition, associated to a deficit in (IFN- gamma) network, seems to be involved in the pathogenesis of this disease. Nonetheless, few data are available about the potentially involved cells. Natural killer cells (NK), are one of the most important subsets implicated in the IFN-gamma network. The aim of this study was to assess NK cells, both in BAL and peripheral blood of 11 patients suffering from IPF (group A) with respect to 11 patients with other interstitial pneumonia (Group B). Our results did not show any statistically significant difference in NK percentage in BAL between group A and B. On the contrary, patients with IPF showed a higher percentage of NK cells (t = 2.41; p < 0.05) and absolute number of cells (t = 2.32; p < 0.05) in peripheral blood, as well as a strong positive correlation between circulating and BAL NK cells (r = 0.69; p < 0.05). This finding shows, for the first time, a relationship between peripheral and lung resident cell environments in humans suggesting a possible systemic involvement in the natural history of IPF.

Enhanced oral tolerance in transgenic mice with hepatocyte secretion of IL-10

Several cytokines derived from Th3 and Tr1 cells, including IL-10, are believed to regulate oral tolerance, but direct evidence is lacking. We have explored the potential role of IL-10 by generating transgenic (TG) mice with sustained hepatocyte-specific expression of rat IL-10. TG mice expressed rat IL-10 downstream of a transthyretin promoter, which led to serum levels that were increased 10- to 100-fold compared with normal animals. Animals were orally administered 1 mg of whole OVA for 5 consecutive days, with control animals receiving PBS. There were six animal groups: Either OVA or PBS were fed orally to rat IL-10 TG mice, non-TG wild-type mice without IL-10 administration, and non-TG wild-type mice administered rat IL-10 systemically. On day 8, all mice were immunized with two injections of OVA, and then analyzed on day 18. T cell proliferation responses were reduced by 65.8 +/- 14.3% after feeding of OVA in rIL-10 TG animals, compared with 39.4 +/- 15.6% in the non-TG mice (p = 0.02). Anti-OVA titers were expressed as fold increase over naive non-TG mice. After feeding, titers decreased by approximately 33% (from 3- to 2-fold) in TG animals and, to a lesser extent, in non-TG animals. IFN-gamma secretion by cultured popliteal lymphocytes decreased in TG animals by 83% after feeding and by 69% in non-TG animals. IL-4 secretion increased 4-fold in TG-fed mice, but did not significantly change in non-TG OVA-fed animals. In contrast to hepatic TG expression of rIL-10, systemic administration of rIL-10 had only a modest effect on tolerance. IL-10, when transgenically expressed in the liver enhances mucosal tolerance to an oral Ag.

Modulation of surgical fibrosis by microbial zwitterionic polysaccharides

Bacterial carbohydrates have long been considered T cell-independent antigens that primarily induce humoral immune responses. Recently, it has been demonstrated that bacterial capsules that possess a zwitterionic charge motif can activate CD4(+) T cells after processing and presentation by antigen-presenting cells. Here we show that these zwitterionic polysaccharides can prevent T helper 1-mediated fibrosis by signaling for the release of IL-10 from CD4(+) T cells in vivo. IL-10 production by these T cells and their ability to prevent fibrosis is controlled by the inducible costimulator (ICOS)-ICOS ligand pathway. These data demonstrate that the interaction of the zwitterionic polysaccharides with T cells results in modulation of surgical fibrosis in vivo and suggest a previously undescribed approach to "harnessing" T cell function to prevent inflammatory tissue disorders in humans.

Thymic regulatory T cells

Several types of T regulatory (Treg) cells have been described in both mice and humans, including natural or professional (CD4+CD25+ T cells) and adaptive (Th3 and Tr1 cells) Treg cells. The former develops in the thymus and results in an endogeneous long-lived population of self-antigen-specific T cells in the periphery poised to prevent potentially autoimmune reactions. The second subset develops as a consequence of activation of mature T cells under particular conditions of sub-optimal antigen exposure and/or costimulation. Natural Treg cells are positively selected in the cortex through their TCR interactions with self-peptides presented by thymic stromal cells. It is likely that this high-affinity recognition results in signals rendering them anergic and able to produce anti-apoptoptic molecules which protect them from negative selection. Recently, small subsets of CD4+CD25+ and of CD8+CD25+ cells sharing similar characteristics have been detected in human fetal and post-natal thymuses. Both CD4+CD25+ and CD8+CD25+ human thymocytes express Foxp3 and GITR mRNA, as well as surface CCR8 and TNFR2 and cytoplasmic CTLA-4 proteins, which are common features of mature Treg cells. Following activation they do not proliferate or produce cytokines, but express surface CTLA-4 and TGF-beta1. They suppress the proliferation of autologous CD4+CD25- thymocytes to allogeneic stimulation by a contact-dependent mechanism related to the combined action of surface CTLA-4 and TGF-beta leading to the inhibition of the IL-2R alpha chain on target T cells. Lastly, both CD4+CD25+ and CD8+CD25+ Treg thymocytes exert strong suppressive activity on Th1, but much lower on Th2 cells, since these latter may escape from suppression via their ability to respond to growth factors other than IL-2. Treg cells that develop in, and emerge from, the thymus are certainly responsible for the maintenance of self-tolerance and prevention of autoimmune disorders. The result that Th1 cells are highly susceptible to the suppressive activity of Treg thymocytes is consistent with the important role of these cells in protecting against the Th1-mediated immune response to autoantigens.

IL-4 and IL-10 are essential for immunosuppression induced by high molecular weight proteins from Ascaris suum

The extract from Ascaris suum worms (Asc) impairs Th1 and Th2 responses to a non-related antigen, i.e. ovalbumin (OVA). Its suppressive capacity is due to high molecular weight components present in a gel filtration fraction (PI). This fraction is able to elicit IL-4 and IL-10 secretion. Interestingly enough, it induces anti-PI non-anaphylactic IgG1 synthesis through the action of IL-12/IFN-gamma. Here, we investigated the down-regulation of the immune response to OVA by PI in IL-12, IFN-gamma, IL-4 or IL-10 C57BL/6 knockout mice immunized with OVA+PI in adjuvant. OVA-induced delayed-type hypersensitivity (DTH) reactions, secretion of IL-2 and IFN-gamma, and IgG1, IgG2c and IgE antibody production were suppressed by PI in wild-type mice, as well as in IL-12- or IFN-gamma-deficient mice. In contrast, PI had no effect on anti-OVA IgE production and DTH, and induced only a partial suppression of IgG1 and IFN-gamma in IL-10(-/-) mice. The experiments also showed that IL-4 was involved in the PI-induced suppression of IgG2c antibodies and IL-2 secretion. Finally, down-regulation of IFN-gamma was not seen in mice lacking both IL-4 and IL-10, i.e. IL-4(-/-) mice treated with anti-IL-10 antibodies before immunization. These results exclude the participation of IL-12 and IFN-gamma in PI-induced immunosuppression, and highlight the essential role of IL-10 in the suppression of OVA-specific Th2-related parameters, as well as the cooperation between IL-10 and IL-4 in the suppression of Th1-related parameters.

