Concomitant type I IFN receptor‐triggering of T cells and of DC is required to promote maximal modified vaccinia virus Ankara‐induced T‐cell expansion

Virus‐induced expansion of CD8⁺ T cells may be promoted by type I IFN receptor (IFNAR)‐triggering of T cells, depending on the pathogen tested. We studied modified vaccinia virus Ankara (MVA), a promising vaccine vector candidate, which was derived from conventional vaccinia virus (VACV) by more than 570 consecutive in vitro passages. In adoptive transfer experiments, we verified that VACV expressing the gp33 epitope of lymphocytic choriomeningitis virus (VACV_gp33) induced largely IFNAR‐independent expansion of gp33‐specific T cells. On the contrary, MVA_gp33‐induced T‐cell expansion was IFNAR dependent. Interestingly, under the latter conditions, T‐cell activation was IFNAR independent, whereas T‐cell apoptosis was enhanced in the absence of IFNAR. To address whether MVA‐induced T‐cell expansion was solely affected by IFNAR‐triggering of T cells, expansion of endogenous T cells was studied in conditional mice with a T‐cell‐ or DC‐specific IFNAR deletion. Interestingly, both mouse strains showed moderately reduced T‐cell expansion, whereas mice with a combined T‐cell‐ and DC‐specific IFNAR ablation showed massively reduced T‐cell expansion similar to that of IFNAR^?/? mice. These results are compatible with the model that IFN‐inducing viruses such as MVA confer virus‐specific CD8⁺ T‐cell expansion by concomitant IFNAR‐triggering of DC and of T cells.     

Type I interferons contribute to experimental cerebral malaria development in response to sporozoite or blood‐stage Plasmodium berghei ANKA

Cerebral malaria is a severe complication of Plasmodium falciparum infection. Although T‐cell activation and type II IFN‐γ are required for Plasmodium berghei ANKA (PbA)‐induced murine experimental cerebral malaria (ECM), the role of type I IFN‐α/β in ECM development remains unclear. Here, we address the role of the IFN‐α/β pathway in ECM devel‐opment in response to hepatic or blood‐stage PbA infection, using mice deficient for types I or II IFN receptors. While IFN‐γR1^?/? mice were fully resistant, IFNAR1^?/? mice showed delayed and partial protection to ECM after PbA infection. ECM resistance in IFN‐γR1^?/? mice correlated with unaltered cerebral microcirculation and absence of ischemia, while WT and IFNAR1^?/? mice developed distinct microvascular pathologies. ECM resistance appeared to be independent of parasitemia. Instead, key mediators of ECM were attenuated in the absence of IFNAR1, including PbA‐induced brain sequestration of CXCR3⁺‐activated CD8⁺ T cells. This was associated with reduced expression of Granzyme B, IFN‐γ, IL‐12Rβ2, and T‐cell‐attracting chemokines CXCL9 and CXCL10 in IFNAR1^?/? mice, more so in the absence of IFN‐γR1. Therefore, the type I IFN‐α/β receptor pathway contributes to brain T‐cell responses and microvascular pathology, although it is not as essential as IFN‐γ for the development of cerebral malaria upon hepatic or blood‐stage PbA infection.     

IFN‐γ‐STAT1 signal regulates the differentiation of inducible Treg: Potential role for ROS‐mediated apoptosis

Regulatory CD4⁺ T cells are important for the homeostasis of immune cells, and their absence correlates with autoimmune disorders. However, how the immune system regulates Treg homeostasis remains unclear. We found that IFN‐γ‐deficient‐mice had more forkhead box P3 (FOXP3⁺) cells than WT mice in all secondary lymphoid organs except the thymus. However, T‐bet‐ or IL‐4Rα‐deficient mice did not show a similar increase. In vitro differentiation studies showed that conversion of naïve T cells into FOXP3⁺ cells (neo‐generated inducible Treg (iTreg)) by TGF‐β was significantly inhibited by IFN‐γ in a STAT‐1‐dependent manner. Moreover, an in vivo adoptive transfer study showed that inhibition of FOXP3⁺ iTreg generation by IFN‐γ was a T‐cell autocrine effect. This inhibitory effect of IFN‐γ on iTreg generation was significantly abrogated after N‐acetyl‐L ‐cysteine treatment both in vitro and in vivo, indicating that IFN‐γ regulation of iTreg generation is dependent on ROS‐mediated apoptosis. Therefore, our results suggest that autocrine IFN‐γ can negatively regulate the neo‐generation of FOXP3⁺ iTreg through ROS‐mediated apoptosis in the periphery.     

