IL‐33 activates eosinophils of visceral adipose tissue both directly and via innate lymphoid cells

Eosinophils are multifunctional leukocytes involved in allergic reactions as well as adipose tissue regulation. IL‐5 is required for eosinophil survival; however, the in vivo mechanisms of eosinophil regulation are not fully understood. A tg mouse model with il5 promoter‐driven EGFP expression was established for detecting the IL‐5‐producing cells in vivo. Il5‐egfp tg mice expressed high levels of EGFP in gonadal adipose tissue (GAT) cells. EGFP⁺ cells in GAT were mainly group 2 innate lymphoid cells (ILCs). IL‐33 preferentially expanded EGFP⁺ cells and eosinophils in GAT in vivo. EGFP⁺ ILCs were found to upregulate prg2 mRNA expression in GAT eosinophils. These results demonstrate that ILCs activate eosinophils in GAT. The blockage of IL‐33Rα, on the other hand, did not impair EGFP⁺ ILC numbers but did impair eosinophil numbers in vivo. GAT eosinophils expressed IL‐33Rα and IL‐33 expanded eosinophil numbers in CD90⁺ cell‐depleted mice. IL‐33 was further observed to induce the expression of retnla and epx mRNA in eosinophils. These findings demonstrate that IL‐33 directly activates eosinophils in GAT, and together with our other findings described above, our findings show that IL‐33 has dual pathways via which it activates eosinophils in vivo: a direct activation pathway and a group 2 ILC‐mediated pathway.     

An ST2‐dependent role of bone marrow‐derived group 2 innate lymphoid cells in pulmonary fibrosis

Recent evidence supports that bone marrow (BM)‐derived hematopoietic progenitor cells play an important role in lung injury and fibrosis. While these cells give rise to multiple cell types, the ST2 (Il1rl1)‐expressing group 2 innate lymphoid cells (ILC2s) derived from BM progenitors have been implicated in tissue repair and remodeling, including in lung fibrosis. To further investigate the precise role of BM‐derived ILC2s in the pathogenesis of fibrotic lung disease, their importance in the bleomycin‐induced lung fibrosis model was evaluated by analyzing the effects of selective ST2 deficiency in the BM compartment. The results showed that while ST2‐sufficient control mice exhibited activation of lung IL‐33/ST2 signaling, ILC2 recruitment, IL‐13 induction, and fibrosis, these responses were significantly diminished in ST2‐deficient‐BM chimera mice, with selective loss of ST2 expression only in the BM. This diminished response to bleomycin was similar to that seen in ST2 global knockout mice, suggesting the predominant importance of ST2 from the BM compartment. In wild‐type mice, ILC2 recruitment to the lung was accompanied by a concomitant decrease in ST2⁺ BM cells. ST2‐deficient BM cells were unresponsive to IL‐33‐induced ILC2 maturation. Finally, lineage‐negative wild‐type, but not ST2‐deficient BM cells from bleomycin‐treated mice stimulated lung fibroblast type I collagen expression, which was associated with elevated TGFβ expression in the BM cells. Taken together, these findings suggested that the BM‐derived ILC2s were recruited to fibrotic lung through the IL‐33/ST2 pathway, and contributed to fibroblast activation to promote lung fibrosis. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Functional interleukin‐33 receptors are expressed in early progenitor stages of allergy‐related granulocytes

Interleukin‐33 (IL‐33) induces T helper type 2 (Th2) cytokine production and eosinophilia independently of acquired immunity, leading to innate immunity‐mediated allergic inflammation. Allergy‐related innate myeloid cells such as eosinophils, basophils and mast cells express the IL‐33 receptor (IL‐33R), but it is still unknown how IL‐33 regulates allergic inflammation involving these cells and their progenitors. Here, we revealed that the functional IL‐33R was expressed on eosinophil progenitors (EoPs), basophil progenitors (BaPs) and mast cell progenitors (MCPs). In the presence of IL‐33, these progenitors did not expand, but produced a high amount of Th2 and pro‐inflammatory cytokines such as IL‐9, IL‐13, IL‐1β and IL‐6. The amount of cytokines produced by these progenitors was greater than that by mature cells. In vivo, IL‐33 stimulated the expansion of EoPs, but it was dependent upon the elevated serum IL‐5 that is presumably derived from type 2 innate lymphoid cells that express functional IL‐33R. These data collectively suggest that EoPs, BaPs and MCPs are not only the sources of allergy‐related granulocytes, but can also be sources of allergy‐related cytokines in IL‐33‐induced inflammation. Because such progenitors can differentiate into mature granulocytes at the site of inflammation, they are potential therapeutic targets in IL‐33‐related allergic diseases.     

