Alternatively activated macrophages express the IL-27 receptor alpha chain WSX-1

Recycled melanoma-secreted melanosomes regulate tumor-associated macrophage diversification

Extracellular vesicles (EVs) are important mediators of communication between cells. Here, we reveal a new mode of intercellular communication by melanosomes, large EVs secreted by melanocytes for melanin transport. Unlike small EVs, which are disintegrated within the receiver cell, melanosomes stay intact within them, gain a unique protein signature, and can then be further transferred to another cell as "second-hand" EVs. We show that melanoma-secreted melanosomes passaged through epidermal keratinocytes or dermal fibroblasts can be further engulfed by resident macrophages. This process leads to macrophage polarization into pro-tumor or pro-immune cell infiltration phenotypes. Melanosomes that are transferred through fibroblasts can carry AKT1, which induces VEGF secretion from macrophages in an mTOR-dependent manner, promoting angiogenesis and metastasis in vivo. In melanoma patients, macrophages that are co-localized with AKT1 are correlated with disease aggressiveness, and immunotherapy non-responders are enriched in macrophages containing melanosome markers. Our findings suggest that interactions mediated by second-hand extracellular vesicles contribute to the formation of the metastatic niche, and that blocking the melanosome cues of macrophage diversification could be helpful in halting melanoma progression.

Single-cell, single-nucleus, and spatial transcriptomics characterization of the immunological landscape in the healthy and PSC human liver

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is an immune-mediated cholestatic liver disease for which there is an unmet need to understand the cellular composition of the affected liver and how it underlies disease pathogenesis. We aimed to generate a comprehensive atlas of the PSC liver using multi-omic modalities and protein-based functional validation.

METHODS

We employed single-cell and single-nucleus RNA sequencing (47,156 cells and 23,000 nuclei) and spatial transcriptomics (one sample by 10x Visium and five samples with Nanostring GeoMx DSP) to profile the cellular ecosystem in 10 PSC livers. Transcriptomic profiles were compared to 24 neurologically deceased donor livers (107,542 cells) and spatial transcriptomics controls, as well as 18,240 cells and 20,202 nuclei from three PBC livers. Flow cytometry was performed to validate PSC-specific differences in immune cell phenotype and function.

RESULTS

PSC explants with parenchymal cirrhosis and prominent periductal fibrosis contained a population of cholangiocyte-like hepatocytes that were surrounded by diverse immune cell populations. PSC-associated biliary, mesenchymal, and endothelial populations expressed chemokine and cytokine transcripts involved in immune cell recruitment. Additionally, expanded CD4+ T cells and recruited myeloid populations in the PSC liver expressed the corresponding receptors to these chemokines and cytokines, suggesting potential recruitment. Tissue-resident macrophages, by contrast, were reduced in number and exhibited a dysfunctional and downregulated inflammatory response to lipopolysaccharide and interferon-γ stimulation.

CONCLUSIONS

We present a comprehensive atlas of the PSC liver and demonstrate an exhaustion-like phenotype of myeloid cells and markers of chronic cytokine expression in late-stage PSC lesions. This atlas expands our understanding of the cellular complexity of PSC and has potential to guide the development of novel treatments.

IMPACT AND IMPLICATIONS

Primary sclerosing cholangitis (PSC) is a rare liver disease characterized by chronic inflammation and irreparable damage to the bile ducts, which eventually results in liver failure. Due to a limited understanding of the underlying pathogenesis of disease, treatment options are limited. To address this, we sequenced healthy and diseased livers to compare the activity, interactions, and localization of immune and non-immune cells. This revealed that hepatocytes lining PSC scar regions co-express cholangiocyte markers, whereas immune cells infiltrate the scar lesions. Of these cells, macrophages, which typically contribute to tissue repair, were enriched in immunoregulatory genes and demonstrated a lack of responsiveness to stimulation. These cells may be involved in maintaining hepatic inflammation and could be a target for novel therapies.