Intestinal Fibroblast-Derived IL-10 Increases Survival of Mucosal T Cells by Inhibiting Growth Factor Deprivation- and Fas-Mediated Apoptosis

Mucosal T cells are essential to immune tolerance in the intestine, an organ constantly exposed to large amounts of dietary and bacterial Ags. We investigated whether local fibroblasts affect mucosal T cell survival, which is critical for maintenance of immune tolerance. Coculture with autologous fibroblasts significantly increased viability of mucosal T cells by inhibiting IL-2 deprivation- and Fas-mediated apoptosis, an effect that was both contact- and secreted product-dependent. Investigation of anti-apoptotic factors in the fibroblast-conditioned medium (FCM) revealed the presence of IL-10 and PGE2, but not IFN-beta, IL-2, or IL-15. Although recombinant IFN-beta, but not PGE2, effectively prevented T cell apoptosis, neutralizing Ab studies showed that only IL-10 blockade significantly increased T cells apoptosis, whereas neutralizing IFN-beta or IFN-alpha failed to inhibit the anti-apoptotic effect of FCM. To confirm that fibroblast-derived IL-10 was responsible for preserving mucosal T cell viability, IL-10 mRNA was demonstrated in fibroblasts by Southern blotting and RT-PCR. When FCM was submitted to HPLC fractionation, only the peak matching rIL-10 contained the anti-apoptotic activity, and this was eliminated by treatment with an IL-10-neutralizing Ab. Finally, when fibroblasts were transiently transfected with IL-10 antisense oligonucleotides, the conditioned medium lost its T cell anti-apoptotic effect, whereas medium from fibroblasts transfected with IFN-beta antisense oligonucleotides displayed the same anti-apoptotic activity of medium from untransfected fibroblasts. These results indicate that local fibroblast-derived IL-10 is critically involved in the survival of mucosal T cells, underscoring the crucial importance of studying organ-specific cells and products to define the mechanisms of immune homeostasis in specialized tissue microenvironments like the intestinal mucosa.

Functional features of human CD25+ regulatory thymocytes

Two families of Treg cells have been described and named "naturally occurring" and "adaptive" regulatory T cells. The naturally occurring Treg cells arise in the thymus, where they achieve their complete functional maturation, whereas the adaptive Treg cells derive from the thymus too, but achieve their functional maturation in the periphery. This review discusses the phenotype and the functional features of the human naturally occurring CD25+ regulatory thymocytes.

Platelet factor 4 differentially modulates CD4+CD25+ (regulatory) versus CD4+CD25- (nonregulatory) T cells

Active suppression mediated by CD4(+)CD25(+) T regulatory (Tr) cells plays an important role in the down-regulation of T cell responses to both foreign and self-Ags. Platelet factor 4 (PF4), a platelet-derived CXC chemokine, has been shown to strongly inhibit T cell proliferation as well as IFN-gamma and IL-2 release by isolated T cells. In this report we show that human PF4 stimulates proliferation of the naturally anergic human CD4(+)CD25(+) Tr cells while inhibiting proliferation of CD4(+)CD25(-) T cells. In coculture experiments we found that CD4(+)CD25(+) Tr cells exposed to PF4 lose the ability to inhibit the proliferative response of CD4(+)CD25(-) T cells. Our findings suggest that human PF4, by inducing Tr cell proliferation while impairing Tr cell function, may play a previously unrecognized role in the regulation of human immune responses. Because platelets are the sole source of PF4 in the circulation, these findings may be relevant to the pathogenesis of certain immune-mediated disorders associated with platelet activation, such as heparin-induced thrombocytopenia and autoimmune thrombocytopenic purpura.

Regional intestinal adaptations in Na+,K+-ATPase in experimental colitis and the contrasting effects of interferon-gamma

AIMS

This study evaluated Na+,K+-ATPase activity and the abundance of alpha1 subunit Na+,K+-ATPase in experimental colitis and gathered evidence on the effects of interferon-gamma (IFN-gamma) on intestinal Na+,K+-ATPase.

METHODS

Colitis was induced by the intrarectal administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS, 30 mg/250 microL). Na+,K+-ATPase activity was determined as the difference between total and ouabain-insensitive ATPase. The abundance of Na+,K+-ATPase was analysed by immunoblotting.

RESULTS

Na+,K+-ATPase activity was markedly reduced in the proximal colonic mucosa of TNBS-treated rats, whereas upstream in the terminal ileal mucosa a marked increase in sodium pump activity was observed. At the jejunal level no significant changes in Na+,K+-ATPase activity were observed between TNBS-treated rats and corresponding controls (ethanol-treated rats). No changes were observed in the abundance of alpha1 subunit Na+,K+-ATPase in the proximal colon, terminal ileum and jejunum. The administration of IFN-gamma (50,000 U) 48 h before sacrifice reduced both Na+,K+-ATPase activity and the abundance of alpha1 subunit Na+,K+-ATPase in the proximal colon. Dexamethasone prevented colonic inflammation and decreases in proximal colonic Na+,K+-ATPase activity in TNBS-treated rats, but did not affect the INF-gamma-induced decrease in colonic Na+,K+-ATPase activity.

CONCLUSIONS

The increase in ileal Na+,K+-ATPase activity upstream to the lesioned colonic mucosa, where Na+,K+-ATPase activity was markedly reduced, might indicate a compensatory process to counteract the decrease in water and electrolyte absorption at the colonic level. This decrease in colonic Na+,K+-ATPase activity is likely not related to INF-gamma-induced downregulation of Na+,K+-ATPase.

New lessons from old pathogens: what parasitic infections have taught us about the role of nuclear factor-kappaB in the regulation of immunity

The nuclear factor-kappaB (NF-kappaB) family of transcription factors is activated by many infectious and inflammatory stimuli. This family regulates the expression of multiple genes, whose products include cytokines, chemokines, adhesion molecules, and antiapoptotic factors that are important components of the innate and adaptive immune response. A prominent role of NF-kappaB transcription factors in resistance to a variety of infectious diseases was revealed by studies with mice that lack individual family members. However, little is known about the basis for these effects or about the role of individual family members during a coordinated immune response to infection. Diverse parasites such as Toxoplasma gondii, Leishmania major, and Trichuris muris provide a unique opportunity to understand the role of the NF-kappaB system in the development of innate and adaptive immunity to these infections. The basis for resistance and susceptibility to these parasites is well understood, and studies using these experimental systems have provided unique insights into the role of NF-kappaB in the regulation of T-helper 1 cell (Th1) and Th2 type responses. It has become clear that NF-kappaB family members have cell lineage-specific functions and that their relative importance varies with type of infection as well as route of pathogen entry. Thus, studies with models of parasitic infection have revealed that individual NF-kappaB family members perform distinct, nonoverlapping, and biologically significant functions in the regulation of immunity and inflammation.

