Vaccine-induced immunity against Helicobacter pylori infection is impaired in IL-18-deficient mice

Protective immunity against Helicobacter pylori infection in mice has been associated with a strong Th1 response, involving IL-12 as well as IFN-gamma, but recent studies have also demonstrated prominent eosinophilic infiltration, possibly linked to local Th2 activity in the gastric mucosa. In this study we investigated the role of IL-18, because this cytokine has been found to be a coregulator of Th1 development as well as involved in Th2-type responses with local eotaxin production that could influence gastric eosinophilia and resistance to infection. We found that IL-18(-/-) mice failed to develop protection after oral immunization with H. pylori lysate and cholera toxin adjuvant, indicating an important role of IL-18 in protection. Well-protected C57BL/6 wild-type (WT) mice demonstrated substantial influx of CD4(+) T cells and eosinophilic cells in the gastric mucosa, whereas IL-18(-/-) mice had less gastritis, few CD4(+) T cells, and significantly reduced numbers of eosinophilic cells. T cells in well-protected WT mice produced increased levels of IFN-gamma and IL-18 to recall Ag. By contrast, unprotected IL-18(-/-) mice exhibited significantly reduced gastric IFN-gamma and specific IgG2a Ab levels. Despite differences in gastric eosinophilic cell infiltration, protected WT and unprotected IL-18(-/-) mice had comparable levels of local eotaxin, suggesting that IL-18 influences protection via Th1 development and IFN-gamma production rather than through promoting local production of eotaxin and eosinophilic cell infiltration.     

Protection against Helicobacter pylori infection following immunization is IL-12-dependent and mediated by Th1 cells

The regulatory roles of Th1 and Th2 cells in immune protection against Helicobacter infection are not clearly understood. In this study, we report that a primary H. pylori infection can be established in the absence of IL-12 or IFN-gamma. However, IFN-gamma, but not IL-12, was involved in the development of gastritis because IFN-gamma(-/-) (GKO) mice exhibited significantly less inflammation as compared with IL-12(-/-) or wild-type (WT) mice. Both IL-12(-/-) and GKO mice failed to develop protection following oral immunization with H. pylori lysate and cholera toxin adjuvant. By contrast, Th2-deficient, IL-4(-/-), and WT mice were equally well protected. Mucosal immunization in the presence of coadministered rIL-12 in WT mice increased Ag-specific IFN-gamma-producing T cells by 5-fold and gave an additional 4-fold reduction in colonizing bacteria, confirming a key role of Th1 cells in protection. Importantly, only protected IL-4(-/-) and WT mice demonstrated substantial influx of CD4(+) T cells in the gastric mucosa. The extent of inflammation in challenged IL-12(-/-) and GKO mice was much reduced compared with that in WT mice, indicating that IFN-gamma/Th1 cells also play a major role in postimmunization gastritis. Of note, postimmunization gastritis in IL-4(-/-) mice was significantly milder than WT mice, despite a similar level of protection, indicating that immune protection is not directly linked to the degree of gastric inflammation. Only protected mice had T cells that produced high levels of IFN-gamma to recall Ag, whereas both protected and unprotected mice produced high levels of IL-13. We conclude that IL-12 and Th1 responses are crucial for H. pylori-specific protective immunity.     

Helicobacter pylori gastritis: a Th1 mediated disease?

Helicobacter pylori is now considered to be the main cause for most stomach diseases including ulcer, MALT lymphoma, adenocarcinoma and gastritis. The infection with this bacterium is chronic despite a local and systemic immune response towards it. Among the cellular infiltrate that arises during H. pylori-mediated gastritis, there is a considerable frequency of CD4+ Th1 cells producing IFNgamma, but not of Th2 cells producing IL-4. Since IFNgamma may induce binding of H. pylori to gastric epithelial cells followed by apoptosis of these cells, one may speculate that H. pylori-mediated diseases are in part autoimmune diseases initiated by H. pylori-specific Th1 cells infiltrating the gastric mucosa. Recent support for this hypothesis comes from an animal model in which mice are infected with H. pylori and display strongly reduced gastritis in the absence of IFNgamma.     

