Pathogenic Th2-type follicular helper T cells contribute to the development of lupus in Fas-deficient mice.

Fas mutant mice are well recognized as autoimmune mouse models, which develop symptoms similar to human systemic lupus erythematosus. Although disease severity in Fas mutant mice is greatly affected by the genetic background, the mechanisms affecting pathological heterogeneity among different strains of Fas mutant mice are poorly understood. In this study, we examined the phenotypic differences between Fas-deficient (Fas (-/-)) mice on the BALB/c and C57BL/6 backgrounds to gain insight into the etiological and pathological heterogeneity of monogenic autoimmune diseases. Fas (-/-) mice on the BALB/c background (BALB/c-Fas (-/-)) developed more severe autoimmune disease with high serum auto-antibodies and renal disease compared with those on the C57BL/6 background (C57BL/6-Fas (-/-)). Splenic B cells were highly activated, and germinal center formation was enhanced in BALB/c-Fas (-/-) but not in C57BL/6-Fas (-/-) mice. Follicular helper T (Tfh) cells were equally abundant in the spleens from both strains of Fas (-/-) mice. However, Tfh cells from BALB/c-Fas (-/-) mice produced much higher amounts of B-cell-activating cytokines, including IL-4 and IL-10, a phenotype reminiscent of Th2-type Tfh cells described in human studies. Our results revealed a qualitative difference in Tfh cells between the two strains of Fas (-/-) mice. We propose that the pathogenic Th2-type Tfh cells in BALB/c-Fas (-/-) mice contribute to the excessive activation of B cells, resulting in high serum immunoglobulin levels and the severe lupus phenotype, which may account for the differential outcomes of human monogenic autoimmune diseases.

Identification of a novel type 2 innate immunocyte with the ability to enhance IgE production.

Fas (CD95), a member of the tumor necrosis factor receptor superfamily, mediates apoptosis-inducing signals in its expressing cells, especially in self-reactive cells. We recently reported that Fas(-/-) mice with a BALB/c background (BALB/c Fas(-/-) mice) developed blepharitis with allergic inflammation that was accompanied by hyper-IgE production. Here, we found a novel type of immunocyte in the spleen of BALB/c Fas(-/-) mice, which enhanced the production of IgE by B cells in the presence of IL-4 and CD40 signaling in vitro. The immunocyte did not express lineage markers but expressed Thy-1 and Sca-1 just like recently identified type 2 innate lymphoid cells, such as natural helper (NH) cells and nuocytes. However, they did not express c-Kit, IL-7R and IL-33R (T1/ST2), important markers of type 2 innate lymphoid cells. Instead, our identified Lin(-)Thy-1(+)Sca-1(+) cells expressed IL-18R and secreted Th2 cytokines when co-cultured with B cells or when stimulated with IL-18 and IL-2. Moreover, we found essentially the same type of cells in BALB/c wild-type mice as in BALB/c Fas(-/-) mice, which enhanced IgE production in contact with B cells in vitro. These cells from BALB/c wild-type mice expressed Fas and were sensitive to Fas-mediated apoptosis. Collectively, the newly identified Lin(-)Thy-1(+)Sca-1(+) cell, which we designated a F-NH cell (Fas-expressing natural helper cell), is a novel type 2 innate immunocyte with activity to enhance IgE production from B cells with the help of IL-4 and CD40 signaling. F-NH cells may play an important role in the development of chronic allergic inflammation.

Fas deficiency in mice with the Balb/c background induces blepharitis with allergic inflammation and hyper-IgE production in conjunction with severe autoimmune disease.

Fas (CD95) is a cell surface death receptor belonging to the tumor necrosis factor receptor superfamily, which mediates apoptosis-inducing signaling when activated by Fas ligand or its agonistic antibody. lpr mice with a loss of apoptosis-inducing function mutation in the Fas gene develop systemic autoimmune disease and lymphadenopathy but not allergic inflammation. In the case of Fas mutations including lpr and knockout (KO), background genes determine the incidence and severity of lymphadenopathy and histopathological manifestation of systemic autoimmunity: MRL-lpr/lpr mice and C57BL/6-lpr/lpr or C57BL/6 Fas KO mice develop severe and minimum disease, respectively. We generated Fas KO mice with the Balb/c background that show severer autoimmune phenotypes than MRL-lpr/lpr mice, such as critical infiltration of mononuclear cells into lung, liver and spleen, elevated serum levels of auto-antibodies and a decreased life span. To our astonishment, Balb/c Fas KO mice spontaneously develop blepharitis with not only autoimmune inflammation with deposition of auto-antibody but also allergic inflammation with infiltration by eosinophils and mast cells and show the capacity to strongly increase serum level of IgE and IgG1 along with their aging. Thus, Fas expression regulates development of not only autoimmune disease but also allergic inflammation.

A critical role of IL-33 in experimental allergic rhinitis.