Intestinal epithelial cells synthesize glucocorticoids and regulate T cell activation

Glucocorticoids (GCs) are important steroid hormones with widespread activities in metabolism, development, and immune regulation. The adrenal glands are the major source of GCs and release these hormones in response to psychological and immunological stress. However, there is increasing evidence that GCs may also be synthesized by nonadrenal tissues. Here, we report that the intestinal mucosa expresses steroidogenic enzymes and releases the GC corticosterone in response to T cell activation. T cell activation causes an increase in the intestinal expression of the steroidogenic enzymes required for GC synthesis. In situ hybridization analysis revealed that these enzymes are confined to the crypt region of the intestinal epithelial layer. Surprisingly, in situ-produced GCs exhibit both an inhibitory and a costimulatory role on intestinal T cell activation. In the absence of intestinal GCs in vivo, activation by anti-CD3 injection resulted in reduced CD69 expression and interferon-gamma production by intestinal T cells, whereas activation by viral infection led to increased T cell activation. We conclude that the intestinal mucosa is a potent source of immunoregulatory GCs.

Depletion of CD25+ cells from human T-cell enriched fraction eliminates immunodominance during priming with dendritic cells genetically modified to express a secreted protein

The ability of dendritic cells (DCs), genetically modified with one of two types of plasmid DNA vaccines to stimulate lymphocytes from normal human donors and to generate antigen-specific responses, is compared. The first type, also called "secreted" vaccine (sVac), encodes for the full length of the human prostate-specific antigen (PSA) with a signal peptide sequence so that the expressed product is glycosylated and directed to the secretory pathway. The second type, truncated vaccines (tVacs), encodes for either hPSA or human prostate acidic phosphatase (hPAP), both of which lack signal peptide sequences and are retained in the cytosol and degraded by the proteasomes following expression. Monocyte-derived dendritic cells are transiently transfected with either sVac or one of two tVacs. The DCs are then used to activate CD25+-depleted or nondepleted autologous lymphocytes in an in vitro model of DNA vaccination. Lymphocytes are boosted following priming with transfected DCs, peptide-pulsed DCs or monocytes. Their reactivity is tested against tumor cells or peptide-pulsed T2 target cells. Both tVacDCs and sVacDCs generate antigen-specific cytotoxic T-cell responses. The immune response is restricted towards one of the three antigen-derived epitopes when priming and boosting is performed with sVacDCs. In contrast, tVac-transfected DCs prime T cells towards all antigen-derived epitopes. Subsequent repeated boosting with transfected DCs, however, restricts the immune response to a single epitope due to immunodominance. While CD25+ cell depletion prior to priming with sVacDCs alleviates immunodominance, cotransfection of dendritic cells with GITR-L does so in some but not all cases.

Deficiencies in gut NK cell number and function precede diabetes onset in BB rats

Defects in the intestinal immune system may contribute to the pathogenesis of autoimmune diseases. Intraepithelial lymphocytes represent a substantial fraction of gut-associated lymphocytes, but their function in mucosal immunity is unclear. A newly described population of NK cells that spontaneously secrete IL-4 and IFN-gamma is present in the intraepithelial lymphocyte compartment of the rat. We hypothesized that defects in the number or function of these cells would be present in rats susceptible to autoimmunity. We report that the number of NKR-P1A(+)CD3(-) intraepithelial NK (IENK) cells is deficient before onset of spontaneous autoimmune diabetes in diabetes-prone BB (BBDP) rats. The absolute number of recoverable IENK cells was only approximately 8% of that observed in WF rats. Bone marrow transplantation from histocompatible WF donors reversed the IENK cell deficiency (and prevented diabetes) in these animals, suggesting a hemopoietic origin for their IENK cell defect. Analysis of diabetes-resistant BB rats, which develop autoimmune diabetes only after perturbation of the immune system, revealed IENK cell numbers intermediate between that of BBDP and WF rats. IENK cells were selectively depleted during treatment to induce diabetes. Prediabetic BBDP and diabetes-resistant BB animals also exhibited defective IENK cell function, including decreased NK cell cytotoxicity and reduced secretion of IL-4 and IFN-gamma. IENK functional defects were also observed in LEW and BN rats, which are susceptible to induced autoimmunity, but not in WF, DA, or F344 rats, which are resistant. Defects in IENK cell number and function may contribute to the pathogenesis of autoimmune diseases including type 1 diabetes.

Intestinal Na+-K+-ATPase activity and molecular events downstream of interferon-gamma receptor stimulation

This study evaluated the effects of human interferon-gamma (IFN-gamma) on Na(+)-K(+)-ATPase activity and the intracellular signaling pathways involved in human intestinal epithelial Caco-2 cells. Na(+)-K(+)-ATPase activity was determined as the difference between total and ouabain-sensitive ATPase. p38 MAP kinase activity was analyzed by Western blotting using the p38 MAP kinase assay kit. Total and phosphorylated STAT1 protein levels were detected using the PhosphoPlus Stat1. IFN-gamma decreased Na(+)-K(+)-ATPase activity in a time- and concentration-dependent manner. The IFN-gamma-induced decrease in Na(+)-K(+)-ATPase activity was accompanied by no changes in the abundance of alpha(1) subunit Na(+)-K(+)-ATPase. Downregulation of protein kinase C (PKC) with phorbol-12,13-dibutyrate (PDBu) prevented the inhibitory effect of IFN-gamma on Na(+)-K(+)-ATPase activity. Inhibition of Raf-1, mitogen-activated protein kinase kinase (MAPKK/MEK), p38 MAPK and STAT1 with, respectively, GW 5074, PD 98059, SB 203580 and epigallocatechin gallate prevented inhibition of Na(+)-K(+)-ATPase activity by IFN-gamma. Treatment with IFN-gamma markedly increased the expression of total and phospho-STAT1, this being accompanied by activation of p38 MAPK. Activation of phospho-STAT1 by IFN-gamma was almost abolished by epigallocatechin gallate and markedly reduced by SB 203580, but insensitive to downregulation of PKC. The increase in short circuit current (I(sc)) by 1.0 and 2.5 micrograms ml(-1) amphotericin B was markedly attenuated in IFN-gamma-treated cells. However, the inhibitory effect of PDBu on the amphotericin B-induced increase in I(sc) was of similar magnitude in vehicle- and IFN-gamma-treated cells. It is concluded that IFN-gamma markedly attenuates Na(+)-K(+)-ATPase activity. The transduction mechanisms set into motion by IFN-gamma involve the activation of PKC downstream STAT1 phosphorylation and Raf-1, MEK, ERK2 and p38 MAPK pathways, in a complex sequence of events.