Helicobacter pylori-induced mucosal inflammation is Th1 mediated and exacerbated in IL-4, but not IFN-gamma, gene-deficient mice

To elucidate the pathogenesis of Helicobacter pylori-associated gastritis, we studied immune responses of C57BL/6J wild-type (WT), SCID, and gene deficient (IFN-gamma-/- and IL-4-/-) mice following infection with a pathogenic isolate of H. pylori (SPM326). During early infection in WT mice, mononuclear and polymorphonuclear cells accumulated in the gastric lamina propria, and the numbers of cells in the inflamed mucosa expressing IFN-gamma, but not IL-4, mRNA rose significantly (p < 0.005), consistent with a local Th1 response. Splenic T cells from the same infected WT mice produced high levels of IFN-gamma, no detectable IL-4, and low amounts of IL-10 following in vitro H. pylori urease stimulation, reflecting a systemic Th1 response. Infected C57BL/6J SCID mice did not develop gastric inflammation despite colonization by many bacteria. Infected C57BL/10J and BALB/c mice also did not develop gastric inflammation and displayed a mixed Th1/Th2 splenic cytokine profile. These data imply a major role for the Th1 cytokine IFN-gamma in H. pylori-associated gastric inflammation in C57BL/6J mice. Compared with WT animals, infected IL-4-/- animals had more severe gastritis and higher levels of IFN-gamma production by urease-stimulated splenocytes (p < 0.01), whereas IFN-gamma-/- mice exhibited no gastric inflammation and higher levels of IL-4 production by stimulated splenocytes. These findings establish C57BL/6J mice as an important model for H. pylori infection and demonstrate that up-regulated production of IFN-gamma, in the absence of the opposing effects of IL-4 (and possibly IL-10), plays a pivotal role in promoting H. pylori-induced mucosal inflammation.     

Helicobacter pylori, T cells and cytokines: the "dangerous liaisons"

Helicobacter pylori infection is the major cause of gastroduodenal pathologies, but only a minority of infected patients develop chronic and life threatening diseases, as peptic ulcer, gastric cancer, B-cell lymphoma, or autoimmune gastritis. The type of host immune response against H. pylori is crucial for the outcome of the infection. A predominant H. pylori-specific Th1 response, characterized by high IFN-gamma, TNF-alpha, and IL-12 production associates with peptic ulcer, whereas combined secretion of both Th1 and Th2 cytokines are present in uncomplicated gastritis. Gastric T cells from MALT lymphoma exhibit abnormal help for autologous B-cell proliferation and reduced perforin- and Fas-Fas ligand-mediated killing of B cells. In H. pylori-infected patients with autoimmune gastritis cytolytic T cells infiltrating the gastric mucosa cross-recognize different epitopes of H. pylori proteins and H+K+ ATPase autoantigen. These data suggest that peptic ulcer can be regarded as a Th1-driven immunopathological response to some H. pylori antigens, whereas deregulated and exhaustive H. pylori-induced T cell-dependent B-cell activation can support the onset of low-grade B-cell lymphoma. Alternatively, H. pylori infection may lead in some individuals to gastric autoimmunity via molecular mimicry.     

Cross-primed CD8+ cytotoxic T cells induce severe Helicobacter-associated gastritis in the absence of CD4+ T cells

BACKGROUND: Although previous studies have reported important roles of CD4(+) type 1-helper T cells and regulatory T cells in Helicobacter-associated gastritis, the significance of CD8(+) cytotoxic T cells remains unknown. To study the roles of CD8(+) T cells, we examined the immune response in the gastric mucosa of Helicobacter felis-infected major histocompatibility complex (MHC) class II-deficient (II(-/-)) mice, which lack CD4(+) T cells. MATERIALS AND METHODS: Stomachs from H. felis-infected wild-type and infected MHC II(-/-) mice were examined histologically and immunohistochemically. Gastric acidity and serum levels of anti-H. felis antibodies were measured. The expression of pro-inflammatory and anti-inflammatory cytokine, Fas-ligand, perforin, and Foxp3 genes in the gastric mucosa was investigated. RESULTS: H. felis-infected MHC II(-/-) mice developed severe gastritis, accompanied by marked infiltration of CD8(+) cells. At 1 and 2 months after inoculation, mucosal inflammation and atrophy were more severe in MHC II(-/-) mice, although gastritis had reached similar advanced stages at 3 months after inoculation. There was little infiltration of CD4(+) cells, and no Foxp3-positive cells were detected in the gastric mucosa of the infected MHC II(-/-) mice. The expression of the interleukin-1beta and Fas-ligand genes was up regulated, but that of Foxp3 was down regulated in the infected MHC II(-/-) mice. Serum levels of anti-H. felis antibodies were lower in the infected MHC II(-/-) mice, despite severe gastritis. CONCLUSIONS: The present study suggests that cross-primed CD8(+) cytotoxic T cells can induce severe H.-associated gastritis in the absence of CD4(+) helper T cells and that Foxp3-positive cells may have an important role in the control of gastric inflammation.     