MAPK3 deficiency drives autoimmunity via DC arming

DC are professional APC that instruct T cells during the inflammatory course of EAE. We have previously shown that MAPK3 (Erk1) is important for the induction of T‐cell anergy. Our goal was to determine the influence of MAPK3 on the capacity of DC to arm T‐cell responses in autoimmunity. We report that DC from Mapk3^?/? mice have a significantly higher membrane expression of CD86 and MHC‐II and – when loaded with the myelin oligodendrocyte glycoprotein – show a superior capacity to prime naïve T cells towards an inflammatory phenotype than Mapk3^+/+ DC. Nonetheless and as previously described, Mapk3^?/? mice were only slightly but not significantly more susceptible to myelin oligodendrocyte glycoprotein‐induced EAE than WT littermate mice. However, Mapk3^+/+ mice engrafted with Mapk3^?/? BM (KO→WT) developed a severe form of EAE, in direct contrast to WT→KO mice, which were even less sick than control WT→WT mice. An infiltration of DC and accumulation of Th17 cells was also observed in the CNS of KO→WT mice. Therefore, triggering of MAPK3 in the periphery might be a therapeutic option for the treatment of neuroinflammation since absence of this kinase in the immune system leads to severe EAE.     

Autophagy is involved in regulating the immune response of dendritic cells to influenza A (H1N1) pdm09 infection

Autophagy can mediate antiviral immunity. However, it remains unknown whether autophagy regulates the immune response of dendritic cells (DCs) to influenza A (H1N1) pdm09 infection. In this study, we found that infection with the H1N1 virus induced DC autophagy in an endocytosis‐dependent manner. Compared with autophagy‐deficient Beclin‐1^+/? mice, we found that bone‐marrow‐derived DCs from wild‐type mice (WT BMDCs) presented a more mature phenotype on H1N1 infection. Wild‐type BMDCs secreted higher levels of interleukin‐6 (IL‐6), tumour necrosis factor‐ α (TNF‐α), interferon‐β (IFN‐β), IL‐12p70 and IFN‐γ than did Beclin‐1^+/? BMDCs. In contrast to Beclin‐1^+/? BMDCs, H1N1‐infected WT BMDCs exhibited increased activation of extracellular signal‐regulated kinase, Jun N‐terminal kinase, p38, and nuclear factor‐κB as well as IFN regulatory factor 7 nuclear translocation. Blockade of autophagosomal and lysosomal fusion by bafilomycin A1 decreased the co‐localization of H1N1 viruses, autophagosomes and lysosomes as well as the secretion of IL‐6, TNF‐α and IFN‐β in H1N1‐infected BMDCs. In contrast to Beclin‐1^+/? BMDCs, H1N1‐infected WT BMDCs were more efficient in inducing allogeneic CD4⁺ T‐cell proliferation and driving T helper type 1, 2 and 17 cell differentiation while inhibiting CD4⁺ Foxp3⁺ regulatory T‐cell differentiation. Moreover, WT BMDCs were more efficient at cross‐presenting the ovalbumin antigen to CD8⁺ T cells. We consistently found that Beclin‐1^+/? BMDCs were inferior in their inhibition of H1N1 virus replication and their induction of H1N1‐specific CD4⁺ and CD8⁺ T‐cell responses, which produced lower levels of IL‐6, TNF‐α and IFN‐β in vivo. Our data indicate that autophagy is important in the regulation of the DC immune response to H1N1 infection, thereby extending our understanding of host immune responses to the virus.     