Interferon‐γ constrains cytokine production of group 2 innate lymphoid cells

Group 2 innate lymphoid cells (ILC2s) produce a significant amount of interleukin‐5 (IL‐5), which supports eosinophil responses in various tissues; they also produce IL‐13, which induces mucus production and contributes to tissue repair or fibrosis. The ILC2s are activated by alarmins, such as IL‐33 released from epithelia, macrophages and natural killer T (NKT) cells in response to infection and allergen exposure, leading to epithelial injury. We examined gene expression in lung ILC2s and found that ILC2s expressed Ifngr1, the receptor for interferon‐γ (IFN‐γ). Interferon‐γ severely inhibited IL‐5 and IL‐13 production by lung and kidney ILC2s. To evaluate the effects in vivo, we used α‐galactosylceramide (α‐GalCer) to induce NKT cells to produce IL‐33 and IFN‐γ. Intraperitoneal injection of α‐GalCer in mice induced NKT cell activation resulting in IL‐5 and IL‐13 production by ILC2s. Administration of anti‐IFN‐γ together with α‐GalCer significantly enhanced the production of IL‐5 and IL‐13 by ILC2s in lung and kidney. Conversely, cytokine production from ILC2s was markedly suppressed after injection of exogenous IL‐33 in Il33^?/? mice pre‐treated with α‐GalCer. Hence, IFN‐γ induced or already present in tissues can impact downstream pleiotropic functions mediated by ILC2s, such as inflammation and tissue repair.     

CD8+ T cells producing IL‐3 and IL‐5 in non‐IgE‐mediated eosinophilic diseases

The cytokines IL‐5, IL‐3, and GM‐CSF are crucial for eosinophil development, survival, and function. To better understand their role in non‐IgE‐mediated eosinophilic diseases, we investigated plasma levels of these cytokines as well as cytokine expression in peripheral blood T cells. While we did not find any evidence for an involvement of T‐cell‐derived GM‐CSF, some of these patients did show an increased proportion of IL‐5‐ or IL‐3‐producing CD4⁺ T cells. However, in a significant proportion of patients, IL‐5‐producing CD8⁺ T cells, so‐called Tc2 cells, which in healthy donors can only be detected at very low levels, were prominent. Furthermore, increased IL‐3 production by CD8⁺ T cells was also observed, strongly supporting the notion that CD8⁺ T cells, not just CD4⁺ T cells, must also be considered as a potential source of the cytokines promoting eosinophilia.     

Interleukin‐13 directly promotes oesophagus production of CCL11 and CCL24 and the migration of eosinophils

Background Eosinophilic oesophagitis (EE) is a clinico‐pathologically defined oesophageal disorder that is characterized by eosinophil migration into oesophageal tissues. There is growing support for EE being an allergic disease and for a contribution of T‐helper type 2 (Th2)‐associated cytokines in disease pathogenesis. The respiratory system has been shown to be critical in driving the development of EE in animal models. However, the mechanisms underlying the recruitment of eosinophils into the oesophagus remain unclear. Objective We sought to investigate the influence of Th2‐associated cytokines on the production of eosinophil‐specific chemokines from the oesophagus directly. Methods In order to eliminate the potential involvement of the lung, we utilized isolated oesophageal rings. These were treated in vitro with IL‐4 or IL‐13 and the expression and production of CCL11 and CCL24 were determined. Results Our data demonstrate that IL‐13 is a potent and direct inducer of both CCL11 and CCL24 production from the oesophagus, as is IL‐4 also. The expression of CCL11 precedes CCL24 by several hours but then diminishes over time, as well as at high concentrations of IL‐13. We demonstrate that there is an up‐regulation of the inhibitory IL‐13 receptor, IL‐13Rα2 but that IL‐13Rα1 remains unaltered. Oesophagus rings isolated from STAT6^?/? mice were unable to produce CCL11 or CCL24 upon IL‐13 treatment. Lastly, we demonstrate that oesophageal production of CCL11 and CCL24 upon IL‐13 stimulation is sufficient to promote eosinophil migration. Conclusions IL‐13 is capable of directly stimulating oesophageal tissue to produce eosinophil‐attracting chemokines and drive eosinophil migration. Cite this as: C. V. Neilsen and P. J. Bryce, Clinical & Experimental Allergy, 2010 (40) 427–434.     

