Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by type 2 immune responses. Interleukin-25 (IL-25) is produced predominantly by epithelial cells. It can activate Th2 cells to produce type 2 cytokines such as IL-4, IL-5 and IL-13, contributing to host defense against nematodes. However, excessive/inappropriate production of IL-25 is considered to be involved in development of type 2 cytokine-associated allergic disorders such as asthma. On the other hand, the contribution of IL-25 to the pathogenesis of AD remains poorly understood. In the present study, we found that expression of Il25 mRNA was significantly increased in the skin of mice during oxazolone-induced chronic contact hypersensitivity (CHS), which is a mouse model of human AD. In addition, development of oxazoloneinduced chronic CHS was significantly reduced in IL-25-deficient (Il25-/-) mice compared with wildtype mice on the C57BL/6, but not BALB/c, background, although IL-25 was not essential for IL-4 production by hapten-specific T cells. Therefore, IL-25 is crucial for development of chronic CHS, although that is partly dependent on the genetic background of the mice.(c) 2022 Elsevier Inc. All rights reserved.

TitleA mouse model of asthma­–chronic obstructive pulmonary disease overlap induced by intratracheal papain

Background: In addition to thymic stromal lymphopoietin and IL-33, IL-25 is known to induce T(H)2 cytokine production by various cell types, including T(H)2 cells, T(H)9 cells, invariant natural killer T cells, and group 2 innate lymphoid cells, involved in T(H)2-type immune responses. Because both T(H)2-type and T(H)17-type cells/cytokines are crucial for contact hypersensitivity (CHS), IL-25 can contribute to this by enhancing T(H)2-type immune responses. However, the precise role of IL-25 in the pathogenesis of fluorescein isothiocyanate-induced CHS is poorly understood. Objective: We investigated the contribution of IL-25 to CHS using Il25(-/-) mice. Methods: CHS was evaluated by means of measurement of ear skin thickness in mice after fluorescein isothiocyanate painting. Skin dendritic cell (DC) migration, hapten-specific T-H cell differentiation, and detection of IL-1 beta-producing cells were determined by using flow cytometry, ELISA, and immunohistochemistry, respectively. Results: In contrast to thymic stromal lymphopoietin, we found that IL-25 was not essential for skin DC migration or hapten-specific T-H cell differentiation in the sensitization phase of CHS. Unexpectedly, mast cell-and non-immune cell-derived IL-25 was important for hapten-specific T(H)17 cell-mediated rather than T(H)2 cell-mediated inflammation in the elicitation phase of CHS by enhancing T(H)17-related, but not T(H)2-related, cytokines in the skin. In particular, IL-1 beta produced by dermal DCs in response to IL-25 was crucial for hapten-specific T(H)17 cell activation, contributing to induction of local inflammation in the elicitation phase of CHS. Conclusion: Our results identify a novel IL-25 inflammatory pathway involved in induction of T(H)17 cell-mediated, but not T(H)2 cell-mediated, CHS. IL-25 neutralization can be a potential approach for treatment of CHS.

IL-17C, which is a member of the IL-17 family of cytokines, is preferentially produced by epithelial cells in the lung, skin and colon, suggesting that IL-17C may be involved in not only host defense but also inflammatory diseases in those tissues. In support of that, IL-17C was demonstrated to contribute to development of T cell-dependent imiquimod-induced psoriatic dermatitis and T cell-independent dextran sodium sulfate-induced acute colitis using mice deficient in IL-17C and/or IL-17RE, which is a component of the receptor for IL-17C. However, the roles of IL-17C in other inflammatory diseases remain poorly understood. Therefore, we investigated the contributions of IL-17C to development of certain disease models using Il17c −/− mice, which we newly generated. Those mice showed normal development of T cell-dependent inflammatory diseases such as FITC- and DNFB-induced contact dermatitis/contact hypersensitivity (CHS) and concanavalin A-induced hepatitis, and T cell-independent inflammatory diseases such as bleomycin-induced pulmonary fibrosis, papain-induced airway eosinophilia and LPS-induced airway neutrophilia. On the other hand, those mice were highly resistant to LPS-induced endotoxin shock, indicating that IL-17C is crucial for protection against that immunological reaction. Therefore, IL-17C neutralization may represent a novel therapeutic approach for sepsis, in addition to psoriasis and acute colitis.