DC therapy induces long‐term NK reactivity to tumors via host DC

We vaccinated mice with DC loaded with or without invariant NKT‐cell ligand α‐galactosylceramide and evaluated long‐term resistance against tumor challenge. When mice had been given either DC or DC/galactosylceramide and were challenged with tumor cells even 6–12 months later, both NK and NKT cells were quickly activated to express CD69 and produce IFN‐γ. The NK cells could resist a challenge with several different tumors in vivo. The activated NK and NKT cells could be depleted with anti‐NK1.1 treatment. In spite of this, the activated cells recovered, indicating that tumor‐responsive NK and NKT cells were being generated continuously as a result of vaccination with DC and were not true memory cells. The NK and NKT antitumor response in DC‐vaccinated mice depended on CD4⁺ T cells, but neither CD8⁺T cells nor CD4⁺CD25⁺ regulatory T cells. However, both vaccine DC and host DC were required for the development of long‐term, tumor reactive innate immunity. These results indicate that DC therapy in mice induces long‐lasting innate NK‐ and NKT‐cell activation through a pathway that requires host DC and CD4⁺ T cells and that the continued generation of active NK cells resists the establishment of metastases in vivo.     

Cytokine‐dependent regulation of dendritic cell differentiation in the splenic microenvironment

The DC‐derived chemokine CCL17, a ligand of CCR4, has been shown to promote various inflammatory diseases such as atopic dermatitis, atherosclerosis, and inflammatory bowel disease. Under steady‐state conditions, and even after systemic stimulation with LPS, CCL17 is not expressed in resident splenic DCs as opposed to CD8α^?CD11b⁺ LN DCs, which produce large amounts of CCL17 in particular after maturation. Upon systemic NKT cell activation through α‐galactosylceramide stimulation however, CCL17 can be upregulated in both CD8α^? and CD8α⁺ splenic DC subsets and enhances cross‐presentation of exogenous antigens. Based on genome‐wide expression profiling, we now show that splenic CD11b⁺ DCs are susceptible to IFN‐γ‐mediated suppression of CCL17, whereas LN CD11b⁺CCL17⁺ DCs downregulate the IFN‐γR and are much less responsive to IFN‐γ. Under inflammatory conditions, particularly in the absence of IFN‐γ signaling in IFN‐γRKO mice, CCL17 expression is strongly induced in a major proportion of splenic DCs by the action of GM‐CSF in concert with IL‐4. Our findings demonstrate that the local cytokine milieu and differential cytokine responsiveness of DC subsets regulate lymphoid organ specific immune responses at the level of chemokine expression.     

Myeloid‐derived suppressor cell activation by combined LPS and IFN‐γ treatment impairs DC development

Myeloid‐derived suppressor cells (MDSC) and DC are major controllers of immune responses against tumors or infections. However, it remains unclear how DC development and MDSC suppressor activity both generated from myeloid precursor cells are regulated. Here, we show that the combined treatment of BM‐derived MDSC with LPS plus IFN‐γ inhibited the DC development but enhanced MDSC functions, such as NO release and T‐cell suppression. This was not observed by the single treatments in vitro. In the spleens of healthy mice, we identified two Gr‐1^lowCD11b^highLy‐6C^highSSC^lowMo‐MDSC and Gr‐1^highCD11b^lowPMN‐MDSC populations with suppressive potential, whereas Gr‐1^highCD11b^high neutrophils and Gr‐1^lowCD11b^highSSC^low eosinophils were not suppressive. Injections of LPS plus IFN‐γ expanded these populations within the spleen but not LN leading to the block of the proliferation of CD8⁺ T cells. At the same time, their capacity to develop into DC was impaired. Together, our data suggest that spleens of healthy mice contain two subsets of MDSC with suppressive potential. A two‐signal‐program through combined LPS and IFN‐γ treatment expands and fully activates MDSC in vitro and in vivo.     

DC within the pregnant mouse uterus influence growth and functional properties of uterine NK cells