Polarization of M2 Tumor-Associated Macrophages (TAMs) in Cancer Immunotherapy

We have witnessed in the last decade new milestones in the treatment of various resistant cancers with new immunotherapeutic modalities. These advances have resulted in significant objective durable clinical responses in a subset of cancer patients. These findings strongly suggested that immunotherapy should be considered for the treatment of all subsets of cancer patients. Accordingly, the mechanisms underlying resistance to immunotherapy must be explored and develop new means to target these resistant factors. One of the pivotal resistance mechanisms in the tumor microenvironment (TME) is the high infiltration of tumor-associated macrophages (TAMs) that are highly immunosuppressive and responsible, in large part, of cancer immune evasion. Thus, various approaches have been investigated to target the TAMs to restore the anti-tumor immune response. One approach is to polarize the M2 TAMS to the M1 phenotype that participates in the activation of the anti-tumor response. In this review, we discuss the various and differential properties of the M1 and M2 phenotypes, the molecular signaling pathways that participate in the polarization, and various approaches used to target the polarization of the M2 TAMs into the M1 anti-tumor phenotype. These approaches include inhibitors of histone deacetylases, PI3K inhibitors, STAT3 inhibitors, TLR agonists, and metabolic reprogramming. Clearly, due to the distinct features of various cancers and their heterogeneities, a single approach outlined above might only be effective against some cancers and not others. In addition, targeting by itself may not be efficacious unless used in combination with other therapeutic modalities.

Regulatory macrophages in solid organ xenotransplantation

Due to a critical organ shortage, pig organs are being explored for use in transplantation. Differences between species, particularly in cell surface glycans, can trigger elevated immune responses in xenotransplantation. To mitigate the risk of hyperacute rejection, genetically modified pigs have been developed that lack certain glycans and express human complement inhibitors. Nevertheless, organs from these pigs may still provoke stronger inflammatory and innate immune reactions than allotransplants. Dysregulation of coagulation and persistent inflammation remain obstacles in the transplantation of pig organs into primates. Regulatory macrophages (Mregs), known for their anti-inflammatory properties, could offer a potential solution. Mregs secrete interleukin 10 and transforming growth factor beta, thereby suppressing immune responses and promoting the development of regulatory T cells. These Mregs are typically induced via the stimulation of monocytes or macrophages with macrophage colony-stimulating factor and interferon gamma, and they conspicuously express the stable marker dehydrogenase/reductase 9. Consequently, understanding the precise mechanisms governing Mreg generation, stability, and immunomodulation could pave the way for the therapeutic use of Mregs generated in vitro. This approach has the potential to reduce the required dosages and durations of anti-inflammatory and immunosuppressive medications in preclinical and clinical settings.

IL-27 Enhances γδ T Cell–Mediated Innate Resistance to Primary Hookworm Infection in the Lungs

IL-27 is a heterodimeric IL-12 family cytokine formed by noncovalent association of the promiscuous EBI3 subunit and selective p28 subunit. IL-27 is produced by mononuclear phagocytes and unfolds pleiotropic immune-modulatory functions through ligation to IL-27 receptor α (IL-27RA). Although IL-27 is known to contribute to immunity and to limit inflammation after various infections, its relevance for host defense against multicellular parasites is still poorly defined. Here, we investigated the role of IL-27 during infection with the soil-transmitted hookworm, Nippostrongylus brasiliensis, in its early host intrapulmonary life cycle. IL-27(p28) was detectable in bronchoalveolar lavage fluid of C57BL/6J wild-type mice on day 1 after s.c. inoculation. IL-27RA expression was most abundant on lung-invading γδ T cells. Il27ra^-/- mice showed increased lung parasite burden together with aggravated pulmonary hemorrhage and higher alveolar total protein leakage as a surrogate for epithelial-vascular barrier disruption. Conversely, injections of recombinant mouse (rm)IL-27 into wild-type mice reduced lung injury and parasite burden. In multiplex screens, higher airway accumulations of IL-6, TNF-α, and MCP-3 (CCL7) were observed in Il27ra^-/- mice, whereas rmIL-27 treatment showed a reciprocal effect. Importantly, γδ T cell numbers in airways were enhanced by endogenous or administered IL-27. Further analysis revealed a direct antihelminthic function of IL-27 on γδ T cells as adoptive intratracheal transfer of rmIL-27-treated γδ T cells during primary N. brasiliensis lung infection conferred protection in mice. In summary, this report demonstrates protective functions of IL-27 to control the early lung larval stage of hookworm infection.

Interleukin-27 in Tuberculosis: A Sheep in Wolf’s Clothing?