T cells are necessary for ILC2 activation in house dust mite‐induced allergic airway inflammation in mice

Allergic asthma is a chronic inflammation of the airways mediated by an adaptive type 2 immune response. Upon allergen exposure, group 2 innate lymphoid cells (ILC2s) can be rapidly activated and represent an early innate source of IL‐5 and IL‐13. Here, we used a house dust mite (HDM)‐driven asthma mouse model to study the induction of ILC2s in allergic airway inflammation. In BALF, lungs, and lymph nodes, ILC2 activation is critically dependent on prior sensitization with HDM. Importantly, T cells are required for ILC2 induction, whereby T‐cell activation precedes ILC2 induction. During HDM‐driven allergic airway inflammation the accumulation of ILC2s in BALF is IL‐33 independent, although infiltrating ILC2s produce less cytokines in Il33^?/? mice. Transfer of in vitro polarized OVA‐specific OT‐II Th2 cells alone or in combination with Th17 cells followed by OVA and HDM challenge is not sufficient to induce ILC2, despite significant eosinophilic inflammation and T‐cell activation. In this asthma model, ILC2s are therefore not an early source of Th2 cytokines, but rather contribute to type 2 inflammation in which Th2 cells play a key role. Taken together, ILC2 induction in HDM‐mediated allergic airway inflammation in mice critically depends on activation of T cells.     

Association of serum interleukin‐33 level and the interleukin‐33 genetic variant with Japanese cedar pollinosis

Background IL‐33, an IL‐1‐like cytokine, is a ligand for IL1RL1, which is an important effector molecule of type 2 T helper responses. Although IL‐33/IL1RL1 interaction has been suggested to be important in induction of allergic airway inflammation, serum levels of IL‐33 and the genetic influences of the polymorphisms of IL‐33 in human allergic diseases are unclear. Objective The aim of this study was to examine whether the serum IL‐33 level and polymorphisms in IL‐33 are associated with Japanese cedar (JC) pollinosis, the most common form of allergic rhinitis, and a major public health problem, in Japan. Methods We performed linkage disequilibrium (LD) mapping of the gene using the HapMap database, and two selected tag single nucleotide polymorphisms were genotyped. We conducted an association study of IL‐33 (JC pollinosis, n=170; normal controls, n=100) and measured the IL‐33 levels in sera of the 270 subjects by ELISA. Results Serum levels of IL‐33 were significantly higher in patients with JC pollinosis (P=0.0018) than in controls. In genetic association analysis, we found a positive association between the polymorphism and JC pollinosis (P=0.048). Conclusion Our results support a role for IL‐33 in the pathogenesis of JC pollinosis.     

Pathogenic T helper type 17 cells contribute to type 1 diabetes independently of interleukin‐22

We have shown that pathogenic T helper type 17 (Th17) cells differentiated from naive CD4⁺ T cells of BDC2·5 T cell receptor transgenic non‐obese diabetic (NOD) mice by interleukin (IL)‐23 plus IL‐6 produce IL‐17, IL‐22 and induce type 1 diabetes (T1D). Neutralizing interferon (IFN)‐γ during the polarization process leads to a significant increase in IL‐22 production by these Th17 cells. We also isolated IL‐22‐producing Th17 cells from the pancreas of wild‐type diabetic NOD mice. IL‐27 also blocked IL‐22 production from diabetogenic Th17 cells. To determine the functional role of IL‐22 produced by pathogenic Th17 cells in T1D we neutralized IL‐22 in vivo by using anti‐IL‐22 monoclonal antibody. We found that blocking IL‐22 did not alter significantly adoptive transfer of disease by pathogenic Th17 cells. Therefore, IL‐22 is not required for T1D pathogenesis. The IL‐22Rα receptor for IL‐22 however, increased in the pancreas of NOD mice during disease progression and based upon our and other studies we suggest that IL‐22 may have a regenerative and protective role in the pancreatic islets.     