CD5-CK2 binding/activation-deficient mice are resistant to experimental autoimmune encephalomyelitis: protection is associated with diminished populations of IL-17-expressing T cells in the central nervous system

Regulating the differentiation and persistence of encephalitogenic T cells is critical for the development of experimental autoimmune encephalomyelitis (EAE). We reported recently that CD5 has an engagement-dependent prosurvival activity in T cells that played a direct role in the induction and progression EAE. We predicted that CD5 regulates T cell apoptosis/survival through the activation of CK2, a prosurvival serine/threonine kinase that associates with the receptor. To test this hypothesis, we generated mice expressing CD5 with the inability to bind and activate CK2 and assessed their susceptibility to EAE. We found mice deficient in CD5-CK2 signaling pathway were mostly resistant to the development of EAE. Resistance to EAE was associated with a dramatic decrease in a population of effector infiltrating Th cells that coexpress IFN-gamma and IL-17 and, to a lesser extent, cells that express IFN-gamma or IL-17 in draining lymph nodes and spinal cords. We further show that T cells deficient in CD5-CK2 signaling hyperproliferate following primary stimulation; however, following restimulation, they rapidly develop nonresponsiveness and exhibit elevated activation-induced cell death. Our results provide a direct role for CD5-CK2 pathway in T cell activation and persistence of effector T cells in neuroinflammatory disease. This study predicts that targeting of IFN-gamma(+)/IL-17(+) infiltrating Th cells will be useful for the treatment of multiple sclerosis and other systemic autoimmune diseases.     

Intraperitoneal immunization led to T cell hyporesponsiveness to Helicobacter pylori infection in mice

During Helicobacter pylori infection, T cell response is critical in the development of active gastritis and in protective immunity against infection. We studied gastric inflammation and T cell response in H. pylori-challenged mice following an intraperitoneal immunization, using whole H. pylori lysate (HpAg) in the absence of adjuvants. H. pylori-challenged mice without immunization developed moderate to severe gastric inflammation, and splenocytes from these mice produced Th1 polarizing cytokines in response to HpAg and Con A during the acute infection. On the other hand, immunized-challenged mice (those inoculated with H. pylori following immunization) had little or no gastric inflammation despite persistent H. pylori colonization. Our immunization primed splenocytes to produce IL-2, IFN-gamma, and IL-4 in response to HpAg and Con A before infection. However, these cells became hyporesponsive to both stimulants immediately after live bacterial challenge in terms of the production of these cytokines, especially IL-2 and IFN-gamma. CTLA-4 has been documented to be a negative regulator of IL-2 production and lymphoproliferation that induces peripheral tolerance and functions 24-72 hr after the initiation of T cell activation. Compared with challenged mice, T cells from immunized-challenged mice showed higher levels of CTLA-4 expression at 72 hr after oral challenge. These data suggested that our immunization inhibited the development of H. pylori-associated gastritis and induced T cell hyporesponsiveness to H. pylori infection, which might be mediated by the early induction of CTLA-4 following challenge.     

IgA antibodies impair resistance against Helicobacter pylori infection: studies on immune evasion in IL-10-deficient mice

