Lack of functional TSLP receptors mitigates Th2 polarization and the establishment and growth of 4T1 primary breast tumours but has different effects on tumour quantities in the lung and brain

The 4T1 mammary carcinoma cell line produces TSLP. We had hypothesized that TSLP promotes the development of a permissive environment for the growth and metastasis of primary tumour and that this is associated with a Th2-polarized antitumour immune response. We found that, in Tslpr(-/-) mice, the mean tumour diameters were smaller from days 27 to 40, and relatively fewer tumour cells were present in the lung, compared with wild-type mice. Polarization of the Th2 cytokine profile was also diminished in Tslpr(-/-) mice. These findings confirmed those reported previously by others. Here, we further show that primary tumours are established less often in Tslpr(-/-) mice and that, unexpectedly, the relative number of tumour cells in the brain is greater in Tslpr(-/-) mice compared with wild-type mice. Findings from our cytotoxicity assays show that 4T1-directed lysis is undetectable in both WT and Tslpr(-/-) mice, ruling out the possibility that altered cytotoxic responses in Tslpr(-/-) mice are responsible for the differences we observed. In a human tissue microarray, positive staining for TSLP was seen in tumour cells from breast cancer tissue, but it was also seen in normal glandular epithelial cells from normal breast tissue, which has not been shown before. Thus, our findings provide new insight into the effects of TSLP in metastatic breast cancer.

Local BLyS production by T follicular cells mediates retention of high affinity B cells during affinity maturation

BLyS expression by GC follicular T cells is required for the efficient selection of high-affinity GC B cells.

We have assessed the role of B lymphocyte stimulator (BLyS) and its receptors in the germinal center (GC) reaction and affinity maturation. Despite ample BLyS retention on B cells in follicular (FO) regions, the GC microenvironment lacks substantial BLyS. This reflects IL-21–mediated down-regulation of the BLyS receptor TACI (transmembrane activator and calcium modulator and cyclophilin ligand interactor) on GC B cells, thus limiting their capacity for BLyS binding and retention. Within the GC, FO helper T cells (T_FH cells) provide a local source of BLyS. Whereas T cell–derived BLyS is dispensable for normal GC cellularity and somatic hypermutation, it is required for the efficient selection of high affinity GC B cell clones. These findings suggest that during affinity maturation, high affinity clones rely on T_FH-derived BLyS for their persistence.

Induction of thymic stromal lymphopoietin production by nonanoic acid and exacerbation of allergic inflammation in mice

BACKGROUND

Thymic stromal lymphopoietin (TSLP) plays critical roles in the induction and exacerbation of allergic diseases. We tested various chemicals in the environment and found that xylene and 1,2,4-trimethylbenzene induced the production of TSLP in vivo. These findings prompted us to search for additional chemicals that induce TSLP production. In this study, we examined whether fatty acids could induce the production of TSLP in vivo and exacerbate allergic inflammation.

METHODS

Various fatty acids and related compounds were painted on the ear lobes of mice and the amount of TSLP in the homogenate of ear lobe tissue was determined. The effects of nonanoic acid on allergic inflammation were also examined.

RESULTS

Octanoic acid, nonanoic acid, and decanoic acid markedly induced TSLP production, while a medium-chain aldehyde and alcohol showed only weak activity. Nonanoic acid induced the production of TSLP with a maximum at 24 h. TSLP production was even observed in nonanoic acid-treated C3H/HeJ mice that lacked functional toll-like receptor 4. The aryl hydrocarbon receptor agonist β-naphthoflavone did not induce TSLP production. Nonanoic acid promoted sensitization to ovalbumin, resulting in an enhancement in the cutaneous anaphylactic response. In addition, painting of nonanoic acid after the sensitization augmented picryl chloride-induced thickening of the ear, which was reversed in TSLP receptor-deficient mice.

CONCLUSIONS

Nonanoic acid and certain fatty acids induced TSLP production, resulting in the exacerbation of allergic inflammation. We propose that TSLP-inducing chemical compounds such as nonanoic acid be recognized as chemical allergo-accelerators.