Activation of invariant natural killer T cells in regional lymph nodes as new antigen‐specific immunotherapy via induction of interleukin‐21 and interferon‐γ

Invariant natural killer T (iNKT) cells play important immunoregulatory functions in allergen‐induced airway hyperresponsiveness and inflammation. To clarify the role of iNKT cells in allergic rhinitis (AR), we generated bone marrow‐derived dendritic cells (BMDCs), which were pulsed by ovalbumin (OVA) and α‐galactosylceramide (OVA/α‐GalCer‐BMDCs) and administered into the oral submucosa of OVA‐sensitized mice before nasal challenge. Nasal symptoms, level of OVA‐specific immunoglobulin (IgE), and T helper type 2 (Th2) cytokine production in cervical lymph nodes (CLNs) were significantly ameliorated in wild‐type (WT) mice treated with OVA/α‐GalCer‐BMDCs, but not in WT mice treated with OVA‐BMDCs. These anti‐allergic effects were not observed in Jα18^–/– recipients that lack iNKT cells, even after similar treatment with OVA/α‐GalCer‐BMDCs in an adoptive transfer study with CD4⁺ T cells and B cells from OVA‐sensitized WT mice. In WT recipients of OVA/α‐GalCer‐BMDCs, the number of interleukin (IL)‐21‐producing iNKT cells increased significantly and the Th1/Th2 balance shifted towards the Th1 dominant state. Treatment with anti‐IL‐21 and anti‐interferon (IFN)‐γ antibodies abrogated these anti‐allergic effects in mice treated with α‐GalCer/OVA‐BMDCs. These results suggest that activation of iNKT cells in regional lymph nodes induces anti‐allergic effects through production of IL‐21 or IFN‐γ, and that these effects are enhanced by simultaneous stimulation with antigen. Thus, iNKT cells might be a useful target in development of new treatment strategies for AR.     

Secreted IL‐1α promotes T‐cell activation and expansion of CD11b+Gr1+ cells in carbon tetrachloride‐induced liver injury in mice

Interleukin‐1α is mainly expressed on the cell membrane, but can also be secreted during inflammation. The roles of secreted and membrane IL‐1α in acute liver inflammation are still not known. Here, we examined the functions of secreted and membrane IL‐1α in a mouse model of carbon tetrachloride‐induced acute liver injury. We show that secreted IL‐1α aggravates liver damage and membrane IL‐1α slightly protects mice from liver injury. Further studies showed that secreted IL‐1α promotes T‐cell activation. It also increased the expansion of CD11b⁺Gr1⁺ myeloid cells, which may serve as a negative regulator of acute liver inflammation. Moreover, secreted IL‐1α induced IL‐6 production from hepatocytes. IL‐6 neutralization reduced the proliferation of CD11b⁺Gr1⁺ myeloid cells in vivo. CCL2 and CXCL5 expression was increased by secreted IL‐1α in vitro and in vivo. Antagonists of the chemokine receptors for CCL2 and CXCL5 significantly reduced the migration of CD11b⁺Gr1⁺ myeloid cells. These results demonstrate that secreted and membrane IL‐1α play different roles in acute liver injury. Secreted IL‐1α could promote T‐cell activation and the recruitment and expansion of CD11b⁺Gr1⁺ myeloid cells through induction of CCL2, CXCL5, and IL‐6. The controlled release of IL‐1α could be a critical regulator during acute liver inflammation.     

Human umbilical cord derived mesenchymal stem cells promote interleukin‐17 production from human peripheral blood mononuclear cells of healthy donors and systemic lupus erythematosus patients

Inflammation instigated by interleukin (IL)‐17‐producing cells is central to the development and pathogenesis of several human autoimmune diseases and animal models of autoimmunity. The expansion of IL‐17‐producing cells from healthy donors is reportedly promoted by mesenchymal stem cells derived from fetal bone marrow. In the present study, human umbilical cord‐derived mesenchymal stem cells (hUC‐MSCs) were examined for their effects on lymphocytes from healthy donors and from patients with systemic lupus erythematosus (SLE). Significantly higher levels of IL‐17 were produced when CD4⁺ T cells from healthy donors were co‐cultured with hUC‐MSCs than those that were cultured alone. Blocking experiments identified that this effect might be mediated partially through prostaglandin E₂ (PGE₂) and IL‐1β, without IL‐23 involvement. We then co‐cultured hUC‐MSCs with human CD4⁺ T cells from systemic lupus erythematosus patients. Ex‐vivo inductions of IL‐17 by hUC‐MSCs in stimulated lymphocytes were significantly higher in SLE patients than in healthy donors. This effect was not observed for IL‐23. Taken together, our results represent that hUC‐MSCs can promote the IL‐17 production from CD4⁺ T cells in both healthy donor and SLE patients. PGE₂ and IL‐1β might also be partially involved in the promotive effect of hUC‐MSCs.     