We recently reported that Helicobacter pylori-specific Abs impair the development of gastritis and down-regulate resistance against H. pylori infection. In this study, we asked whether IgA Abs specifically can have an impact on H. pylori colonization and gastric inflammation. To obtain a sensitive model for the study of inflammation we crossed IgA- and IL-10-deficient mice. We found that IL-10(-/-)/IgA(-/-) mice were significantly less colonized than IL-10(-/-)/IgA(+/+) mice, which in turn were less colonized than wild-type (WT) mice. The IL-10(-/-)/IgA(-/-) mice exhibited a 1.2-log reduction in bacterial counts compared with that in IL-10(-/-)/IgA(+/+) mice, suggesting that IgA Abs rather promoted than prevented infection. The reduced colonization in IL-10(-/-)/IgA(-/-) mice was associated with the most severe gastritis observed, albeit all IL-10(-/-) mice demonstrated more severe gastric inflammation than wild-type mice. The gastritis score and the infiltration of CD4(+) T cells into the gastric mucosa were significantly higher in IL-10(-/-)/IgA(-/-) mice than in IL-10(-/-)/IgA(+/+) mice, arguing that IgA Abs counteracted inflammation. Moreover, following oral immunization, IL-10(-/-)/IgA(-/-) mice were significantly better protected against colonization than IL-10(-/-)/IgA(+/+) mice. However, the stronger protection was associated with more severe postimmunization gastritis and gastric infiltration of CD4(+) T cells. There was also a clear increase in complement receptor-expressing cells in IL-10(-/-)/IgA(-/-) mice, though C3b-fragment deposition in the gastric mucosa was comparable between the two. Finally, specific T cell responses to recall Ag demonstrated higher levels of IFN-gamma production in IL-10(-/-)/IgA(-/-) as compared with IL-10(-/-)/IgA(+/+) mice. Thus, it appears that IgA and IL-10 help H. pylori bacteria evade host resistance against infection.     

Adoptive transfer of splenocytes in SCID mice implicates CD4+ T cells in apoptosis and epithelial proliferation associated with Helicobacter pylori-induced gastritis

Helicobacter pylori causes severe, rapidly progressive gastritis in severe combined immunodeficient (SCID) mouse recipients of congenic splenocytes. The H. pylori-infected and uninfected C57BL/6J and recipient SCID mice were evaluated to detect CD4+ and CD8+ T cells, B cells, apoptotic epithelial cells, and epithelial cell proliferation at postinoculation weeks 5, 6, 8, and 12. Serum was evaluated for anti-H. pylori IgG and IgM. In all H. pylori-infected mice, gastric CD4+ cell scores were increased, compared with scores for uninfected controls. Recipient mice differed, however, according to the source of the transferred CD4+ cells. The CD4+ cell scores for recipients of splenocytes from H. pylori-infected (immune) donors were indistinguishable from those for wild-type donor mice at all time points. In contrast, gastric mucosal CD4+ cell scores did not become significantly high until two weeks after transfer (postinoculation week 6) in recipients of cells from uninfected (na?ve) donors. Gastric epithelial apoptosis and the gastric epithelial proliferation zone were significantly (P < 0.05) increased in infected recipient and donor, compared with non-recipient and uninfected mice at postinoculation week 12. Results indicated that CD4 cells are sensitized in vivo and migrate to the gastric mucosa where they induce gastritis in response to H. pylori antigens. Influx of CD4 cells and gastritis are correlated with epithelial proliferation and apoptosis, and suggest that CD4-dependent H. pylori gastritis leads to epithelial damage with attendant proliferative and metaplastic responses.     

The role of T cell subsets and cytokines in the pathogenesis of Helicobacter pylori gastritis in mice

Gastritis due to Helicobacter pylori in mice and humans is considered a Th1-mediated disease, but the specific cell subsets and cytokines involved are still not well understood. The goal of this study was to investigate the immunopathogenesis of H. pylori-induced gastritis and delayed-type hypersensitivity (DTH) in mice. C57BL/6-Prkdc(scid) mice were infected with H. pylori and reconstituted with CD4+, CD4-depleted, CD4+CD45RB(high), or CD4+CD45RB(low) splenocytes from wild-type C57BL/6 mice or with splenocytes from C57BL/6(IFN-gamma-/-) or C57BL/6(IL-10-/-) mice. Four or eight weeks after transfer, DTH to H. pylori Ags was determined by footpad injection; gastritis and bacterial colonization were quantified; and IFN-gamma secretion by splenocytes in response to H. pylori Ag was determined. Gastritis and DTH were present in recipients of unfractionated splenocytes, CD4+ splenocytes, and CD4+CD45RB(high) splenocytes, but absent in the other groups. IFN-gamma secretion in response to H. pylori Ags was correlated with gastritis, although splenocytes from all groups of mice secreted some IFN-gamma. Gastritis was most severe in recipients of splenocytes from IL-10-deficient mice, and least severe in those given IFN-gamma-deficient splenocytes. Bacterial colonization in all groups was inversely correlated with gastritis. These data indicate that 1) CD4+ T cells are both necessary and sufficient for gastritis and DTH due to H. pylori in mice; 2) high expression of CD45RB is a marker for gastritis-inducing CD4+ cells; and 3) IFN-gamma contributes to gastritis and IL-10 suppresses it, but IFN-gamma secretion alone is not sufficient to induce gastritis. The results support the assertion that H. pylori is mediated by a Th1-biased cellular immune response.     