BACKGROUND: We reported previously that serum levels of IL-33 are significantly increased in patients with allergic rhinitis (AR). However, very little is known about the role of IL-33 for the development of AR. OBJECTIVE: We thought to develop a novel murine model of ragweed pollen-specific AR and examined the pathologic role for ragweed-induced IL-33 in the development of AR manifestation using IL-33-deficient (il33(-/-)) mice. METHODS: Ragweed-immunized and ragweed-challenged mice were examined for early- and late-phase nasal responses. IL-33 protein expression in the nasal epithelial cells of the AR murine model and patients with AR were assessed by using confocal microscopy. RESULTS: After nasal challenge with ragweed pollen, ragweed-immunized wild-type mice manifested early-phase (sneezing) and late-phase (eosinophilic and basophilic accumulation) responses. In contrast, il33(-/-) and FcεRI(-/-) mice did not have both early- and late-phase AR responses. IL-33 protein was constitutively expressed in the nucleus of nasal epithelial cells and was promptly released into nasal fluids in response to nasal exposure to ragweed pollen. In human subjects we revealed constitutive expression of IL-33 protein in the nasal epithelial cells of healthy control subjects and downregulated expression of IL-33 protein in inflamed nasal epithelial cells of patients with AR. IL-33-stimulated mast cells and basophils contributed to the early- and late-phase AR manifestation through increasing histamine release and production of chemoattractants for eosinophils/basophils, respectively. CONCLUSIONS: Ragweed pollen-driven endogenous IL-33 contributed to the development of AR responses. IL-33 might present an important therapeutic target for the prevention of AR.

Contribution of IL-33-activated type II innate lymphoid cells to pulmonary eosinophilia in intestinal nematode-infected mice.

When animals are infected with helminthic parasites, resistant hosts show type II helper T immune responses to expel worms. Recently, natural helper (NH) cells or nuocytes, newly identified type II innate lymphoid cells, are shown to express ST2 (IL-33 receptor) and produce IL-5 and IL-13 when stimulated with IL-33. Here we show the relevant roles of endogenous IL-33 for Strongyloides venezuelensis infection-induced lung eosinophilic inflammation by using Il33(-/-) mice. Alveolar epithelial type II cells (ATII) express IL-33 in their nucleus. Infection with S. venezuelensis or intranasal administration of chitin increases in the number of ATII cells and the level of IL-33. S. venezuelensis infection induces pulmonary accumulation of NH cells, which, after being stimulated with IL-33, proliferate and produce IL-5 and IL-13. Furthermore, S. venezuelensis infected Rag2(-/-) mice increase the number of ATII cells, NH cells, and eosinophils and the expression of IL-33 in their lungs. Finally, IL-33-stimulated NH cells induce lung eosinophilic inflammation and might aid to expel infected worms in the lungs.

Crucial role of impaired Kupffer cell phagocytosis on the decreased Sonazoid-enhanced echogenicity in a liver of a nonalchoholic steatohepatitis rat model.

AIMS: To evaluate the dynamics of Kupffer cell (KC) phagocytosis by performing both in vivo and in vitro studies using Sonazoid (GE Healthcare, Oslo) in a rat nonalcoholic steatohepatitis (NASH) model. METHODS: Contrast enhanced ultrasonography (CEUS) was performed on a rat NASH model induced by a methionine choline deficient diet (MCDD) and control rats, and Sonazoid was used to measure the signal intensity in the liver parenchyma. The uptake of Sonazoid by the KCs was observed by intravital microscopy. Their phagocytic capability was evaluated in vitro using isolated and cultured KCs. The uptake of fluorescein isothiocyanate (FITC)-labeled latex beads was observed and quantitatively analyzed by flow cytometry. RESULTS: In the MCDD group, liver parenchymal enhancement was reduced 20 min after the Sonazoid injection. Microscopic observation of the isolated and cultured KCs revealed that the number of phagocytosed Sonazoid microbubbles was significantly decreased. Confocal laser scanning microscopic (CLSM) observation showed a decrease in the uptake of the latex beads. A decreased phagocytic capacity in the MCDD group was suggested by the quantitative analysis using flow cytometry, as well as by intravital microscopy. CONCLUSIONS: CEUS with Sonazoid is a powerful evaluation tool to diagnose NASH from an early stage of the disease.

Contribution of IL-33 to induction and augmentation of experimental allergic conjunctivitis.