Human dendritic cells genetically engineered to express cytosolically retained fragment of prostate-specific membrane antigen prime cytotoxic T-cell responses to multiple epitopes

The ability of two plasmid DNA vaccines to stimulate lymphocytes from normal human donors and to generate antigen-specific responses is demonstrated. The first vaccine (truncated; tPSMA) encodes for only the extracellular domain of prostate-specific membrane antigen (PSMA). The product, expressed following transfection with this vector, is retained in the cytosol and degraded by the proteasomes. For the "secreted" (sPMSA) vaccine, a signal peptide sequence is added to the expression cassette and the expressed protein is glycosylated and directed to the secretory pathway. Monocyte-derived dendritic cells (DCs) are transiently transfected with either sPSMA or tPSMA plasmids. The DCs are then used to activate autologous lymphocytes in an in vitro model of DNA vaccination. Lymphocytes are boosted following priming with transfected DCs or with peptide-pulsed monocytes. Their reactivity is tested against tumor cells or peptide-pulsed T2 target cells. Both tPSMA DCs and sPSMA DCs generate antigen-specific cytotoxic T-cell responses. The immune response is restricted toward one of the four PSMA-derived epitopes when priming and boosting is performed with sPSMA. In contrast, tPSMA-transfected DCs prime T cells toward several PSMA-derived epitopes. Subsequent repeated boosting with transfected DCs, however, restricts the immune response to a single epitope due to immunodominance.

Aging, autoimmunity and arthritis: T-cell senescence and contraction of T-cell repertoire diversity - catalysts of autoimmunity and chronic inflammation

Rheumatoid arthritis (RA), like many other autoimmune syndromes, is a disease of adults, with the highest incidence rates reported in the elderly. The immune system undergoes profound changes with advancing age that are beginning to be understood and that need to be incorporated into the pathogenetic models of RA. The age-related decline in thymic function causes extensive remodeling of the T-cell system. Age-dependent changes in T-cell homeostasis are accelerated in patients with RA. The repertoire of naive and memory T cells is less diverse, possibly as a result of thymic insufficiency, and it is biased towards autoreactive cells. Presenescent T cells emerge that are resistant to apoptosis and that often expand to large clonal populations. These cells are under the regulatory control of nonconventional costimulatory molecules, display potent effector functions, and appear to be critical in the synovial and extra-articular manifestations of RA.

Expression of dual TCR on DO11.10 T cells allows for ovalbumin-induced oral tolerance to prevent T cell-mediated colitis directed against unrelated enteric bacterial antigens

The triggering Ag for inflammatory bowel disease and animal models of colitis is not known, but may include gut flora. Feeding OVA to DO11.10 mice with OVA-specific transgenic (Tg) TCR generates Ag-specific immunoregulatory CD4(+) T cells (Treg) cells. We examined the ability of oral Ag-induced Treg cells to suppress T cell-mediated colitis in mice. SCID-bg mice given DO11.10 CD4(+)CD45RB(high) T cells developed colitis, and cotransferring DO11.10 CD45RB(low)CD4(+) T cells prevented CD4(+)CD45RB(high) T cell-induced colitis in the absence of OVA. The induction and prevention of disease by DO11.10 CD4(+) T cell subsets were associated with an increase in endogenous TCRalpha chain expression on Tg T cells. Feeding OVA to SCID-bg mice reconstituted with DO11.10 CD4(+)CD45RB(high) attenuated the colitis in association with increased TGF-beta and IL-10 secretion, and decreased proliferative responses to both OVA and cecal bacteria Ag. OVA feeding also attenuated colitis in SCID-bg mice reconstituted with a mix of BALB/c and DO11.10 CD45RB(high) T cells, suggesting that OVA-induced Treg cells suppressed BALB/c effector cells. The expression of endogenous non-Tg TCR allowed for DO11.10-derived T cells to respond to enteric flora Ag. Furthermore, feeding OVA-induced Treg cells prevented colitis by inducing tolerance in both OVA-reactive and non-OVA-reactive T cells and by inducing Ag-nonspecific Treg cells. Such a mechanism might allow for Ag-nonspecific modulation of intestinal inflammation in inflammatory bowel disease.

Autoreactive T Cells in Healthy Individuals

The presence of autoreactive CD4(+) T cells in the peripheral blood of healthy human subjects was investigated after removal of CD4(+)CD25(+) regulatory T cells (Treg). CD4(+) T cells that were directed against the type 1 diabetes-associated autoantigen glutamic acid decarboxylase 65, the melanocyte differentiation Ag tyrosinase, and the cancer/testis tumor Ag NY-ESO-1 were readily derived from PBMC of healthy individuals. These autoreactive T cells could be visualized, using Ag-specific class II tetramer reagents, in the peripheral blood of most individuals examined. Addition of CD4(+)CD25(+) Treg back to the CD4(+)CD25(-) population suppressed the expansion of the autoreactive T cells. Autoreactive T cells were cloned based on tetramer binding, and expressed characteristic activation markers upon self-Ag stimulation. These results show that autoreactive T cells are present in most healthy individuals and that Treg likely play an important role of keeping these autoreactive T cells in check.

Ultraviolet radiation-induced regulatory T cells not only inhibit the induction but can suppress the effector phase of contact hypersensitivity

Epicutaneous application of haptens to UV-exposed skin induces hapten-specific tolerance. This is mediated via regulatory T cells (Tr), as i.v. injection of T cells from UV-tolerized mice into naive animals renders the recipients unresponsive to the respective hapten. However, when UV-induced Tr are injected i.v. into sensitized mice, contact hypersensitivity (CHS) is not suppressed, suggesting that Tr inhibit the induction, but not the elicitation, of CHS and are inferior to T effector cells. As sensitization takes place in the lymph nodes, but elicitation occurs in the area of challenge, we postulated that Tr injected i.v. locate to the lymph nodes and not to the periphery and therefore only suppress the induction, not the elicitation, of CHS. Indeed, i.v. injection of Tr into sensitized mice did not inhibit CHS, although injection of Tr into the ears of sensitized mice suppressed the challenge. Inhibition was hapten specific, as injection of dinitrofluorobenzene (DNFB)-specific Tr into the ears of oxazolone (OXA)-sensitized mice did not affect challenge with OXA. However, when ears of OXA-sensitized mice were injected with DNFB-specific Tr and painted with DNFB before OXA challenge, CHS was suppressed. Inhibition correlated with the local expression of IL-10. Depletion studies and FACS analysis revealed that Tr express the lymph node-homing receptor L-selectin, but not the ligands for the skin-homing receptors E- and P-selectin, suggesting that UV-induced Tr, although able to inhibit T effector cells, do not suppress the elicitation of CHS upon i.v. injection, because they obviously do not migrate into the skin.

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IL-10 and its related cytokines for treatment of inflammatory bowel disease

Inflammatory bowel diseases (IBDs), including Crohn’s disease and ulcerative colitis are chronic inflammatory disorders of gastrointestinal tract. Although the etiology is incompletely understood, initiation and aggravation of the inflammatory process seem to be due to a massive local mucosal immune response. Interleukin-10 (IL-10) is a regulatory cytokine which inhibits both antigen presentation and subsequent pro-inflammatory cytokine release, and it is proposed as a potent anti-inflammatory biological therapy in chronic IBD. Many methods of IL-10 as a treatment for IBD have been published. The new strategies of IL-10 treatment, including recombinant IL-10, the use of genetically modified bacteria, gelatine microsphere containing IL-10, adenoviral vectors encoding IL-10 and combining regulatory T cells are discussed in this review. The advantages and disadvantages of these IL-10 therapies are summarized. Although most results of recombinant IL-10 therapies are disappointing in clinical testing because of lacking efficacy or side effects, therapeutic strategies utilizing gene therapy may enhance mucosal delivery and increase therapeutic response. Novel IL-10-related cytokines, including IL-19, IL-20, IL-22, IL-24, IL-26, IL-28 and IL-29, are involved in regulation of inflammatory and immune responses. The use of IL-10 and IL-10-related cytokines will provide new insights into cell-based and gene-based treatment against IBD in near future.