Certain proteases derived from house dust mites and plants are considered to trigger initiation of allergic airway inflammation by disrupting tight junctions between epithelial cells. It is known that inhalation of proteases such as house dust mite-derived Der p1 and/or papaya-derived papain caused airway eosinophilia in naïve mice and even in Rag-deficient mice that lack acquired immune cells such as T, B and NKT cells. In contrast, little is known regarding the possible involvement of proteases derived from Aspergillus species (fungal-associated proteases; FAP), which are ubiquitous saprophytic fungi in the environment, in the development of allergic airway eosinophilia. Here, we found that inhalation of FAP by naïve mice led to airway eosinophilia that was dependent on protease-activated receptor-2 (PAR2), but not TLR2 and TLR4. Those findings suggest that the protease activity of FAP, but not endotoxins in FAP, are important in the setting. In addition, development of that eosinophilia was mediated by innate immune cells (ILCs) such as innate lymphoid cells, but not by acquired immune cells such as T, B and NKT cells. Whereas IL-33, IL-25 and thymic stromal lymphopoietin (TSLP) are involved in induction of FAP-induced ILC-mediated airway eosinophilia, IL-33-rather than IL-25 and/or TSLP-was critical for the eosinophilia in our model. Our findings improve our understanding of the molecular mechanisms involved in induction of airway inflammation by FAP.

Appropriate immune responses and mucosal barrier functions are required for the maintenance of intestinal homeostasis. Defects in this defense system may lead to inflammatory disorders such as inflammatory bowel disease. Downstream of tyrosine kinases 1 (Dok-1) and its closest homolog, Dok-2, are preferentially expressed in immune cells, and play essential roles in the negative regulation of multiple signaling pathways in both innate and adaptive immunity. However, the function of these proteins in intestinal homeostasis remained unclear. Here we show that Dok-1/-2 double knockout (DKO) mice were highly susceptible to dextran sodium sulfate (DSS)-induced colitis compared with Dok-1 or Dok-2 single KO and wild type (WT) mice. Furthermore, DSS-treated Dok-1/-2 DKO mice exhibited increased colonic tissue damage accompanied by reduced proliferation of the epithelial cells relative to WT controls, suggesting that Dok-1/-2 DKO mice have defects in the repair of intestinal epithelial lesions. In addition, the levels of the Th17 cytokines IL-17A and IL-22, which have protective roles in DSS-induced colitis, were reduced in DSS-treated Dok-1/-2 DKO mice compared with WT mice. Taken together, our results demonstrate that Dok-1 and Dok-2 negatively regulate intestinal inflammation, apparently through the induction of IL-17A and IL-22 expression.

IL-25, IL-33 and TSLP, which are produced predominantly by epithelial cells, can induce production of Th2-type cytokines such as IL-4, IL-5 and/or IL-13 by various types of cells, suggesting their involvement in induction of Th2-type cytokine-associated immune responses. It is known that Th2-type cytokines contribute to host defense against malaria parasite infection in mice. However, the roles of IL-25, IL-33 and TSLP in malaria parasite infection remain unclear. Thus, to elucidate this, we infected wild-type, IL-25−/−, IL-33−/− and TSLP receptor (TSLPR)−/− mice with Plasmodium berghei (P. berghei) ANKA, a murine malaria strain. The expression levels of IL-25, IL-33 and TSLP mRNA were changed in the brain, liver, lung and spleen of wild-type mice after infection, suggesting that these cytokines are involved in host defense against P. berghei ANKA. However, the incidence of parasitemia and survival in the mutant mice were comparable to in the wild-type mice. These findings indicate that IL-25, IL-33 and TSLP are not critical for host defense against P. berghei ANKA.