IL‐12‐polarized Th1 cells produce GM‐CSF and induce EAE independent of IL‐23

CD4⁺ T‐helper (Th) cells reactive against myelin antigens mediate the mouse model experimental autoimmune encephalomyelitis (EAE) and have been implicated in the pathogenesis of multiple sclerosis (MS). It is currently debated whether encephalitogenic Th cells are heterogeneous or arise from a single lineage. In the current study, we challenge the dogma that stimulation with the monokine IL‐23 is universally required for the acquisition of pathogenic properties by myelin‐reactive T cells. We show that IL‐12‐modulated Th1 cells readily produce IFN‐γ and GM‐CSF in the CNS of mice and induce a severe form of EAE via an IL‐23‐independent pathway. Th1‐mediated EAE is characterized by monocyte‐rich CNS infiltrates, elicits a strong proinflammatory cytokine response in the CNS, and is partially CCR2 dependent. Conversely, IL‐23‐modulated, stable Th17 cells induce EAE with a relatively mild course via an IL‐12‐independent pathway. These data provide definitive evidence that autoimmune disease can be driven by distinct CD4⁺ T‐helper‐cell subsets and polarizing factors.     

An intranasal administration of Lactococcus lactis strains expressing recombinant interleukin‐10 modulates acute allergic airway inflammation in a murine model

Background Around 300 million people world‐wide suffer from asthma, and the prevalence of allergic diseases has increased. Much effort has been used in the study of mechanisms involved in the immune response observed in asthma to intervene for the treatment of this condition. During inflammation in asthma, Th2 cytokines and eosinophils are essential components of the host immune system. Furthermore, for therapeutic interventions against this disease, IL‐10 is an important cytokine because it has a central role in the regulation of inflammatory cascades. Objective To evaluate the immunomodulatory effect of Lactococcus lactis strains expressing recombinant IL‐10 in a mouse model of ovalbumin (OVA)‐induced acute airway inflammation. Methods L. lactis expressing recombinant IL‐10 in a cytoplasmic (LL‐CYT) or secreted form (LL‐SEC) and wild‐type (LL‐WT) were used. IL‐10 production by the recombinant strains was evaluated by ELISA. After an intranasal administration of L. lactis producing recombinant IL‐10 and the induction of acute allergic airway inflammation in mice, blood samples were collected to detect IgE anti‐OVA, and bronchoalveolar lavage (BAL) was harvested for eosinophil count. Additionally, the lungs were collected for the detection of the eosinophil peroxidase (EPO) activity, measurement of cytokines and chemokines and evaluation of pathology. Results Mice that received LL‐CYT and LL‐SEC strains showed a significant decrease in eosinophils numbers, EPO activity, anti‐OVA IgE and IgG1 levels, IL‐4 and CCL3 production and pulmonary inflammation and mucus hypersecretion, compared with the asthmatic group. Only the LL‐CYT/OVA group showed reduced levels of IL‐5, CCL2, CCL5 and CCL11. Conclusion Treatment with L. lactis producing recombinant IL‐10 used in this study (LL‐CYT and LL‐SEC) modulated experimental airway inflammation in the mouse model independently of Treg cells. Additionally, the LL‐CYT strain was more efficient in the suppression of lung inflammation. Cite this as: F. A. V. Marinho, L. G. G. Pacífico, A. Miyoshi, V. Azevedo, Y. Le Loir, V. D. Guimarães, P. Langella, G. D. Cassali, C. T. Fonseca and S. C. Oliveira, Clinical & Experimental Allergy, 2010 (40) 1541–1551.     