IL-21 restricts virus-driven Treg cell expansion in chronic LCMV infection

Foxp3⁺ regulatory T (Treg) cells are essential for the maintenance of immune homeostasis and tolerance. During viral infections, Treg cells can limit the immunopathology resulting from excessive inflammation, yet potentially inhibit effective antiviral T cell responses and promote virus persistence. We report here that the fast-replicating LCMV strain Docile triggers a massive expansion of the Treg population that directly correlates with the size of the virus inoculum and its tendency to establish a chronic, persistent infection. This Treg cell proliferation was greatly enhanced in IL-21R^−/− mice and depletion of Treg cells partially rescued defective CD8⁺ T cell cytokine responses and improved viral clearance in some but not all organs. Notably, IL-21 inhibited Treg cell expansion in a cell intrinsic manner. Moreover, experimental augmentation of Treg cells driven by injection of IL-2/anti-IL-2 immune complexes drastically impaired the functionality of the antiviral T cell response and impeded virus clearance. As a consequence, mice became highly susceptible to chronic infection following exposure to low virus doses. These findings reveal virus-driven Treg cell proliferation as potential evasion strategy that facilitates T cell exhaustion and virus persistence. Furthermore, they suggest that besides its primary function as a direct survival signal for antiviral CD8⁺ T cells during chronic infections, IL-21 may also indirectly promote CD8⁺ T cell poly-functionality by restricting the suppressive activity of infection-induced Treg cells.

T cell exhaustion represents a state of T cell dysfunction associated with clinically relevant diseases, such as persistent viral infections or cancer. Although the molecular signature of exhausted T cells has been characterized in detail at the functional and transcriptional level, the immunological mechanisms that lead to T cell exhaustion during chronic infections remain poorly understood. Our present study reports two major findings that illustrate a pathway that contributes to T cell exhaustion during viral infection, and indicate its modulation by both, the pathogen and the host. First, we show that a persistence-inducing virus triggers the massive proliferation of Foxp3⁺ regulatory T (Treg) cells and demonstrate the potential of Treg cells to promote T cell exhaustion and chronic infection. Second, we identify IL-21 as a crucial host factor that antagonizes this virus-driven expansion of the Treg population in a cell intrinsic manner independent of IL-2. Thus, in addition to its known pre-dominant direct positive effects on antiviral T cells, IL-21 can also alleviate the suppressive activity of Treg cells. Together, these results suggest enhanced Treg cell responses as a mechanism of immune evasion that could be therapeutically targeted with IL-21.

Interleukin-2 at the crossroads of effector responses, tolerance, and immunotherapy

Interleukin-2 (IL-2) is a pleiotropic cytokine produced after antigen activation that plays pivotal roles in the immune response. Discovered as a T cell growth factor, IL-2 additionally promotes CD8(+) T cell and natural killer cell cytolytic activity and modulates T cell differentiation programs in response to antigen, promoting naïve CD4(+) T cell differentiation into T helper 1 (Th1) and T helper 2 (Th2) cells while inhibiting T helper 17 (Th17) and T follicular helper (Tfh) cell differentiation. Moreover, IL-2 is essential for the development and maintenance of T regulatory cells and for activation-induced cell death, thereby mediating tolerance and limiting inappropriate immune reactions. In this review, we focus on the molecular mechanisms and complex cellular actions of IL-2, its cooperative and opposing effects with other cytokines, and how both promoting and blocking the actions of IL-2 are being utilized in clinical medicine.

The cytokines IL-21 and GM-CSF have opposing regulatory roles in the apoptosis of conventional dendritic cells

Interleukin-21 (IL-21) has broad actions on T and B cells, but its actions in innate immunity are poorly understood. Here we show that IL-21 induced apoptosis of conventional dendritic cells (cDCs) via STAT3 and Bim, and this was inhibited by granulocyte-macrophage colony-stimulating factor (GM-CSF). ChIP-Seq analysis revealed genome-wide binding competition between GM-CSF-induced STAT5 and IL-21-induced STAT3. Expression of IL-21 in vivo decreased cDC numbers, and this was prevented by GM-CSF. Moreover, repetitive α-galactosylceramide injection of mice induced IL-21 but decreased GM-CSF production by natural killer T (NKT) cells, correlating with decreased cDC numbers. Furthermore, adoptive transfer of wild-type CD4+ T cells caused more severe colitis with increased DCs and interferon-γ (IFN-γ)-producing CD4+ T cells in Il21r(-/-)Rag2(-/-) mice (which lack T cells and have IL-21-unresponsive DCs) than in Rag2(-/-) mice. Thus, IL-21 and GM-CSF exhibit cross-regulatory actions on gene regulation and apoptosis, regulating cDC numbers and thereby the magnitude of the immune response.