IL-17RA is a shared receptor subunit for several cytokines of the IL-17 family, including IL-17A, IL-17C, IL-17E (also called IL-25) and IL-17F. It has been shown that mice deficient in IL-17RA are more susceptible to sepsis than wild-type mice, suggesting that IL-17RA is important for host defense against sepsis. However, it is unclear which ligands for IL-17RA, such as IL-17A, IL-17C, IL-17E/IL-25 and/or IL-17F, are involved in the pathogenesis of sepsis. Therefore, we examined IL-17A, IL-17E/IL-25 and IL-17F for possible involvement in LPS-induced endotoxin shock. IL-17A-deficient mice, but not IL-25- or IL-17F-deficient mice, were resistant to LPS-induced endotoxin shock, as compared with wild-type mice. Nevertheless, studies using IL-6-deficient, IL-21Rα-deficient and Rag-2-deficient mice, revealed that neither IL-6 and IL-21, both of which are important for Th17 cell differentiation, nor Th17 cells were essential for the development of LPS-induced endotoxin shock, suggesting that IL-17A-producing cells other than Th17 cells were important in the setting. In this connection, IL-17A was produced by macrophages, DCs and eosinophils after LPS injection. Taken together, these findings indicate that IL-17A, but not IL-17F or IL-25, is crucial for LPS-induced endotoxin shock. In addition, macrophages, DCs and eosinophils, but not Th17 cells or γδ T cells, may be sources of IL-17A during LPS-induced endotoxin shock.

IL-17, which is preferentially produced by Th17 cells, is important for host defense against pathogens and is also involved in the development of autoimmune and allergic disorders. Antibody (Ab) production was shown to be impaired in IL-17-deficient mice, suggesting that IL-17 may promote B cell activation and direct secretion of Ab. However, the precise role of IL-17 in Ab production by B cells remains unclear. In the present study, we found constitutive expression of IL-17R in murine splenic B cells. Nevertheless, IL-17, IL-17F or IL-25 alone could not induce Ab production by B cells even in the presence of agonistic anti-CD40 Ab. IL-17 also could not affect IFN-gamma-, IL-4- or TGF-beta 1-mediated Ig class-switching. Furthermore, in co-cultures of B cells and IL-17(-/-) CD4(+) T cells or IL-17(-/-) Th17 cells, IL-17 deficiency did not influence Ab production by B cells in vitro, suggesting that Th17 cell-derived IL-17 was not required for B cell Ab production through T cell-B cell interaction in vitro. Thus, in vivo, IL-17 may be indirectly involved in Ab production by enhancing production of B cell activator(s) by other immune cells. (C) 2012 Elsevier Ltd. All rights reserved.

IL-17A, IL-17F, and IL-25 are ligands for IL-17RA. In the current study, we demonstrated that IL-25–deficient mice—but not IL-17A–, IL-17F–, IL-17A/F–, IL-23p19–, or retinoic acid-related orphan receptor (ROR)-γt–deficient mice—showed significant suppression of 1) the number of eosinophils and the levels of proinflammatory mediators in bronchoalveolar lavage fluids, 2) airway hyperresponsiveness to methacholine, and 3) OVA-specific IgG1 and IgE levels in the serum during OVA-induced Th2-type/eosinophilic airway inflammation. The IL-25 deficiency did not affect lung dendritic cell migration or Ag-specific memory–Th2 cell expansion during Ag sensitization. Adoptive transfer of T cells, mast cells, or bone marrow cells from IL-25–deficient mice revealed that induction of Th2-type/eosinophilic airway inflammation was dependent on activation of lung epithelial cells and eosinophils by IL-25 produced by airway structural cells such as epithelial cells but not by such hematopoietic stem-cell-origin immune cells as T cells and mast cells. Therefore, airway structural cell-derived IL-25—rather than Th17 cell-derived IL-17A and IL-17F—is responsible for induction of local inflammation by promoting activation of lung epithelial cells and eosinophils in the elicitation phase of Th2-type/eosinophilic airway inflammation. It is not required for Ag-specific Th2 cell differentiation in the sensitization phase.