IL-33, a member of the IL-1 family of cytokines, is the ligand for ST2 (IL-33Ralpha chain). IL-33 has the capacity to induce T(h)2 cytokine production from T(h)2 cells, mast cells and basophils, indicating that IL-33 has the potential to induce T(h)2 cytokine-mediated allergic inflammation of the eye. Thus, we tested the pathological role of IL-33 in allergic conjunctivitis (AC). As reported elsewhere, animals immunized with ragweed pollen (RW)/alum and boosted with RW/PBS developed AC promptly (within 15 min) and conjunctival eosinophilic inflammation after a delay (within 24 h) in response to eye drop challenge with RW. Furthermore, RW-immunized mice, when topically challenged with both RW and IL-33, developed more striking eosinophilia in their conjunctiva without exacerbation of the clinical AC score. This in vivo IL-33 treatment significantly increased the capacity of T cells in the cervical lymph nodes of RW-immunized mice to produce IL-4, IL-5 and IL-13 upon challenge with anti-CD3 and anti-CD28 antibodies in vitro. Furthermore, the infiltrating cells were largely eosinophils and a small proportion of CD4(+) T cells, both of which express ST2. We also found that even splenic eosinophils express ST2 and show increased expression in response to IL-5, granulocyte-macrophage colony-stimulating factor (GM-CSF) or IL-33. Eosinophils, stimulated with IL-5 and/or GM-CSF, are responsive to IL-33, which induces production of IL-4 and chemokines. Finally, we showed that conjunctival tissues constitutively express biologically active IL-33, suggesting that IL-33 might play a crucial role in the induction and augmentation of AC.

Administration of IL-33 induces airway hyperresponsiveness and goblet cell hyperplasia in the lungs in the absence of adaptive immune system.

Systemic administration of IL-18 induces polyclonal IgE responses by causing NKT cells to express CD40 ligand and to produce IL-4. Administration of IL-33 also induces IgE response, although the mechanism underlying IgE response is unclear. Here, we compared the effects of IL-18 and IL-33 on bone marrow-derived mast cells and basophils as well as non-polarized and T(h)2-polarized CD4(+) T cells in vitro. Basophils, comprising IL-18Ralpha(+) cells (14.2%) and IL-33Ralpha(+) cells (34.6%), and mast cells, comprising IL-18Ralpha(+) cells (2.0%) and IL-33Ralpha(+) cells (95.6%), produce IL-4, IL-6, IL-13, granulocyte macrophage colony-stimulating factor (GM-CSF) and chemokines (RANTES, MIP-1alpha, MIP-1beta and MCP-1), upon stimulation with IL-18 and/or IL-33 in the presence of IL-3. Only basophils strongly produce IL-4. Furthermore, compared with mast cells, basophils produce larger amounts of the above cytokines and chemokines in response to IL-33. Level of IL-33Rbeta-mRNA expression in basophils is higher than that in mast cells. Effect of IL-33 is dependent on ST2 binding, and its signal is transduced via MyD88 in vitro. We also found that IL-2 plus IL-18 or IL-33 alone stimulates non-polarized or T(h)2-polarized CD4(+) T cells to produce IL-4 and IL-13 or IL-5 and IL-13, respectively. We finally showed that administration of IL-33 into mice ST2/MyD88 dependently induces airway hyperresponsiveness (AHR) and goblet cell hyperplasia by induction of IL-4, IL-5 and IL-13 in the lungs. Furthermore, same treatment of RAG-2(-/-) mice, lacking T and B cells, more strikingly induced AHR with marked goblet cell hyperplasia and eosinophilic infiltration in the lungs. Thus, IL-33 induces asthma-like symptom entirely independent of acquired immune system.

Critical roles of myeloid differentiation factor 88-dependent proinflammatory cytokine release in early phase clearance of Listeria monocytogenes in mice.

Listeria monocytogenes (LM), a facultative intracellular Gram-positive bacterium, often causes lethal infection of the host. In this study we investigated the molecular mechanism underlying LM eradication in the early phase of infection. Upon infection with LM, both IL-12 and IL-18 were produced, and then they synergistically induced IFN-gamma production, leading to normal LM clearance in the host. IFN-gamma knockout (KO) mice were highly susceptible to LM infection. IL-12/IL-18 double knockout mice were also highly susceptible. Their susceptibility was less than that of IFN-gamma KO mice, but more than that of single IL-12 or IL-18 KO mice. Mice deficient in myeloid differentiation factor 88 (MyD88), an essential adaptor molecule used by signal transduction pathways of all members of the Toll-like receptor (TLR) family, showed an inability to produce IL-12 and IFN-gamma following LM infection and were most susceptible to LM. Furthermore, MyD88-deficient, but not IFN-gamma-deficient, Kupffer cells could not produce TNF-alpha in response to LM in vitro, indicating the importance of MyD88-dependent TNF-alpha production for host defense. As TLR2 KO, but not TLR4 KO, mice showed partial impairment in their capacity to produce IL-12, IFN-gamma, and TNF-alpha, TLR2 activation partly contributed to the induction of IL-12-mediated IFN-gamma production. These results indicated a critical role for TLRs/MyD88-dependent IL-12/TNF-alpha production and for IL-12- and IL-18-mediated IFN-gamma production in early phase clearance of LM.