The vascular addressins mucosal addressin cell adhesion molecule‐1, P‐selectin and ICAM‐1 permit α₄β₇‐integrin‐expressing DC, especially those of the myeloid lineage (CD11c⁺CD11b⁺ DC), to access the pregnant mouse uterus. Injection of blocking monoclonal antibodies against mucosal addressin cell adhesion molecule‐1 in P‐selectin^?/? mice or experimental approaches with β7‐integrin^?/? or ICAM‐1^?/? mice revealed that limited access or absence of CD11c⁺CD11b⁺ DC at the maternal/fetal interface negatively affects the frequency, size and functional properties of uterine NK (uNK) cells. Adoptive transfer of DC obtained from WT mice into β7‐integrin^?/? mice abrogates these effects and emphasizes the importance of DC in uNK cell differentiation. Interestingly, those implantation sites lacking CD11c⁺CD11b⁺ DC are characterized by decreased IL‐15 and IL‐12 mRNA and/or protein levels. Chronic administration of IL‐15 in these mice gives rise to uNK cell numbers and size comparable to those of WT mice, whereas additional injection of IL‐12 positively affects the IFN‐γ expression of uNK cells. Real‐time RT‐PCR and protein arrays performed with isolated uterine DC underline the role of DC as a source of IL‐15 and IL‐12 in the pregnant mouse uterus.     

Targeting SIRP‐α protects from type 2‐driven allergic airway inflammation

The interplay between innate and adaptive immune responses is essential for the establishment of allergic diseases. CD47 and its receptor, signal regulatory protein α (SIRP‐α), govern innate cell trafficking. We previously reported that administration of CD47^+/+ but not CD47^−/− SIRP‐α⁺ BM‐derived DC (BMDC) induced airway inflammation and Th2 responses in otherwise resistant CD47‐deficient mice. We show here that early administration of a CD47‐Fc fusion molecule suppressed the accumulation of SIRP‐α⁺ DC in mediastinal LN, the development of systemic and local Th2 responses as well as airway inflammation in sensitized and challenged BALB/c mice. Mechanistic studies highlighted that SIRP‐α ligation by CD47‐Fc on BMDC did not impair Ag uptake, Ag presentation and Ag‐specific DO11.10 Tg Th2 priming and effector function in vitro, whereas in vivo administration of CD47‐Fc or CD47‐Fc‐pretreated BMDC inhibited Tg T‐cell proliferation, pinpointing that altered DC trafficking accounts for defective Th priming. We conclude that the CD47/SIRP‐α axis may be harnessed in vivo to suppress airway SIRP‐α⁺ DC homing to mediastinal LN, Th2 responses and allergic airway inflammation.     

Anti‐retroviral effects of type I IFN subtypes in vivo

Type I IFN play a very important role in immunity against viral infections. Murine type I IFN belongs to a multigene family including 14 IFN‐α subtypes but the biological functions of IFN‐α subtypes in retroviral infections are unknown. We have used the Friend retrovirus model to determine the anti‐viral effects of IFN‐α subtypes in vitro and in vivo. IFN‐α subtypes α1, α4, α6 or α9 suppressed Friend virus (FV) replication in vitro, but differed greatly in their anti‐viral efficacy in vivo. Treatment of FV‐infected mice with the IFN‐α subtypes α1, α4 or α9, but not α6 led to a significant reduction in viral loads. Decreased splenic viral load after IFN‐α1 treatment correlated with an expansion of activated FV‐specific CD8⁺ T cells and NK cells into the spleen, whereas in IFN‐α4‐ and ‐α9‐treated mice it exclusively correlated with the activation of NK cells. The results demonstrate the distinct anti‐retroviral effects of different IFN‐α subtypes, which may be relevant for new therapeutic approaches.     

Effects of type I interferons in malaria

Type I interferons (IFNs) are a family of cytokines with a wide range of biological activities including anti‐viral and immune‐regulatory functions. Here, we focus on the protozoan parasitic disease malaria, and examine the effects of type I IFN‐signalling during Plasmodium infection of humans and experimental mice. Since the 1960s, there have been many studies in this area, but a simple explanation for the role of type I IFN has not emerged. Although epidemiological data are consistent with roles for type I IFN in influencing malaria disease severity, functional proof of this remains sparse in humans. Several different rodent‐infective Plasmodium species have been employed in in vivo studies of parasite‐sensing, experimental cerebral malaria, lethal malaria, liver‐stage infection, and adaptive T‐cell and B‐cell immunity. A range of different outcomes in these studies suggests a delicately balanced, multi‐faceted and highly complex role for type I IFN‐signalling in malaria. This is perhaps unsurprising given the multiple parasite‐sensing pathways that can trigger type I IFN production, the multiple isoforms of IFN‐α/β that can be produced by both immune and non‐immune cells, the differential effects of acute versus chronic type I IFN production, the role of low level ‘tonic’ type I IFN‐signalling, and that signalling can occur via homodimeric IFNAR1 or heterodimeric IFNAR1/2 receptors. Nevertheless, the data indicate that type I IFN‐signalling controls parasite numbers during liver‐stage infection, and depending on host–parasite genetics, can be either detrimental or beneficial to the host during blood‐stage infection. Furthermore, type I IFN can promote cytotoxic T lymphocyte immune pathology and hinder CD4⁺ T helper cell‐dependent immunity during blood‐stage infection. Hence, type I IFN‐signalling plays highly context‐dependent roles in malaria, which can be beneficial or detrimental to the host.     