A profibrotic role for thymic stromal lymphopoietin in systemic sclerosis

OBJECTIVE

[corrected] Systemic sclerosis (SSc) is an autoimmune disease characterised by progressive fibrosis. Although SSc shares pathogenetic features with other autoimmune diseases, the participation of profibrotic Th2 cytokines is unique to SSc, but the mechanisms of Th2 skewing are unknown. We have analysed the expression and function of thymic stromal lymphopoietin (TSLP), a central regulator of Th2-mediated allergic inflammation, in human SSc, primary lung fibrosis and in a mouse model of scleroderma.

METHODS

TSLP expression was analysed by immunohistochemistry in human SSc skin, primary lung fibrosis and mouse bleomycin-induced skin fibrosis, and by quantitative RT-PCR in mouse skin and cultured fibroblasts. The regulation of TSLP expression by specific toll-like receptors (TLR)-2, -3 and -4 agonists was analysed in human dermal fibroblast cultures. The role of TSLP in skin fibrosis and local cytokine expression was analysed in TSLP receptor (TSLPR)-deficient mice.

RESULTS

TSLP was overexpressed by epithelial cells, mast cells and fibroblasts in human SSc skin and lung fibrosis, and in the bleomycin model of scleroderma. In cultured human and mouse skin fibroblasts, TSLP expression was inducible by activation of TLR, particularly TLR3. In TSLPR-deficient mice, bleomycin-induced fibrosis was significantly reduced in parallel with significantly reduced local expression of IL-13.

CONCLUSIONS

These data provide the first evidence of TSLP overexpression in SSc and other non-allergic fibrotic conditions, and demonstrate a profibrotic role that is potentially meditated by specific changes in the local cytokine milieu. Thus, modulating TSLP may have antifibrotic therapeutic implications.

Enhanced T cell lymphoma in NOD.Stat5b transgenic mice is caused by hyperactivation of Stat5b in CD8+ thymocytes

Activation of signal transducers and activators of transcription (STAT) proteins may be critical to their oncogenic functions as demonstrated by the development of B-cell lymphoma/leukemia in transgenic (TG) mice overexpressing a constitutively activated form of Stat5b. However, low incidence of CD8⁺ T cell lymphoma was observed in B6 transgenic mice overexpressing a wild-type Stat5b (B6.Stat5b^Tg) despite of undetectable Stat5b phosphorylation and the rate of lymphomagenesis was markedly enhanced by immunization or the introduction of TCR transgenes [1]. Here, we report that the wild-type Stat5b transgene leads to the acceleration and high incidence (74%) of CD8⁺ T cell lymphoblastic lymphomas in the non-obese-diabetic (NOD) background. In contrast to the B6.Stat5b^Tg mice, Stat5b in transgenic NOD (NOD.Stat5b^Tg) mice is selectively and progressively phosphorylated in CD8⁺ thymocytes. Stat5 phosphorylation also leads to up-regulation of many genes putatively relevant to tumorigenesis. Treatment of NOD.Stat5b^Tg mice with cancer chemopreventive agents Apigenin and Xanthohumol efficiently blocked lymphomagenesis through reduction of Stat5 phosphorylation and genes up-regulated in the NOD.Stat5b^Tg mice. These results suggest that NOD genetic background is critical to the Stat5b-mediated lymphomagenesis through regulation of Stat5 hyperactivation. NOD.Stat5b^Tg mouse is an excellent model for studying the molecular mechanisms underlying lymphomagenesis and testing novel chemoprevention strategies.