Virus-specific memory and effector T lymphocytes exhibit different cytokine responses to antigens during experimental murine respiratory syncytial virus infection.

Mice sensitized to the G (attachment) or F (fusion) glycoproteins of respiratory syncytial virus (RSV) expressed different patterns of cytokine production and lung pathology when challenged by intranasal infection with RSV. Five days after challenge, mice sensitized to G glycoprotein produced high levels of interleukin-4 (IL-4) and IL-5 in the lungs and spleens and developed extensive pulmonary eosinophilia, while mice sensitized to F glycoprotein produced IL-2 and developed a mononuclear cell infiltration. Memory lymphocytes isolated 2 weeks after intranasal challenge of mice primed to the G or F glycoprotein secreted only IL-2 and gamma interferon (IFN-gamma) when stimulated with RSV. IL-4 and IL-5 production characteristic of Th2-type effectors in the lung was observed only after multiple rounds of in vitro stimulation of RSV G-specific memory T lymphocytes with antigen. Also IFN-gamma production appeared to play only a minor role in the expression of pulmonary pathology characteristic of Th1 or Th2 T-lymphocyte responses, because mice genetically deficient in IFN-gamma production by gene disruption displayed the same pattern of pulmonary inflammation to RSV infection after priming to RSV F or G as conventional mice. These results suggest that effector T lymphocytes exhibit a different pattern of cytokine production than memory T-lymphocyte precursors precommitted to a Th1 or Th2 pattern of differentiation. Furthermore, these observations raise the possibility that the cytokine response of human memory T lymphocytes after a single exposure to antigen in vitro may not accurately reflect the cytokine response of differentiated effector T lymphocytes at the site of infection in vivo.     

In vivo generation of pathogen-specific Th1 cells in the absence of the IFN-gamma receptor

The precise mechanisms that govern the commitment of CD4 T cells to become Th1 or Th2 cells in vivo are incompletely understood. Recent experiments demonstrate colocalization of the IFN-gammaR chains with the TCR during activation of naive CD4 T cells, suggesting that association of these molecules may be involved in determining lineage commitment. To test the role of IFN-gamma and its receptor in the generation of Th1 Ag-specific CD4 T cells, we analyzed mice after infection with Listeria monocytogenes or lymphocytic choriomeningitis virus. In the absence of IFN-gamma, Ag-specific CD4 T cells were generated in response to both these infections. In addition, IFN-gamma-producing (Th1) Ag-specific CD4 T cells were generated in mice lacking the ligand-binding chain of the IFN-gammaR (IFN-gammaR1-/-) or the signaling chain (IFN-gammaR2-/-). There was no increase in the number of IL-4-producing Ag-specific CD4 T cells, nor was there a decrease in the expression of T-bet in the absence of functional IFN-gamma signaling, indicating that the cells were committed Th1 cells. Thus, both chains of the IFN-gammaR are dispensable for the generation of Th1 Ag-specific CD4 T cells after infection in vivo.     

Dual roles for IFN-gamma,but not for IL-4, in spontaneous autoimmune thyroiditis in NOD.H-2h4 mice