Interleukin (IL)-21-independent pathogen-specific CD8+ T-cell expansion, and IL-21-dependent suppression of CD4+ T-cell IL-17 production

Although interleukin‐21 (IL‐21) potently activates and controls the differentiation of immune cells after stimulation in vitro, the role for this pleiotropic cytokine during in vivo infection remains poorly defined. Herein, the requirement for IL‐21 in innate and adaptive host defence after Listeria monocytogenes infection was examined. In the innate phase, IL‐21 deficiency did not cause significant defects in infection susceptibility, or in the early activation of natural killer and T cells. In the adaptive phase, L. monocytogenes‐specific CD8⁺ T cells expand to a similar magnitude in IL‐21‐deficient mice compared with control mice. Interestingly, the IL‐21‐independent expansion of L. monocytogenes‐specific CD8⁺ T cells was maintained even in the combined absence of IL‐12 and type I interferon (IFN) receptor. Similarly, L. monocytogenes‐specific CD4⁺ T cells expanded and produced similar levels of IFN‐γ regardless of IL‐21 deficiency. Unexpectedly however, IL‐21 deficiency caused significantly increased CD4⁺ T‐cell IL‐17 production, and this effect became even more pronounced after L. monocytogenes infection in mice with combined defects in both IL‐12 and type I IFN receptor that develop a T helper type 17‐dominated CD4⁺ T‐cell response. Despite increased CD4⁺ T‐cell IL‐17 production, L. monocytogenes‐specific T cells re‐expanded and conferred protection against secondary challenge with virulent L. monocytogenes regardless of IL‐21 deficiency, or combined defects in IL‐21, IL‐12, and type I IFN receptor. Together, these results demonstrate non‐essential individual and combined roles for IL‐21, IL‐12 and type I IFNs in priming pathogen‐specific CD8⁺ T cells, and reveal IL‐21‐dependent suppression of IL‐17 production by CD4⁺ T cells during in vivo infection.     

Cross-presentation of cell-associated antigens by CD8alpha+ dendritic cells is attributable to their ability to internalize dead cells

In the mouse, cross‐presentation is an exclusive property of the CD8α⁺ subset of dendritic cells (DC) but the basis for this selectivity remains unclear. Here we report that splenic CD8α⁺ DC are much superior to other DC subsets in internalizing dying cells in vitro. In contrast, CD8α⁺, CD8α^– CD4⁺ and CD8α^– CD4^– DC subsets phagocytose bacteria or latex beads to a similar extent. Although CD8α⁺ DC are better than CD4⁺ DC at presenting ovalbumin (OVA)‐loaded splenocytes to naïve OT‐I T lymphocytes, CD4⁺ DC are better at presenting OVA‐expressing Escherichia coli to the same T cells. In both cases, presentation is abrogated by lactacystin. These results show that both splenic CD8α⁺ and CD8α^– DC can present exogenous antigens on major histocompatibility complex (MHC) class I via a proteasome‐dependent pathway and suggest that the specialized cross‐presenting function of CD8α⁺ DC is a result of their ability to endocytose dying cells rather than a unique pathway for handling endosomal contents.     