Regulatory B cell (B10 Cell) expansion during Listeria infection governs innate and cellular immune responses in mice

Pathogens use numerous methods to subvert host immune responses, including the modulation of host IL-10 production by diverse cell types. However, the B cell sources of IL-10 and their overall influence on innate and cellular immune responses have not been well characterized during infections. Using Listeria as a model pathogen, infection drove the acute expansion of a small subset of regulatory B cells (B10 cells) that potently suppress inflammation and autoimmunity through the production of IL-10. Unexpectedly, spleen bacteria loads were 92-97% lower in B10 cell-deficient CD19(-/-) mice, in mice depleted of mature B cells, and in mice treated with CD22 mAb to preferentially deplete B10 cells before infection. By contrast, the adoptive transfer of wild-type B10 cells reduced bacterial clearance by 38-fold in CD19(-/-) mice through IL-10-dependent pathways. B10 cell depletion using CD22 mAb significantly enhanced macrophage phagocytosis of Listeria and their production of IFN-γ, TNF-α, and NO ex vivo. Accelerated bacteria clearance following B10 cell depletion significantly reduced Ag-specific CD4(+) T cell proliferation and cytokine production, but did not alter CD8(+) T cell responses. B10 cell regulatory function during innate immune responses was nonetheless dependent on cognate interactions with CD4(+) T cells because B10 cells deficient in IL-10, MHC-II, or IL-21R expression did not influence Listeria clearance. Thus, Listeria manipulates immune responses through a strategy of immune evasion that involves the preferential expansion of endogenous B10 cells that regulate the magnitude and duration of both innate and cellular immune responses.

TSLP: A Key Regulator of Asthma Pathogenesis

Asthma is a complex disorder of the airways that is characterized by T helper type 2 (Th2) inflammation. The pleiotrophic cytokine TSLP has emerged as an important player involved in orchestrating the inflammation seen in asthma and other atopic diseases. Early research elucidated the role of TSLP on CD4⁺ T cells, and recent work has revealed the impact of TSLP on multiple cell types. Furthermore, TSLP plays an important role in the sequential progression of atopic dermatitis to asthma, clarifying the key role of TSLP in the pathogenesis of asthma, a finding with therapeutic implications.

Mechanistic and structural insight into the functional dichotomy between IL-2 and IL-15

Interleukin 15 (IL-15) and IL-2 have distinct immunological functions even though both signal through the receptor subunit IL-2Rβ and the common γ-chain (γ(c)). Here we found that in the structure of the IL-15-IL-15Rα-IL-2Rβ-γ(c) quaternary complex, IL-15 binds to IL-2Rβ and γ(c) in a heterodimer nearly indistinguishable from that of the IL-2-IL-2Rα-IL-2Rβ-γ(c) complex, despite their different receptor-binding chemistries. IL-15Rα substantially increased the affinity of IL-15 for IL-2Rβ, and this allostery was required for IL-15 trans signaling. Consistent with their identical IL-2Rβ-γ(c) dimer geometries, IL-2 and IL-15 showed similar signaling properties in lymphocytes, with any differences resulting from disparate receptor affinities. Thus, IL-15 and IL-2 induced similar signals, and the cytokine specificity of IL-2Rα versus IL-15Rα determined cellular responsiveness. Our results provide new insights for the development of specific immunotherapeutics based on IL-15 or IL-2.

Regulatory B cells control T-cell autoimmunity through IL-21-dependent cognate interactions

B cells regulate immune responses by producing antigen-specific antibodies. However, specific B-cell subsets can also negatively regulate T-cell immune responses, and have been termed regulatory B cells. Human and mouse regulatory B cells (B10 cells) with the ability to express the inhibitory cytokine interleukin-10 (IL-10) have been identified. Although rare, B10 cells are potent negative regulators of antigen-specific inflammation and T-cell-dependent autoimmune diseases in mice. How B10-cell IL-10 production and regulation of antigen-specific immune responses are controlled in vivo without inducing systemic immunosuppression is unknown. Using a mouse model for multiple sclerosis, here we show that B10-cell maturation into functional IL-10-secreting effector cells that inhibit in vivo autoimmune disease requires IL-21 and CD40-dependent cognate interactions with T cells. Moreover, the ex vivo provision of CD40 and IL-21 receptor signals can drive B10-cell development and expansion by four-million-fold, and generate B10 effector cells producing IL-10 that markedly inhibit disease symptoms when transferred into mice with established autoimmune disease. The ex vivo expansion and reinfusion of autologous B10 cells may provide a novel and effective in vivo treatment for severe autoimmune diseases that are resistant to current therapies.