Spontaneous autoimmune thyroiditis (SAT) is an organ-specific autoimmune disease characterized by chronic inflammation of the thyroid by T and B lymphocytes. To investigate the roles of Th1 and Th2 cytokines in the pathogenesis of SAT, IFN-gamma(-/-) and IL-4(-/-) NOD.H-2h4 mice were generated. IL-4(-/-) mice developed lymphocytic SAT (L-SAT) comparable to that of wild-type (WT) mice. They produced little anti-mouse thyroglobulin (MTg) IgG1, but had levels of anti-MTg IgG2b comparable to WT mice. Compared with WT mice, IFN-gamma(-/-) mice produced significantly less anti-MTg IgG1 and IgG2b. Absence of IFN-gamma resulted in abnormal proliferation of thyroid epithelial cells with minimal lymphocyte infiltration. Thyroids of IFN-gamma(-/-) mice had markedly reduced B lymphocyte chemoattractant expression, B cell and plasma cell infiltration, and decreased MHC class II expression on thyrocytes compared with WT mice. Adoptive transfer of WT splenocytes to IFN-gamma(-/-) mice restored the capacity to develop typical L-SAT, enhanced anti-MTg IgG1 and IgG2b production, up-regulated MHC class II expression on thyrocytes and decreased thyrocyte proliferation. These results suggest that IFN-gamma plays a dual role in the development of SAT. IFN-gamma is required for development of L-SAT, and it also functions to inhibit thyroid epithelial cell proliferation.     

IL-12 administration accelerates autoimmune diabetes in both wild-type and IFN-gamma-deficient nonobese diabetic mice,revealing pathogenic and protective effects of IL-12-induced IFN-gamma

IL-12 administration to nonobese diabetic (NOD) mice induces IFN-gamma-secreting type 1 T cells and high circulating IFN-gamma levels and accelerates insulin-dependent diabetes mellitus (IDDM). Here we show that IL-12-induced IFN-gamma production is dispensable for diabetes acceleration, because exogenous IL-12 could enhance IDDM development in IFN-gamma-deficient as well as in IFN-gamma-sufficient NOD mice. Both in IFN-gamma(+/-) and IFN-gamma(-/-) NOD mice, IL-12 administration generates a massive and destructive insulitis characterized by T cells, macrophages, and CD11c(+) dendritic cells, and increases the number of pancreatic CD4(+) cells secreting IL-2 and TNF-alpha. Surprisingly, IL-12-induced IFN-gamma hinders pancreatic B cell infiltration and inhibits the capacity of APCs to activate T cells. Although pancreatic CD4(+) T cells from IL-12-treated IFN-gamma(-/-) mice fail to up-regulate the P-selectin ligand, suggesting that their entry into the pancreas may be impaired, T cell expansion is favored in these mice compared with IL-12-treated IFN-gamma(+/-) mice because IL-12 administration in the absence of IFN-gamma leads to enhanced cell proliferation and reduced T cell apoptosis. NO, an effector molecule in beta cell destruction, is produced ex vivo in high quantity by pancreas-infiltrating cells through a mechanism involving IL-12-induced IFN-gamma. Conversely, in IL-12-treated IFN-gamma-deficient mice, other pathways of beta cell death appear to be increased, as indicated by the up-regulated expression of Fas ligand on Th1 cells in the absence of IFN-gamma. These data demonstrate that IFN-gamma has a dual role, pathogenic and protective, in IDDM development, and its deletion allows IL-12 to establish alternative pathways leading to diabetes acceleration.     

Loss of STAT3 in CD4+ T cells prevents development of experimental autoimmune diseases

Th17 cells are implicated in CNS autoimmune diseases. We show that mice with targeted-deletion of Stat3 in CD4(+) T cells (CD4(Stat3)(-/-)) do not develop experimental autoimmune uveoretinitis (EAU) or experimental autoimmune encephalomyelitis. Defective Th17 differentiation noted in CD4(Stat3)(-/-) mice is compensated by exaggerated increases in Foxp3-, IL-10-, IL-4-, and IFN-gamma-expressing T cells, suggesting critical roles of STAT3 in shaping Ag-specific CD4(+) T cell repertoire. In mice with EAU, a high percentage of IL-17-expressing T cells in their peripheral lymphoid organs also secrete IFN-gamma while these double-expressors are absent in CD4(Stat3)(-/-) and wild-type mice without EAU, raising the intriguing possibility that uveitis maybe mediated by Th17 and IL-17-expressing Th1 cells. Resistance of Stat3-deficient mice to EAU derives in part from an inability of uveitogenic Th17 and Th1 cells to enter eyes or brain of the CD4(Stat3)(-/-) mouse because of the reduction in the expression of activated alpha4/beta1 integrins on CD4(Stat3)(-/-) T cells. Adoptive transfer of activated interphotoreceptor retinoid-binding protein-specific uveitogenic T cells induced in CD4(Stat3)(-/-) mice a severe EAU characterized by development of retinal folds, infiltration of inflammatory cells into the retina, and destruction of retinal architecture, underscoring our contention that the loss of STAT3 in CD4(+) T cells results in an intrinsic developmental defect that renders CD4(Stat3)(-/-) resistant to CNS inflammatory diseases. STAT3 requirement for IL-17 production by Th17, generation of double positive T cells expressing IL-17 and IFN-gamma, and for T cell trafficking into CNS tissues suggests that STAT3 may be a therapeutic target for modulating uveitis, sceritis, or multiple sclerosis.     