Spontaneous T(H)1 cytokine production by intraepithelial but not circulating T cells in infants with or without food allergies

BACKGROUND

It has been established that the maintenance of immunological tolerance to dietary antigen and the intestinal flora (oral tolerance) is an actively-maintained process dependent upon mucosal lymphocyte populations. Early life exposures appear critical in the development of such tolerance. However little is known about the activation status of mucosal lymphocytes in human infancy and childhood.

PATIENTS AND METHODS

We have performed flow cytometric analysis for cell lineage and cytokine-production status in peripheral blood and duodenal intraepithelial lymphocytes taken during endoscopy from 20 children [median age 2.9 +/- 0.6 years (median +/- SE)] in whom investigation found no intestinal abnormalities (histologically normal controls) and 30 children (median age 1.6 +/- 0.4 years) with confirmed allergy to cow's milk and other dietary antigens.

RESULTS

Regardless of clinical status, spontaneous production of cytokines was low or undetectable in peripheral blood cells. By contrast, intraepithelial CD4 and CD8 cells isolated from the small intestine were often activated, with 5% or more showing spontaneous production of T(H)1 type [interleukin-2, interferon (IFN)-gamma] cytokines in both normal controls and food-allergic children. Stimulation in vitro strongly induced cytokine production in peripheral blood but not intraepithelial lymphocytes. Immunohistochemistry showed similar density of IFN-gamma(+) intraepithelial lymphocytes in controls and allergic children.

CONCLUSIONS

Duodenal intraepithelial lymphocytes in human infants show a state of increased spontaneous activation compared with peripheral blood lymphocytes, and show no significant impairment of T(H)1 responses in food allergic children.

A comparative study between T regulatory type 1 and CD4+CD25+ T cells in the control of inflammation

There is now compelling evidence that CD4(+)CD25(+) T cells play a major role in the maintenance of tolerance. Besides CD4(+)CD25(+) T cells, different populations of regulatory CD4(+) T cells secreting high amounts of IL-10 (T regulatory type 1 (Tr1)) or TGF-beta (Th3) have also been described in in vivo models. In the lymphocyte transfer model of inflammatory bowel disease, we show here that the control of inflammation during the first weeks is not due to a complete inhibition of differentiation of aggressive proinflammatory T cells, but is the result of a balance between proinflammatory and Tr cells. We also show that in the first weeks continuous IL-10 secretion was required to actively control inflammation. Indeed, treatment with anti-IL-10R Abs 3 wk after the start of the experiment completely reversed the protective effect of Tr cells. IL-10 secretion and control of inflammation could be provided by late injection of Tr1 cells that efficiently cure ongoing inflammatory responses in two different models of inflammation. In contrast, inflammation was not controlled when high numbers of CD4(+)CD45RB(low) or CD4(+)CD25(+) T cells were injected as early as 1 wk after the start of the experiment. These results confirm in vitro studies showing that CD4(+)CD45RB(low) do not contain high IL-10-producing cells and suggest that CD4(+)CD45RB(low) Tr cells maintain tolerance in vivo, in part indirectly, through the differentiation of IL-10-secreting Tr1 cells.

Demonstration of strong enterobacterial reactivity of CD4+CD25-T cells from conventional and germ-free mice which is counter-regulated by CD4+CD25+T cells

Unfractionated CD4+ T cells from the gut-associated lymphoid tissue (GALT) and peripheral lymph nodes are unresponsive when exposed to enterobacterial antigens in vitro. Under similar conditions, CD4+ T cells depleted in vivo or in vitro of CD4+CD25+ T cells proliferate extensively. The CD4+CD25- T cell reactivity depends on MHC class II presentation, specific TCR stimulation, CD4 ligation, and antigen processing by antigen-presenting cells. The CD4+CD25- T cells respond to autologous and heterologous enterobacterial antigens, but not to antigens from the feces of germ-free mice. Surprisingly, CD4+CD25- T cells obtained from the GALT of germ-free mice also proliferate when exposed to enterobacterial antigens, and adding back the conventional or germ-free CD4+CD25+ T cells to the enteroantigen-stimulated CD4+CD25- T cells abolishes proliferation. As judged from carboxyfluorescein diacetate succinimidyl ester-labeling experiments, 4-5% of the CD4+CD25- T cells respond to enteroantigen. The data show for the first time that CD4+CD25- T cells with reactivity towards the enterobacterial flora and regulatory CD4+CD25- T cells are present in both conventional and germ-free mice. The data suggest that a significant proportion of the peripheral pool of CD4+CD25- T cells express anti-enterobacterial reactivity, which, due to the presence of regulatory CD4+CD25+ T cells, is kept in a quiescent state.

Lactobacillus plantarum 299: beneficial in vitro immunomodulation in cells extracted from inflamed human colon

BACKGROUND AND AIM

The present study determined the pattern of cytokine secretion (interleukin [IL]-1beta, tumor necrosis factor [TNF]-alpha, interferon [IFN]-gamma and IL-10) and their cellular sources in mononuclear cells isolated from colonic mucosa from normal and ulcerative colitis (UC) in response to probiotic and pathogenic bacteria.

METHODS

Mononuclear cells were extracted from normal and active UC colonic mucosa and incubated with pure sonicates of probiotic, commensal, and pathogenic bacteria. Cytokine secretion was measured in culture supernatant and intracellular cytokine staining measured using fluorescent-activated cytometry.

RESULTS

In mononuclear cells isolated from normal mucosa, significant increases in mean IL-1beta were observed with enteropathogenic Escherichia coli (286.3 +/- 138.7 pg/mL P < 0.05) and E. coli (440.5 +/- 194.0 pg/mL P < 0.01) compared with unstimulated control cells (16.7 +/- 4.8 pg/mL). In contrast, mononuclear cells isolated from active UC mucosa produced significant increases in mean IL-1beta in response to stimulation with Salmonella dublin (230.5 +/- 38.8 pg/mL P < 0.05), enteropathogenic E. coli (231.7 +/- 45.3 pg/mL P < 0.05) and E. coli (465.4 +/- 60.2 pg/mL P < 0.001) compared with unstimulated control cells (60.7 +/- 17.1 pg/mL). Escherichia coli also produced significant mean increases of TNF-alpha and IFN-gamma compared with unstimulated control cells. No significant increases in IL-1beta, TNF-alpha or IFN-gamma were observed with Lactobacillus plantarum in cells derived from normal or inflamed mucosa. Strikingly, incubation of L. plantarum with mononuclear cells isolated from active UC mucosa resulted in significant increases of mean IL-10 (327 +/- 53.5 pg/mL, P < 0.05) compared with unstimulated control cells (29.7 +/- 13.2 pg/mL). Intracellular cytokine staining confirmed T-cell and macrophage IL-10 production after L. plantarum stimulation.