IL‐33 citrine reporter mice reveal the temporal and spatial expression of IL‐33 during allergic lung inflammation

Interleukin‐33 (IL‐33) is an IL‐1 family cytokine that signals via its receptor T1/ST2, and is a key regulator of inflammation, notably the type‐2 response implicated in allergic asthma. Critical to our understanding of the role of IL‐33 is the identification of the cellular sources of IL‐33. Although progress has been made in this area, the development of a robust live cell reporter of expression would allow the localisation of IL‐33 during ongoing immune responses. We have generated a fluorescent reporter mouse line, Il33^Cit/+, to define the expression profile of IL‐33 in vivo and demonstrate its temporal and spatial expression during experimental allergic asthma responses. We found that type‐2 pneumocytes constitute the major source of IL‐33 upon allergic lung inflammation following exposure to OVA, fungal extract or ragweed pollen. Using Il33^Cit/Cit mice (IL‐33‐deficient), we establish a role for IL‐33 early in the initiation of type‐2 responses and the induction of nuocytes (ILC2). We also demonstrate a potential mechanism of action by which IL‐33 rapidly initiates type‐2 immune responses. Il33^Cit/+ mice have enabled new insights into the initiation of type‐2 responses and will provide an important tool for further dissection of this important inflammatory pathway in vivo.     

Endogenous interleukin‐6 amplifies interleukin‐17 production and corticoid‐resistance in peripheral T cells from patients with multiple sclerosis

Interleukin‐6 (IL‐6) has been implicated in the induction of pathogenic IL‐17‐producing T cells in autoimmune diseases, and studies evaluating the role of this cytokine in T‐cell function in patients with multiple sclerosis (MS) are lacking. Our objective was to evaluate the role of IL‐6 receptor (IL‐6R) signalling on in vitro functional status of T cells from patients with relapsing–remitting MS during clinical remission. Our results demonstrated that, even during the remission phase, activated T cells from patients produce higher levels of IL‐17, and this cytokine was positively correlated with disease severity, as determined by Expanded Disability Status Scale score. In the MS group, the blockade of IL‐6R signalling by anti‐IL‐6R monoclonal antibody reduced IL‐17 production and elevated IL‐10 release by activated CD4⁺ T cells, but it did not alter the production of these cytokines by activated CD8⁺ T cells. Blockade of IL‐6R signalling also reduced the ability of monocytes to up‐regulate T helper type 17 phenotype in patients with MS. Finally, both cell proliferation and IL‐17 release by CD4⁺ and, mainly, CD8⁺ T cells from patients with MS were less sensitive to hydrocortisone inhibition than control group. Interestingly, IL‐6R signalling blockade restored the ability of hydrocortisone to inhibit both T‐cell proliferation and IL‐17 production. Collectively, these results suggest that IL‐6 might be involved in MS pathogenesis by enhancing IL‐17 production and reducing corticoid inhibitory effects on activated T cells.     

DX5+CD4+ T cells modulate CD4+ T‐cell response via inhibition of IL‐12 production by DCs

DX5⁺CD4⁺ T cells have been shown to dampen collagen‐induced arthritis and delayed‐type hypersensitivity reactions in mice. These cells are also potent modulators of T‐helper cell responses through direct effects on CD4⁺ T cells in an IL‐4 dependent manner. To further characterize this T‐cell population, we studied their effect on DCs and the potential consequences on T‐cell activation. Here, we show that mouse DX5⁺CD4⁺ T cells modulate DCs by robustly inhibiting IL‐12 production. This modulation is IL‐10 dependent and does not require cell contact. Furthermore, DX5⁺CD4⁺ T cells modulate the surface phenotype of LPS‐matured DCs. DCs modulated by DX5⁺CD4⁺ T‐cell supernatant express high levels of the co‐inhibitor molecules PDL‐1 and PDL‐2. OVA‐specific CD4⁺ T cells primed with DCs exposed to DX5⁺CD4⁺ T‐cell supernatant produce less IFN‐γ than CD4⁺ T cells primed by DCs exposed to either medium or DX5^?CD4⁺ T‐cell supernatant. The addition of IL‐12 to the co‐culture with DX5⁺ DCs restores IFN‐γ production. When IL‐10 present in the DX5⁺CD4⁺ T‐cell supernatant is blocked, DCs re‐establish their ability to produce IL‐12 and to efficiently prime CD4⁺ T cells. These data show that DX5⁺CD4⁺ T cells can indirectly affect the outcome of the T‐cell response by inducing DCs that have poor Th1 stimulatory function.     