Critical Role of STAT5 transcription factor tetramerization for cytokine responses and normal immune function

Cytokine-activated STAT proteins dimerize and bind to high-affinity motifs, and N-terminal domain-mediated oligomerization of dimers allows tetramer formation and binding to low-affinity tandem motifs, but the functions of dimers versus tetramers are unknown. We generated Stat5a-Stat5b double knockin (DKI) N-domain mutant mice in which STAT5 proteins form dimers but not tetramers, identified cytokine-regulated genes whose expression required STAT5 tetramers, and defined dimer versus tetramer consensus motifs. Whereas Stat5-deficient mice exhibited perinatal lethality, DKI mice were viable; thus, STAT5 dimers were sufficient for survival. Nevertheless, STAT5 DKI mice had fewer CD4(+)CD25(+) T cells, NK cells, and CD8(+) T cells, with impaired cytokine-induced and homeostatic proliferation of CD8(+) T cells. Moreover, DKI CD8(+) T cell proliferation after viral infection was diminished and DKI Treg cells did not efficiently control colitis. Thus, tetramerization of STAT5 is critical for cytokine responses and normal immune function, establishing a critical role for STAT5 tetramerization in vivo.

Th17 cell-derived IL-17 is dispensable for B cell antibody production

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-γ-, IL-4- or TGF-β1-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.

Cd14 SNPs regulate the innate immune response

CD14 is a monocytic differentiation antigen that regulates innate immune responses to pathogens. Here, we show that murine Cd14 SNPs regulate the length of Cd14 mRNA and CD14 protein translation efficiency, and consequently the basal level of soluble CD14 (sCD14) and type I IFN production by murine macrophages. This has substantial downstream consequences for the innate immune response; the level of expression of at least 40 IFN-responsive murine genes was altered by this mechanism. We also observed that there was substantial variation in the length of human CD14 mRNAs and in their translation efficiency. sCD14 increased cytokine production by human dendritic cells (DCs), and sCD14-primed DCs augmented human CD4T cell proliferation. These findings may provide a mechanism for exploring the complex relationship between CD14 SNPs, serum sCD14 levels, and susceptibility to human infectious and allergic diseases.

IL-21 promotes the pathologic immune response to pneumovirus infection

IL-21 is a cytokine with pleiotropic actions, promoting terminal differentiation of B cells, increased Ig production, and the development of Th17 and T follicular helper cells. IL-21 is also implicated in the development of autoimmune disease and has antitumor activity. In this study, we investigated the role of IL-21 in host defense to pneumonia virus of mice (PVM), which initiates an infection in mice resembling that of respiratory syncytial virus disease in humans. We found that PVM-infected mice expressed IL-21 in lung CD4(+) T cells. Following infection, Il21r(-/-) mice exhibited less lung infiltration by neutrophils than did wild-type (WT) mice and correspondingly had lower levels of the chemokine CXCL1 in bronchoalveolar lavage fluid and lung parenchyma. CD8(+), CD4(+), and γδ T cell numbers were also lower in the lungs of PVM-infected Il21r(-/-) mice than in infected WT mice, with normal Th17 cytokines but diminished IL-6 production in PVM-infected Il21r(-/-) mice. Strikingly, Il21r(-/-) mice had enhanced survival following PVM infection, and moreover, treatment of WT mice with soluble IL-21R-Fc fusion protein enhanced their survival. These data reveal that IL-21 promotes the pathogenic inflammatory effect of PVM and indicate that manipulating IL-21 signaling may represent an immunomodulatory strategy for controlling PVM and potentially other respiratory virus infections.