CONCLUSIONS

Lactobacillus plantarum demonstrates beneficial immunomodulatory activity by increasing IL-10 synthesis and secretion in macrophages and T-cells derived from the inflamed colon. This may provide a mechanism through which probiotic bacteria ameliorate inappropriate inflammation and induce tolerance.

Effect of Interleukin-10 Null Mutation on Maternal Immune Response and Reproductive Outcome in Mice1

Interleukin-10 (IL-10) is an anti-inflammatory and immune-deviating cytokine expressed in the endometrium and placenta. IL-10 null mutant (IL-10-/-) mice have been employed to examine the role of IL-10 in regulating immune events in early pregnancy and its significance in implantation and pregnancy success. The inflammatory response elicited in endometrial tissue by insemination was amplified in IL-10-/- mice, with a 66% increase in leukocytes in the endometrial stroma on Day 3 of pregnancy. Despite this, no evidence of abnormal type 1/type 2 skewing was seen in T-lymphocytes from lymph nodes draining the uterus. On Day 18 of gestation, IL-10-/- females mated with IL-10-/- males had 15% more implantation sites and 27% more viable fetuses than pregnant wild-type (IL-10+/+) mice. Placental weight was unaffected, but fetal weight and the fetal:placental weight ratio were higher in IL-10-/- pregnancies. Similar data were obtained in allogeneic pregnancies when IL-10-/- females were mated with major-histocompatibility complex (MHC) disparate IL-10-/- males. Pups delivered by IL-10-/- mothers had increased birth weight and followed an altered growth trajectory, with growth impairment evident from early postnatal life into adulthood, which was reflected in alterations in body composition at 14 wk of age. This study shows that although IL-10 is not essential for maternal immune tolerance or successful pregnancy irrespective of MHC disparity in the fetus, maternal IL-10 is a determinant of growth trajectory in progeny in utero and after birth.

Engineered lymphocytes to treat dinitrobenzene sulphonic acid colitis in mice

Current treatments of inflammatory bowel diseases are limited either by their lack of efficacy or their potential toxicity. In recent years, major advances have been obtained by the development of biological therapies. However, these types of treatment are systemic and can lead to serious adverse events. The new venue of local biological treatments would be most welcome. In this issue of the Journal, Castagliuolo et al. show that lymphocytes engineered to produce TGF-beta1 can reverse dinitrobenzene sulphonic acid-induced colitis in mice. These engineered lymphocytes selectively accumulate in the intestinal mucosa due to the homing properties of their alpha4beta7 integrins, a ligand for MAdCAM1. A local treatment restricted to the inflamed mucosa can thus be obtained. This opens a brand new area of research with the hope of restoring the immunoregulatory balance selectively in the inflamed tissues.

Parenchymal organ, and not splenic, immunity correlates with host survival during disseminated candidiasis

We examined the relationship between host survival and renal and splenic immune responses in a murine model of hematogenously disseminated candidiasis. Male BALB/c mice were infected via tail vein injection with wild-type C. albicans or with an isogenic, Deltaefg1/Deltaefg1 hypha-deficient mutant. Host survival, organ fungal burden, intracellular cytokine content of splenic and kidney lymphocytes, and whole-organ cytokine profiles were determined. Wild-type C. albicans induced type 2 splenocyte responses with both nonfatal and fatal inocula. In the kidney, conversely, wild-type inocula causing no or low mortality induced type 1 responses and 100% fatal inocula induced type 2 or interleukin-10 (IL-10)-dominant responses. Hypha-deficient mutant C. albicans caused no or low mortality while inducing type 1 responses in both the spleen and kidney. To our knowledge, this is the first demonstration that host survival during systemic infection correlates with the type of immune response engendered in a nonlymphoid, parenchymal organ and not with the response in the spleen. Furthermore, the results provide in vivo confirmation that hyphal formation by C. albicans induces type 2 or IL-10-dominant host responses in tissues.

Phenotypic and functional characterization of long-term cultured rhesus macaque spleen-derived NKT cells

Natural killer T cells are immunoregulatory cells, which have important roles in tolerance and autoimmunity, as demonstrated primarily in mice and humans. In this study, we define the phenotype and function of Valpha24(+) T cells derived from the spleens of rhesus macaques, a species increasingly used in models of immune tolerance. Valpha24(+) cells were isolated and expanded with monocyte-derived immature dendritic cells in the presence of alpha-galactosylceramide, IL-2, and IL-15. Rhesus NKT cells were stained with mAbs against both Valpha24 and the invariant complementarity-determining region 3 epitope of the human Valpha24/JalphaQ TCR. The cells were CD4, CD8 double negative and expressed CD56. Rhesus NKT cells also exhibited moderate to high expression of CD95, CD45RO, CD11a, and beta(7) integrin, but did not express CD45 RA, CD62L, CCR7, CD28, and other activation, costimulatory molecules (CD69 and CD40L). By intracellular staining, >90% of unstimulated rhesus NKT cells expressed IL-10, but not IFN-gamma. However, the latter was strongly expressed after stimulation. Rhesus NKT secreted large amounts of TGF-beta, IL-13, and IL-6, and modest levels of IFN-gamma, whereas IL-10 secretion was negligible and no detectable IL-4 was observed either intracellularly or in culture supernatants. Functionally, the NKT cells and their supernatants suppressed T cell proliferation in allogeneic MLR. We conclude that long-term cultured rhesus macaque spleen-derived Valpha24(+) T cells are semi-invariant double-negative cells with effector memory phenotype. These cells are semianergic, polarized to a uniquely Th3 > T regulatory-1 regulatory cell phenotype, and have regulatory/suppressive function in vitro.

T cell activation, from atopy to asthma: more a paradox than a paradigm

During the last 15 years, it was largely shown that allergic inflammation was orchestrated by activated Th2 lymphocytes, leading to IgE production and eosinophil activation. Indeed, Th2 activation was shown to be necessary to induce allergic sensitization in animal models. In humans, a Th2 skewing was shown in atopic children soon after birth. In asthma, descriptive studies showed that Th2 cells were more numerous in patients than in controls. In addition, during specific allergen stimulation, an increase of Th2 cells was described in most cases. According to this Th2 paradigm, it was proposed that early avoidance of microbial exposure could explain the increase of atopic diseases seen in the last 20 years in developed countries, as the "hygiene hypothesis". Recently, it was proposed that early exposure to lipopolysaccharide (LPS) could be protective against atopic diseases. However, it is well established that exposure to LPS can induce asthma symptoms, both in animals and humans, although it induces a Th1 inflammatory response. In addition, most infections induce asthma exacerbations and Th1 responses. Recently, some studies have showed that some Th1 cells were present in asthmatic patients, which could be related to bronchial hyperreactivity. There is therefore an "infectious paradox" in asthma, which contributes to show that the Th2 paradigm is insufficient to explain the whole inflammatory reaction of this disease. We propose that the Th2paradigm is relevant to atopy and inception of asthma albeit a Th1 activation would account at least in part for bronchial hyperreactivity and asthma symptoms.