Suppressive and pro‐inflammatory roles for IL‐4 in the pathogenesis of experimental drug‐induced liver injury

The pathogenesis of immune‐mediated drug‐induced liver injury (DILI) following halogenated anesthetics, carbamazepine or alcohol has not been fully elucidated. Detecting cytochrome P450 2E1 (CYP2E1) IgG4 auto‐antibodies in anesthetic DILI patients suggests a role for IL‐4 in this hapten‐mediated process. We investigated IL‐4‐mediated mechanisms using our model of experimental DILI induced by immunizing BALB/c (WT) and IL‐4^?/? (KO) mice with S100 liver proteins covalently modified by a trifluoroacetyl chloride (TFA) hapten formed following halogenated anesthetic metabolism by CYP2E1. WT mice developed more hepatitis, TFA and S100 antibodies (p<0.01), as well as T‐cell proliferation to CYP2E1 and TFA (p<0.01) than KO mice. Additionally, WT CD4⁺ T cells adoptively transferred hepatitis to naïve Rag^?/? mice (p<0.01). Pro‐inflammatory cytokines were expectedly decreased in TFA hapten‐stimulated KO splenocyte supernatants (p<0.001); however, IL‐2 and IFN‐γ (p<0.05), as well as IL‐6 and IL‐10 (p<0.001) levels were elevated in CYP2E1‐stimulated KO splenocyte supernatants, suggesting dual IL‐4‐mediated pro‐inflammatory and regulatory responses. Anti‐IL‐10 administered to KO mice increased hepatitis, TFA and CYP2E1 antibodies in KO mice confirming a critical role for IL‐4. This is the first demonstration of dual roles for IL‐4 in the pathogenesis of immune‐mediated DILI by suppressing auto‐antigen‐induced regulatory responses while promoting hapten‐induced pro‐inflammatory responses.     

Loss of central and peripheral CD8+ T-cell tolerance to HFE in mouse models of human familial hemochromatosis

HFE, an MHC class Ib molecule that controls iron metabolism, can be directly targeted by cytotoxic TCR αβ T lymphocytes. Transgenic DBA/2 mice expressing, in a Rag 2 KO context, an αβ TCR that directly recognizes mouse HFE (mHFE) were created to further explore the interface of HFE with the immune system. TCR‐transgenic mHfe WT mice deleted mHFE‐reactive T cells in the thymus, but a fraction of reprogrammed cells were able to escape deletion. In contrast, TCR‐transgenic mice deprived of mHFE molecules (mHfe KO mice) or expressing a C282→Y mutated mHFE molecule – the most frequent mutation associated with human hereditary hemochromatosis – positively selected mHFE‐reactive CD8⁺ T lymphocytes and were not tolerant toward mHFE. By engrafting these mice with DBA/2 WT (mHFE⁺) skin, it was established, as suspected on the basis of similar engraftments performed on DBA/2 mHfe KO mice, that mHFE behaves as an autonomous skin‐associated histocompatibility antigen, even for mHFE‐C282→Y mutated mice. By contrast, infusion of DBA/2 mHFE⁺ mice with naïve mHFE‐reactive transgenic CD8⁺ T lymphocytes did not induce GVHD. Thus, tolerance toward HFE in mHfe WT mice can be acquired at either thymic or peripheral levels but is disrupted in mice reproducing human familial hemochromatosis.     

The role of antigen-presenting cells and interleukin-12 in the priming of antigen-specific CD4+ T cells by immune stimulating complexes

Immune stimulating complexes (ISCOMs) containing the saponin adjuvant Quil A are vaccine adjuvants that promote a wide range of immune responses in vivo, including delayed-type hypersensitivity (DTH) and the secretion of both T helper 1 (Th1) and Th2 cytokines. However, the antigen-presenting cell (APC) responsible for the induction of these responses has not been characterized. Here we have investigated the role of dendritic cells (DC), macrophages (Mφ) and B cells in the priming of antigen-specific CD4⁺ T cells in vitro by ISCOMs containing ovalbumin (OVA). OVA ISCOMs pulsed bone marrow (BM)-derived DC but not BM Mφ, nor naïve B cells prime resting antigen-specific CD4⁺ T cells, and this response is greatly enhanced if DC are activated with lipopolysaccharide (LPS). Of the APC found in the spleen, only DC had the capacity to prime resting antigen specific CD4⁺ T cells following exposure to OVA ISCOMs in vitro, while Mφ and B cells were ineffective. DC, but not B cells purified from the draining lymph nodes of mice immunized with OVA ISCOMs also primed resting antigen-specific CD4⁺ T cells in vitro, suggesting that DC are also critical in vivo. Using DC and T cells from interleukin (IL)-12 p40^−/− mice, we also identified a crucial role for IL-12 in the priming of optimal CD4⁺ T cell responses by OVA ISCOMs. We suggest that DC are the principal APC responsible for the priming of CD4⁺ T cells by ISCOMs in vivo and that directed targeting of these vectors to DC may enhance their efficancy as vaccine adjuvants.     