Unusual timing of CD127 expression by mouse uterine natural killer cells

Decidualization, a progesterone-dependent process that alters endometrial stromal cells at implantation sites in humans and rodents, is accompanied by a highly regulated, NK cell-dominated leukocyte influx into decidual basalis (DB). Whether uNK cells differentiate from uterine progenitor cells is unknown, as are the mechanisms restricting leukocytes to DB. We asked if cells expressing the early NK lineage marker CD127 (IL-7Rα) occurred in mouse decidua. CD127 was absent from gd6.5 decidual lymphoid cells but became expressed by a mature uNK cell subset in gd10.5 DB. DB and transient myometrial structures (MLAp) that ring maternal blood vessels supplying placentae expressed IL-7 and TSLP, the CD127 ligands, but with differing temporal and spatial patterns. UNK cells expressed TSLPR, and study of gd10.5 implantation sites from mice deleted for IL-7, CD127, or TSLPR suggested that IL-7 and its receptor have physiological roles in limiting expansion of immature uNK cells within MLAp, while the TSLP signaling pathway is used in DB to sustain IFN-γ production from a subset of mature uNK cells. Regionalized, dynamic expression of the additional lymphoid organ stromal markers gp38/podoplanin and ER-TR7, but not CD157, were seen by immunohistochemistry in implantation sites, and DB and MLAp contained transcripts for Aire, a tolerance-promoting factor. These observations suggest that CD127(+) NK lineage progenitors are not present in the early postimplantation period of mouse uterus and that decidualized endometrial stroma has key immunoregulatory properties.

Lack of IL-21 signal attenuates graft-versus-leukemia effect in the absence of CD8 T-cells

Previously, we have shown that IL-21R(-/-) splenocytes ameliorate GVHD as compared with wild-type splenocytes. Here, we investigated whether or not IL-21R(-/-) splenocytes diminish the graft-versus-leukemia (GVL) effect. Surprisingly, IL-21R(-/-) splenocytes efficiently eliminate leukemic cells as well as wild-type splenocytes, suggesting the retention of GVL effects in the absence of IL-21 signaling. To compare the GVL effect between IL-21R(-/-) and wild-type cells, we titrated the number of splenocytes required for the elimination of leukemic cells and found that the threshold of GVL effect was obtained between 5 × 10(5) and 5 × 10(6) with both types of splenocytes. Cotransplantation with CD8-depleted splenocytes but not with purified CD8 T-cells resulted in a significant reduction in anti-leukemic effect of IL-21R(-/-) cells compared with wild-type cells, suggesting that the lack of IL-21 signaling primarily impairs CD4 T-cell rather than CD8 T-cell function and the comparable GVL effect with IL-21R(-/-) bulk splenocytes results from cooperative compensation by CD8 T-cells.

IL-21 is an antitolerogenic cytokine of the late-phase alloimmune response

OBJECTIVE

Interleukin-21 (IL-21) is a proinflammatory cytokine that has been shown to affect Treg/Teff balance. However, the mechanism by which IL-21 orchestrates alloimmune response and interplays with Tregs is still unclear.

RESEARCH DESIGN AND METHODS

The interplay between IL-21/IL-21R signaling, FoxP3 expression, and Treg survival and function was evaluated in vitro in immunologically relevant assays and in vivo in allogenic and autoimmune models of islet transplantation.

RESULTS

IL-21R expression decreases on T cells and B cells in vitro and increases in the graft in vivo, while IL-21 levels increase in vitro and in vivo during anti-CD3/anti-CD28 stimulation/allostimulation in the late phase of the alloimmune response. In vitro, IL-21/IL-21R signaling (by using rmIL-21 or genetically modified CD4(+) T cells [IL-21 pOrf plasmid-treated or hIL-21-Tg mice]) enhances the T-cell response during anti-CD3/anti-CD28 stimulation/allostimulation, prevents Treg generation, inhibits Treg function, induces Treg apoptosis, and reduces FoxP3 and FoxP3-dependent gene transcripts without affecting FoxP3 methylation status. In vivo targeting of IL-21/IL-21R expands intragraft and peripheral Tregs, promotes Treg neogenesis, and regulates the antidonor immune response, whereas IL-21/IL-21R signaling in Doxa-inducible ROSA-rtTA-IL-21-Tg mice expands Teffs and FoxP3(-) cells. Treatment with a combination of mIL-21R.Fc and CTLA4-Ig (an inhibitor of the early alloimmune response) leads to robust graft tolerance in a purely alloimmune setting and prolonged islet graft survival in NOD mice.

CONCLUSIONS

IL-21 interferes with different checkpoints of the FoxP3 Treg chain in the late phase of alloimmune response and, thus, acts as an antitolerogenic cytokine. Blockade of the IL-21/IL-21R pathway could be a precondition for tolerogenic protocols in transplantation.

Induction of thymic stromal lymphopoietin production by xylene and exacerbation of picryl chloride-induced allergic inflammation in mice

BACKGROUND

Some chemical compounds in the environment worsen allergic inflammation. In this study, we examined whether organic solvents induce the production of thymic stromal lymphopoietin (TSLP) which elicits Th2-type immune responses.