Chronic T cell-mediated enteropathy in rural west African children: relationship with nutritional status and small bowel function

Previous studies from The Gambia have shown that poor childhood growth is resistant to all but the most intense nutritional intervention and highly dependent on small bowel permeability related to enteropathy. We thus aimed to characterize the mucosal inflammatory response in rural Gambian children in relation to intestinal permeability and nutritional status. Small bowel biopsies were taken from 38 rural Gambian children (age, 0.5-3 y) with a range of nutritional and clinical states (median weight z score, -4.6; range, 0.5 to -6.4), 75% of whom had diarrhea. Morphometry was performed with immunohistochemical analysis for a range of lineage and activation markers, including proinflammatory and regulatory cytokines, and related to current clinical status and gut permeability. Comparison was made with 19 age-matched U.K. controls. All Gambian children, regardless of nutritional status, had evidence of chronic cell-mediated enteropathy with crypt hyperplasia, villous stunting, and high numbers of intraepithelial lymphocytes. CD25+ cells were 20-fold higher than in U.K. controls. Although small bowel architecture was independent of nutritional status, T cell numbers rose and B cell numbers fell with worsening nutrition, and mucosal cytokine production became biased toward a proinflammatory response, with progressive decrease of transforming growth factor-beta expression. Tropical enteropathy predates the onset of marasmus and is characterized by a cell-mediated TH1 response. Protein-energy malnutrition is associated with reduction of regulatory immune responses in the mucosal microenvironment, potentially impairing the mechanisms of oral tolerance.

Interleukin-4 and transforming growth factor beta have opposing regulatory effects on gamma interferon-mediated inhibition of Cryptosporidium parvum reproduction

It was shown previously that enterocytes activated by gamma interferon (IFN-gamma) are efficient effector cells in the killing of Cryptosporidium parvum. How this function is regulated is not clearly understood, but transforming growth factor beta (TGF-beta) and the Th2 regulatory cytokines may play a role. Using an in vitro cell culture system, we investigated how the key regulatory cytokines interleukin-4 (IL-4), IL-10, IL-13, and TGF-beta might modulate the effect of IFN-gamma in inducing resistance to infection in enterocyte cell lines. The results showed that TGF-beta can abolish the inhibitory effect on C. parvum development and that neither IL-13 nor IL-10 influenced the action of IFN-gamma. In contrast, IL-4 cooperated with low concentrations of IFN-gamma (1 and 10 U/ml) to enhance parasite killing. One mechanism that appeared to be involved in the combined activity of IFN-gamma and IL-4 was intracellular Fe(2+) deprivation, but induction of nitric oxide production was not involved. In one cell line, the extents and durations of phosphorylation of STAT1, a transcription factor involved in IFN-gamma signaling, were similar when cells were stimulated with IFN-gamma alone and with IFN-gamma and IL-4 gamma, suggesting that the cooperative effect of the cytokines was not related to STAT1 activation. The effects of the presence of TGF-beta and IL-4 on IFN-gamma function did not appear to involve any alteration in the level of expression of IFN-gamma receptors.

Gene transfer approaches for the treatment of inflammatory bowel disease

The pathogenesis of Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease, involves a complex interplay between certain genetic, environmental and immunological factors. Considerable research progress in the last decade defined key inflammatory pathways in the inflamed gut and identified new potential therapeutic targets. Since the current medical treatment with corticosteroids and anti-inflammatory drugs is often associated with undesired side effects and cannot completely cure IBD, these current advances in our understanding of intestinal pathology may now allow the development of new biologic treatment strategies including gene therapy. In this review, we will give a brief overview of potential gene therapy target molecules related to chronic intestinal inflammation. Furthermore, we summarize the results of recent preclinical studies for intestinal gene transfer and discuss future perspectives.

Parasite-specific immunomodulatory functions of filarial cystatin

Cystatins of parasitic nematodes are well-described pathogenicity factors which contribute to downregulation of T-cell proliferation of their hosts and induce anti-inflammatory cytokine responses. We compared the immunomodulatory effects of two cystatins of the filarial nematodes Onchocerca volvulus and Acanthocheilonema viteae with two homologous proteins of the free-living nematode Caenorhabditis elegans. Like filarial cystatins, the C. elegans cystatins (rCysele1 and rCysele2) possessed domains relevant for inhibition of papain-like proteases and were biologically active inhibitors of human cathepsins B, L, and S. However, the inhibition of cathepsin B by C. elegans cystatin was much stronger. C. elegans cystatins lacked a domain involved in inhibition of legumain-like proteases that was present in O. volvulus cystatin. Filarial cystatins suppressed the proliferation of human peripheral blood mononuclear cells (PBMC) and murine spleen cells, while the C. elegans cystatins had this effect to a much lesser extent. Whereas filarial cystatins markedly increased the production of interleukin (IL)-10, C. elegans cystatins increased the production of IL-12 and gamma interferon (IFN-gamma) by human PBMC. The cystatins of both the filariae and C. elegans induced an upregulation of inducible nitric oxide by IFN-gamma-stimulated murine macrophages. These data suggest that filarial cystatins but not the C. elegans cystatins downregulate proliferative responses of host cells due to characteristics which might reflect an adaptation of filariae to their parasitic life style.

Mucosal CD8alpha+ DC, with a plasmacytoid phenotype, induce differentiation and support function of T cells with regulatory properties

Repetitive stimulation of naïve T cells by immature splenic dendritic cells (DC) can result in the differentiation of T-cell lines with regulatory properties. In the present study we identified a population of DC in the mucosae that exhibit the plasmacytoid phenotype, secrete interferon-alpha (IFN-alpha) following stimulation with oligodeoxynucleotides containing certain cytosine-phosphate-guanosine (CpG) motifs and can differentiate naïve T cells into cells that exhibit regulatory properties. Although these DC appear to be present in both spleen and mesenteric lymph nodes (MLN), only CpG-matured DC from the MLN (but not the spleen) were able to differentiate naïve T cells into T regulatory 1-like cells with regulatory properties. The activity of these DC failed to sustain robust T-cell proliferation and thereby enhanced the suppressive efficacy of CD4+ CD25+ T regulatory cells. These DC are the major CD8alpha+ DC population in the Peyer's patches (PP). Given their significant presence in mucosal tissue, we propose that these DC may provide a mechanistic basis for the homeostatic regulation in the gut by eliciting regulatory cell suppressor function and poorly supporting T helper cell proliferation at a site of high antigenic stimulation like the intestine.