T cell‐derived IFN‐γ downregulates protective group 2 innate lymphoid cells in murine lupus erythematosus

Innate lymphoid cells (ILCs) are important regulators of the immune response and play a crucial role in the restoration of tissue homeostasis after injury. GATA‐3⁺ IL‐13‐ and IL‐5‐producing group 2 innate lymphoid cells (ILC2s) have been shown to promote tissue repair in barrier organs, but despite extensive research on ILCs in the recent years, their potential role in autoimmune diseases is still incompletely understood. In the present study, we investigate the role of ILC2s in the MRL/MpJ‐Fas^lpr (MRL‐lpr) mouse model for severe organ manifestation of systemic lupus erythematosus (SLE). We show that in these MRL‐lpr mice, progression of lupus nephritis is accompanied with a reduction of ILC2 abundance in the inflamed renal tissue. Proliferation/survival and cytokine production of kidney‐residing ILC2s was suppressed by IFN‐γ and, to a lesser extent, by IL‐27 which were produced by activated T cells and myeloid cells in the nephritic kidney, respectively. Most importantly, restoration of ILC2 numbers by IL‐33‐mediated expansion ameliorated lupus nephritis and prevented mortality in MRL‐lpr mice. In summary, we show here that development of SLE‐like kidney inflammation leads to a downregulation of the renal ILC2 response and identify an ILC2‐expanding therapy as a promising treatment approach for autoimmune diseases.     

Preferential infiltration of interleukin‐4‐producing CXCR4+ T cells in the lesional muscle but not skin of patients with dermatomyositis

Dermatomyositis (DM) and polymyositis (PM) are collectively termed autoimmune myopathy. To investigate the difference between muscle‐ and skin‐infiltrating T cells and to address their role for myopathy, we characterized T cells that were directly expanded from the tissues. Enrolled into this study were 25 patients with DM and three patients with PM. Muscle and skin biopsied specimens were immersed in cRPMI medium supplemented with interleukin (IL)‐2 and anti‐CD3/CD28 antibody‐conjugated microbeads. The expanded cells were subjected to flow cytometry to examine their phenotypes. We analysed the cytokine concentration in the culture supernatants from the expanded T cells and the frequencies of cytokine‐bearing cells by intracellular staining. There was non‐biased in‐vitro expansion of tissue‐infiltrating CD4⁺ and CD8⁺ T cells from the muscle and skin specimens. The majority of expanded T cells were chemokine receptor (CCR) type 7^–CD45RO⁺ effecter memory cells with various T cell receptor (TCR) Vβs. The skin‐derived but not muscle‐derived T cells expressed cutaneous lymphocyte antigen (CLA) and CCR10 and secreted large amounts of IL‐17A, suggesting that T helper type 17 (Th17) cells may have a crucial role in the development of skin lesions. Notably, the frequency of IL‐4‐producing chemokine (C‐X‐C motif) receptor (CXCR)4⁺ Th2 cells was significantly higher in the muscle‐derived cells and correlated inversely with the serum creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) levels. stromal‐derived factor (SDF)‐1/CXCL12, a ligand for CXCR4, was expressed at a high level in the vascular endothelial cells between muscular fasciculi. Our study suggests that T cell populations in the muscle and skin are different, and the Th2 cell infiltrate in the muscle is associated with the low severity of myositis in DM.     

IL‐23‐driven encephalo‐tropism and Th17 polarization during CNS‐inflammation in vivo

IL‐23 but not IL‐12 is essential for the development of autoimmune tissue inflammation in mice. Conversely, IL‐12 and IL‐23 impact on the polarization of Th1 and Th17 cells, respectively. While both polarized T helper populations can mediate autoimmune inflammation, their redundancy in the pathogenesis of EAE indicates that IL‐23 exerts its crucial influence on the disease independent of its T helper polarizing capacity. To study the impact of IL‐23 and IL‐12 on the behavior of encephalitogenic T cells in vivo, we generated BM‐chimeric mice in which we can trace individual populations of IL‐23 or IL‐12 responsive T helper cells during EAE. We observed that T cells, which lack IL‐12Rβ1 (no IL‐12 and IL‐23 signaling), fail to invade the CNS and do not acquire a Th17 phenotype. In contrast, loss of IL‐12 signaling prevents Th1 polarization but does not prevent T‐cell entry into the CNS. The loss of IL‐12R engagement does not appear to alter T‐cell expansion but leads to their accumulation in secondary lymphoid organs. We found that IL‐23 licenses T cells to invade the target tissue and to exert their effector function, whereas IL‐12 is critical for Th1 differentiation, but does not influence the pathogenic capacity of auto‐reactive T helper cells in vivo.