METHODS

Organic solvents were painted on the earlobes of BALB/c mice. The expression of TSLP in the ear was determined by ELISA.

RESULTS

Xylene and toluene, but not chloroform or ethyl acetate, induced the expression of mRNA for TSLP in the earlobe tissue. Among the aromatic compounds, xylene, especially m-xylene, and trimethylbenzene caused apparent TSLP production. The level of TSLP in the xylene-treated earlobes reached a maximum at 24 h, and TSLP was expressed in epithelial tissues. Production of TSLP was unaffected in mast cell-deficient W/W(v) mice but apparently diminished in TNF-α knockout mice and IL-4 receptor knockout mice. Repeated painting of xylene for 7 days induced an increase in the weight of cervical lymph nodes and expression of OX40 ligand, both of which were inhibited in TSLP receptor knockout mice. Xylene promoted the picryl chloride-induced thickening of the ear and IL-4 production, which were reversed in TSLP receptor knockout mice.

CONCLUSION

Xylene induced TSLP production, resulting in an exacerbation of allergic inflammation. Thus, xylene might be a good tool for examining the roles of TSLP in eliciting allergy in experimental animals.

IL-2 family cytokines: new insights into the complex roles of IL-2 as a broad regulator of T helper cell differentiation

Interleukin-2 (IL-2) is a pleiotropic cytokine that drives T-cell growth, augments NK cytolytic activity, induces the differentiation of regulatory T cells, and mediates activation-induced cell death. Along with IL-4, IL-7, IL-9, IL-15, and IL-21, IL-2 shares the common cytokine receptor γ chain, γ(c), which is mutated in humans with X-linked severe combined immunodeficiency. Herein, we primarily focus on the recently discovered complex roles of IL-2 in broadly modulating T cells for T helper cell differentiation. IL-2 does not specify the type of Th differentiation that occurs; instead, IL-2 modulates expression of receptors for other cytokines and transcription factors, thereby either promoting or inhibiting cytokine cascades that correlate with each Th differentiation state. In this fashion, IL-2 can prime and potentially maintain Th1 and Th2 differentiation as well as expand such populations of cells, whereas it inhibits Th17 differentiation but also can expand Th17 cells.

IL-2 family cytokines: new insights into the complex roles of IL-2 as a broad regulator of T helper cell differentiation

Interleukin-2 (IL-2) is a pleiotropic cytokine that drives T-cell growth, augments NK cytolytic activity, induces the differentiation of regulatory T cells, and mediates activation-induced cell death. Along with IL-4, IL-7, IL-9, IL-15, and IL-21, IL-2 shares the common cytokine receptor γ chain, γ(c), which is mutated in humans with X-linked severe combined immunodeficiency. Herein, we primarily focus on the recently discovered complex roles of IL-2 in broadly modulating T cells for T helper cell differentiation. IL-2 does not specify the type of Th differentiation that occurs; instead, IL-2 modulates expression of receptors for other cytokines and transcription factors, thereby either promoting or inhibiting cytokine cascades that correlate with each Th differentiation state. In this fashion, IL-2 can prime and potentially maintain Th1 and Th2 differentiation as well as expand such populations of cells, whereas it inhibits Th17 differentiation but also can expand Th17 cells.

Thymic stromal lymphopoietin is produced by dendritic cells

Thymic stromal lymphopoietin (TSLP) is a type 1 cytokine that contributes to lymphopoiesis and the development of asthma and atopic dermatitis. TSLP acts on multiple lineages, including dendritic cells (DCs), T cells, NKT cells, eosinophils, and mast cells, mediating proliferation and survival and linking innate and adaptive immune responses. TSLP is produced by a range of cells, including epithelial cells, fibroblasts, stromal cells, and keratinocytes. DCs are important primary targets of TSLP, and we unexpectedly demonstrated that DCs also produce TSLP in response to TLR stimulation and that this is augmented by IL-4. Moreover, we demonstrated that when mice were challenged with house dust mite extract, lung CD11c(+) DCs expressed TSLP mRNA at an even higher level than did epithelial cells. These data suggested that DCs not only respond to TSLP but also are a source of TSLP during pathogen and/or allergen encounter.