Curcumin induces maturation-arrested dendritic cells that expand regulatory T cells in vitro and in vivo

Dendritic cells (DC) and regulatory T cells (T_regs) are vital to the development of transplant tolerance. Curcumin is a novel biological agent extracted from Curcuma longa (turmeric), with anti‐inflammatory and anti‐oxidant activity mediated via nuclear factor (NF)‐κB inhibition. We investigated the immunomodulatory effects of curcumin on human monocyte‐derived and murine DC. Human monocyte‐derived DC (hu‐Mo‐DC) were generated in the presence (CurcDC) or absence (matDC) of 25 µM curcumin, and matured using lipopolysaccharide (1 µg/ml). DC phenotype and allostimulatory capacity was assessed. CD11c⁺ DC were isolated from C57BL/6 mice, pretreated with curcumin and injected into BALB/c mice, followed by evaluation of in vivo T cell populations and alloproliferative response. Curcumin induced DC differentiation towards maturation‐arrest. CurcDC demonstrated minimal CD83 expression (<2%), down‐regulation of CD80 and CD86 (50% and 30%, respectively) and reduction (10%) in both major histocompatibility complex (MHC) class II and CD40 expression compared to matDC. CurcDC also displayed decreased RelB and interleukin (IL)‐12 mRNA and protein expression. Functionally, CurcDC allostimulatory capacity was decreased by up to 60% (P < 0·001) and intracellular interferon (IFN‐γ) expression in the responding T cell population were reduced by 50% (P < 0·05). T cell hyporesponsiveness was due to generation of CD4⁺CD25^hiCD127^loforkhead box P3 (FoxP3)⁺ T_regs that exerted suppressive functions on naïve syngeneic T cells, although the effect was not antigen‐specific. In mice, in vivo infusion of allogeneic CurcDC promoted development of FoxP3⁺ T_regs and reduced subsequent alloproliferative capacity. Curcumin arrests maturation of DC and induces a tolerogenic phenotype that subsequently promotes functional FoxP3⁺ T_regsin vitro and in vivo.     

The regulatory role of interferon‐γ producing gamma delta T cells via the suppression of T helper 17 cell activity in bleomycin‐induced pulmonary fibrosis

Interstitial pneumonia (IP) is a chronic progressive interstitial lung disease associated with poor prognosis and high mortality. However, the pathogenesis of IP remains to be elucidated. The aim of this study was to clarify the role of pulmonary γδT cells in IP. In wild‐type (WT) mice exposed to bleomycin, pulmonary γδT cells were expanded and produced large amounts of interferon (IFN)‐γ and interleukin (IL)‐17A. Histological and biochemical analyses showed that bleomycin‐induced IP was more severe in T cell receptor (TCR‐δ‐deficient (TCRδ^–/–) mice than WT mice. In TCRδ^–/– mice, pulmonary IL‐17A⁺CD4⁺ Τ cells expanded at days 7 and 14 after bleomycin exposure. In TCRδ^–/– mice infused with γδT cells from WT mice, the number of pulmonary IL‐17A⁺ CD4⁺ T cells was lower than in TCRδ^–/– mice. The examination of IL‐17A^–/– TCRδ^–/– mice indicated that γδT cells suppressed pulmonary fibrosis through the suppression of IL‐17A⁺CD4⁺ T cells. The differentiation of T helper (Th)17 cells was determined in vitro, and CD4⁺ cells isolated from TCRδ^–/– mice showed normal differentiation of Th17 cells compared with WT mice. Th17 cell differentiation was suppressed in the presence of IFN‐γ producing γδT cells in vitro. Pulmonary fibrosis was attenuated by IFN‐γ‐producing γδT cells through the suppression of pulmonary IL‐17A⁺CD4⁺ T cells. These results suggested that pulmonary γδT cells seem to play a regulatory role in the development of bleomycin‐induced IP mouse model via the suppression of IL‐17A production.