Emergence of perianal fistulizing disease in the SAMP1/YitFc mouse, a spontaneous model of chronic ileitis

BACKGROUND & AIMS

SAMP1/Yit mice spontaneously develop chronic terminal ileitis, reminiscent of the human disease described by Crohn et al. in 1932. Several new phenotypic features have appeared in our colony after more than 20 generations of brother-sister mating. In this report, we describe the distinguishing features of the SAMP1/YitFc substrain at the University of Virginia, compared with the Japanese SAMP1/Yit parental strain.

METHODS

A colony of SAMP1/Yit mice was established at the University of Virginia in 1996, from 2 breeding pairs obtained from Japan. A systematic characterization of their phenotypic and immunologic characteristics was performed at 4, 10, 40, and more than 60 weeks of age.

RESULTS

The following differences were observed: (1) SAMP1/YitFc mice displayed established ileitis as early as 10 weeks of age, (2) the incidence of skin lesions inversely correlated with the occurrence of intestinal inflammation, (3) mice develop chronic ileitis with prominent muscular hypertrophy and focal collagen deposition in inflamed segments, (4) mesenteric lymph node lymphocytes acquired an activated phenotype coincident with disease progression, (5) high interferon-gamma production was detected by 4 weeks of age and preceded the onset of ileitis, and (6) a subgroup of mice (approximately 5%) developed perianal disease with ulceration and fistulae.

CONCLUSIONS

The SAMP1/YitFc substrain exhibits unique characteristics when compared with the original Japanese strain. Of particular interest is the emergence of perianal fistulizing disease, to our knowledge the first report of such occurrence in an animal model of inflammatory bowel disease.

Activated/effector CD4+ T cells exacerbate acute damage in the central nervous system following traumatic injury

CD4(+) helper T cells (Th) have been demonstrated to participate in the chronic phase of traumatic injury repair in the central nervous system (CNS). Here, we show that CD4(+) T cells can also contribute to the severity of the acute phase of CNS traumatic injury. We compared the area of tissue damage and the level of cellular apoptosis in aseptic cerebral injury (ACI) sites of C57BL/6 wild type and RAG1(-/-) immunodeficient mice. We demonstrate that ACI is attenuated in RAG1(-/-) mice compared to C57BL/6 animals. Adoptive transfer of CD4(+)CD62L(low)CD44(high) activated/effector T cells 24 h prior to ACI into RAG1(-/-) mice resulted in a significantly enhanced acute ACI that was comparable to ACI in the C57BL/6 animals. Adoptive transfer of CD4(+)CD62L(high)CD44(low) naive/non-activated T cells did not increase ACI in the brains of RAG1(-/-) mice. T cell inhibitory agents, cyclosporin A (CsA) and FK506, significantly decreased ACI-induced acute damage in C57BL/6 mice. These results suggest a previously undescribed role for activated/effector CD4(+) T cells in exacerbating ACI-induced acute damage in the CNS and raise a novel possibility for acute treatment of sterile traumatic brain injury.

T cell regulation as a side effect of homeostasis and competition

We have previously hypothesized that maintaining a balanced peripheral immune system may not be the sole responsibility of a specialized subset of T cells dedicated to immune regulation, but also a side effect of normal competition for shared resources within an intact immune system. Here we show that regulatory activity is correlated with high homeostatic expansion potential, reflecting the avidity for self-peptide:MHC complexes. Monoclonal transgenic T cells with high homeostatic expansion potential and lacking characteristics previously associated with regulatory function were able to regulate wasting disease induced by transfer of a small number of naive CD45RB(hi) CD4 T cells into lymphopenic hosts. Self-regulatory function is also found in the naive polyclonal T cell repertoire depleted of CD25(+) T cells. T cells capable of preventing immune pathology, like the transgenic T cells, express higher than average levels of CD5, an indicator of avidity for self:MHC peptide complexes. We therefore propose that dysregulated expansion of potentially pathogenic T cells in a lymphopenic environment can be prevented by members of the naive T cell repertoire, irrespective of their specificity, as a side effect of their response to homeostatic and antigenic stimulation.

CD4+ CD25+ regulatory T lymphocytes inhibit microbially induced colon cancer in Rag2-deficient mice

Inflammatory bowel diseases, including ulcerative colitis and Crohn's disease, increase the risk of colorectal cancer in humans. It has been recently shown in humans and animal models that intestinal microbiota and host immunity are integral in the progression of large bowel diseases. Lymphocytes are widely believed to prevent bacterially induced inflammation in the bowel, and lymphocytes are also critical in protecting against primary tumors of intestinal epithelia in mice. Taken together, this raises the possibility that lymphocytes may inhibit colon carcinogenesis by reducing bacterially driven inflammation. To examine the role of bacteria, lymphocytes, and inflammatory bowel disease in the development of colon cancer, 129/SvEv Rag-2-deficient and congenic wild-type mice were orally inoculated with a widespread enteric mouse bacterial pathogen, Helicobacter hepaticus, or sham-dosed with media only. H. hepaticus-infected Rag2-/-, but not sham-dosed Rag2-/- mice, rapidly developed colitis and large bowel carcinoma. This demonstrated a link between microbially driven inflammation and cancer in the lower bowel and suggested that innate immune dysregulation may have an important role in inflammatory bowel disease and progression to cancer. H. hepaticus-infected wild-type mice did not develop inflammation or carcinoma showing that lymphocytes were required to prevent bacterially induced cancer at this site. Adoptive transfer with CD4+ CD45RBlo CD25+ regulatory T cells into Rag-deficient hosts significantly inhibited H. hepaticus-induced inflammation and development of cancer. These results suggested that the ability of CD4+ T cells to protect against intestinal cancer was correlated with their ability to reduce bacterially induced inflammatory bowel disease. Further, regulatory T cells may act directly on the innate immune system to reduce or prevent disease. These roles for T cells in protection against colon carcinoma may have implications for new modes of prevention and treatment of cancer in humans.

CD4+ T regulatory cells from the colonic lamina propria of normal mice inhibit proliferation of enterobacteria-reactive, disease-inducing Th1-cells from scid mice with colitis

Adoptive transfer of CD4+ T cells into scid mice leads to a chronic colitis in the recipients. The transferred CD4+ T cells accumulate in the intestinal lamina propria (LP), express an activated Th1 phenotype and proliferate vigorously when exposed ex vivo to enteric bacterial antigens. As LP CD4+ T cells from normal BALB/c mice do not respond to enteric bacterial antigens, we have investigated whether colonic LP-derived CD4+ T cells from normal mice suppress the antibacterial response of CD4+ T cells from scid mice with colitis. LP-derived CD4+ T cells cocultured with bone marrow-derived dendritic cells effectively suppress the antibacterial proliferative response of CD4+ T cells from scid mice with colitis. The majority of these LP T-reg cells display a nonactivated phenotype and suppression is independent of antigen exposure, is partly mediated by soluble factor(s) different from IL-10 and TGF-beta, and is not prevented by the addition of high doses of IL-2 to the assay culture. Functionally and phenotypically the T-reg cells of the present study differ from previously described subsets of T-reg cells. The presence of T cells with a regulatory potential in the normal colonic mucosa suggests a role for these cells in the maintenance of local immune homeostasis of the gut.