Increased susceptibility to autoimmune gastritis in thymic stromal lymphopoietin receptor-deficient mice

Thymic stromal lymphopoietin (TSLP), mainly produced by epithelial cells, activates a variety of cell types, including dendritic cells, mast cells, T cells, and B cells. It is involved in the pathogenesis of allergic inflammation in the lung, skin, and gastrointestinal tract. In addition, TSLP promotes Th2-type intestinal immunity against helminth infection and regulates Th1-type inflammation in a mouse model of colitis, suggesting that it plays crucial roles in intestinal immune homeostasis. Although autoimmune gastritis (AIG), mediated by inflammatory Th1 responses, develops in the gastric mucosa, it is not clear whether TSLP is involved in regulating these responses in AIG. The aim of this study was to examine the roles of TSLP in the development of AIG. Because BALB/c mice thymectomized 3 d after birth (NTx mice) develop AIG, we used this model to test the role of TSLP in the development of AIG. We found that in AIG-bearing mice, TSLP was expressed in the inflamed stomach and that the serum anti-parietal cell Ab levels in neonatal thymectomized TSLPR-deficient mice (NTx-TSLPR(-/-) mice) were significantly elevated over those in NTx-TSLPR(+/+) mice. In addition, NTx-TSLPR(-/-) mice exhibited an earlier onset of AIG than that observed in NTx-TSLPR(+/+) mice. The rapid development of AIG in NTx-TSLPR(-/-) mice resulted in more aggressive CD4(+) T cell infiltration and more severe loss of parietal and chief cells in the progression phase of AIG, accompanied by enhanced production of IL-12/23p40 and IFN-γ. Taken together, these data suggested that TSLP negatively regulates the development of AIG.     

Synergistic effect of IL-2, IL-12, and IL-18 on thymocyte apoptosis and Th1/Th2 cytokine expression

In the periphery, IL-18 synergistically induces the expression of the Th1 cytokine IFN-gamma in the presence of IL-12 and the Th2 cytokines IL-5 and IL-13 in the presence of IL-2. Although the expression of these cytokines has been described in the thymus, their role in thymic development and function remains uncertain. We report here that freshly isolated thymocytes from C57BL/6 and BALB/c mice stimulated in vitro with IL-2-plus-IL-18 or IL-12-plus-IL-18 produce large amounts of IFN-gamma and IL-13. Analysis of the thymic subsets, CD4(-)CD8(-) (DN), CD4(+)CD8(+), CD4(+)CD8(-), and CD4(-)CD8(+) revealed that IL-18 in combination with IL-2 or IL-12 induces IFN-gamma and IL-13 preferentially from DN cells. Moreover, DN2 and DN3 thymocytes contained more IFN-gamma(+) cells than cells in the later stage of maturation. Additionally, IL-18 in combination with IL-2 induces CCR4 (Th2-associated) and CCR5 (Th1-associated) gene expression. In contrast, IL-18-plus-IL-12 specifically induced CCR5 expression. The IL-2-plus-IL-18 or IL-12-plus-IL-18 effect on IFN-gamma and IL-13 expression is dependent on Stat4 and NF-kappaB but independent of Stat6, T-bet, or NFAT. Furthermore, IL-12-plus-IL-18 induces significant thymocyte apoptosis when expressed in vivo or in vitro, and this effect is exacerbated in the absence of IFN-gamma. IL-12-plus-IL-18-stimulated thymocytes can also induce IA-IE expression on cortical and medullary thymic epithelial cells in an IFN-gamma-dependent manner. Thus, the combination of IL-2, IL-12, and IL-18 can induce phenotypic and functional changes in thymocytes that may alter migration, differentiation, and cell death of immature T cells inside the thymus and potentially affect the Th1/Th2 bias in peripheral immune compartments.