Background— Interleukin-17 (IL-17), which is predominantly produced by T helper 17 cells distinct from T helper 1 or T helper 2 cells, participates in the pathogenesis of infectious, autoimmune, and allergic disorders. However, the precise role in allograft rejection remains uncertain. In the present study, we investigated the role of IL-17 in acute allograft rejection using IL-17-deficient mice. Methods and Results— Donor hearts from FVB mice were heterotopically transplanted into either C57BL/6J-IL-17-deficient (IL-17−/−) or -wild-type mice. Allograft survival was significantly prolonged in IL-17−/− recipient mice due to reduced local inflammation accompanied by decreased inflammatory cell recruitment and cytokine/chemokine expression. IL-17−/− recipient mice exhibited decreased IL-6 production and reciprocally enhanced regulatory T cell expansion, suggesting a contribution of regulatory T cells to prolonged allograft survival. Indeed, allografts transplanted into anti-CD25 mAb-treated IL-17−/− recipient mice (regulatory T cell-depleted) developed acute rejection similar to wild-type recipient mice. Surprisingly, we found that gamma delta T cells rather than CD4+ and CD8+ T cells were key IL-17 producers in the allografts. In support, equivalent allograft rejection was observed in Rag-2−/− recipient mice engrafted with either wild-type or IL-17−/− CD4+ and CD8+ T cells. Finally, hearts transplanted into gamma delta T cell-deficient mice resulted in decreased allograft rejection compared with wild-type controls. Conclusions— During heart transplantation, (1) IL-17 is crucial for acceleration of acute rejection; (2) IL-17-deficiency enhances regulatory T cell expansion; and (3) gamma delta T cells rather than CD4+ and CD8+ T cells are a potential source of IL-17. IL-17 neutralization may provide a potential target for novel therapeutic treatment for cardiac allograft rejection.

BACKGROUND:β-1,6-N-acetylglucosaminyltransferase V (Mgat5 or GlcNac-TV), which is involved in the glycosylation of proteins, is known to be important for down-regulation of TCR-mediated T-cell activation and negatively regulates induction of contact dermatitis and experimental autoimmune encephalomyelitis. However, the role of Mgat5 in the induction of allergic airway inflammation remains unclear.METHODS:To elucidate the role of Mgat5 in the pathogenesis of allergic airway inflammation, ovalbumin (OVA)-induced airway inflammation was induced in Mgat5-deficient mice. The OVA-specific lymphocyte proliferation and cytokine production levels, OVA-specific IgG1, IgG2a and IgE levels in the serum, and the number of leukocytes and cytokine levels in the bronchoalveolar lavage (BAL) fluid were compared between wild-type and Mgat5-deficient mice.RESULTS:OVA-specific lymphocyte proliferation and production of IFN-γ and IL-10, but not IL-4, were increased in Mgat5-deficient mice, suggesting that Th2-type immune responses are seemed to be suppressed by increased IFN-γ and IL-10 production in these mice. However, Th2-type responses such as OVA-specific IgG1, but not IgE, and IL-5 levels in BAL fluids were increased in Mgat5-deficient mice. Meanwhile, the number of eosinophils was normal, but the numbers of neutrophils, macrophages and lymphocytes were reduced, in these mutant mice during OVA-induced airway inflammation.CONCLUSIONS:Mgat5-dependent glycosylation of proteins can modulate acquired immune responses, but it is not essential for the development of OVA-induced eosinophilic airway inflammation.

Hyperplasia associated with a loss of tissue homeostasis can induce DNA replication stress, leading to precancerous dysregulation. Epidermal gammadelta T cells reside in the primary barrier that protects against diverse environmental insults; however, the functions of these T cells in tissue surveillance are not completely understood. In mice with inducible Notch1 inactivation in keratinocytes that causes epidermal hyperplasia, epidermal gammadelta T cells sensed stressed keratinocytes and migrated into the cutaneous draining lymph nodes. Simultaneous induction of beta-galactosidase (beta-Gal) as a putative antigen expressed in the process of precancerous dysregulation and Notch1 ablation in the epidermis resulted in elevated beta-Gal-specific IgG2a production. Epidermal gammadelta T cells were found to have the capacity to express chemokine (C-C motif) receptor 7 and migrate into the lymph nodes. Cutaneous draining lymph node cells in Notch1-inactivated mice expressed high levels of IFN-gamma upon anti-CD3 plus anti-CD28 stimulation. Furthermore, induced expression of beta-Gal in mice that lacked epidermal gammadelta T cells failed to induce anti-beta-Gal IgG. These results suggest that epidermal gammadelta T cells play an essential role in the initiation process of epidermal antigen-specific humoral immune responses and demonstrate the importance of epidermal gammadelta T cells in sensing precancerous dysregulation and activating adaptive immunity.