In tuberculosis (TB), protective inflammatory immune responses and the pathological sequelae of chronic inflammation significantly depend on a timely balance of cytokine expression. In contrast to other anti-inflammatory cytokines, interleukin (IL)-27 has fundamental effects in experimental Mycobacterium tuberculosis (Mtb) infection: the absence of IL-27-mediated signalling promotes a better control of mycobacterial growth on the one hand side but also leads to a chronic hyperinflammation and immunopathology later during infection. Hence, in the context of novel host-directed therapeutic approaches and vaccination strategies for the management of TB, the timely restricted blockade of IL-27 signalling may represent an advanced treatment option. In contrast, administration of IL-27 itself may allow to treat the immunopathological consequences of chronic TB. In both cases, a better knowledge of the cell type-specific and kinetic effects of IL-27 after Mtb infection is essential. This review summarizes IL-27-mediated mechanisms affecting protection and immunopathology in TB and discusses possible therapeutic applications.

Crosstalk between macrophages and natural killer cells in the tumor microenvironment

The tumor microenvironment (TME) is jointly constructed by a variety of cell types, including tumor cells, immune cells, fibroblasts, and epithelial cells, among others. The cells within the TME interact with each other and with tumor cells to influence tumor development and progression. As the most abundant immune cells in the TME, macrophages regulate the immune network by not only secreting a large amount of versatile cytokines but also expressing a series of ligands or receptors on the surface to interact with other cells directly. Due to their strong plasticity, they exert both immunostimulatory and immunosuppressive effects in the complex TME. The major effector cells of the immune system that directly target cancer cells include but are not limited to natural killer cells (NKs), dendritic cells (DCs), macrophages, polymorphonuclear leukocytes, mast cells, and cytotoxic T lymphocytes (CTLs). Among them, NK cells are the predominant innate lymphocyte subsets that mediate antitumor and antiviral responses. The activation and inhibition of NK cells are regulated by cytokines and the balance between activating and inhibitory receptors. There is an inextricable regulatory relationship between macrophages and NK cells. Herein, we systematically elaborate on the regulatory network between macrophages and NK cells through soluble mediator crosstalk and cell-to-cell interactions. We believe that a better understanding of the crosstalk between macrophages and NKs in the TME will benefit the development of novel macrophage- or NK cell-focused therapeutic strategies with superior efficacies in cancer therapy.

Mesenchymal Stem Cell-Derived Exosomes: Applications in Regenerative Medicine

Exosomes are a type of extracellular vesicles, produced within multivesicular bodies, that are then released into the extracellular space through a merging of the multivesicular body with the plasma membrane. These vesicles are secreted by almost all cell types to aid in a vast array of cellular functions, including intercellular communication, cell differentiation and proliferation, angiogenesis, stress response, and immune signaling. This ability to contribute to several distinct processes is due to the complexity of exosomes, as they carry a multitude of signaling moieties, including proteins, lipids, cell surface receptors, enzymes, cytokines, transcription factors, and nucleic acids. The favorable biological properties of exosomes including biocompatibility, stability, low toxicity, and proficient exchange of molecular cargos make exosomes prime candidates for tissue engineering and regenerative medicine. Exploring the functions and molecular payloads of exosomes can facilitate tissue regeneration therapies and provide mechanistic insight into paracrine modulation of cellular activities. In this review, we summarize the current knowledge of exosome biogenesis, composition, and isolation methods. We also discuss emerging healing properties of exosomes and exosomal cargos, such as microRNAs, in brain injuries, cardiovascular disease, and COVID-19 amongst others. Overall, this review highlights the burgeoning roles and potential applications of exosomes in regenerative medicine.

Switched phenotypes of macrophages during the different stages of Schistosoma japonicum infection influenced the subsequent trends of immune responses

BACKGROUND

Macrophages play crucial roles in immune responses during the course of schistosomal infections.

METHODS

We currently investigated influence of immunocompetent changes in macrophages via microarray-based analysis, mRNA expression analysis, detection of serum cytokines, and subsequent evaluation of the immune phenotypes following the differentiation of infection-induced lymphocytes in a unique T1/T2 double-transgenic mouse model.

RESULTS

The gradual upregulation of genes encoding YM1, YM2, and interleukin (IL)-4/IL-13 receptors in infected mice indicated the role of type 2 alternatively activated macrophages (M2, AAMφs) in immune responses after Schistosoma japonicum egg production. FACS analysis showed that surface markers MHC class II (IA/IE) and CD8α⁺ of the macrophages also exhibited a dramatic change at the various time points before and after egg-production. The transgenic mouse experiments further demonstrated that the shifting of macrophage phenotypes influenced the percentage of helper T (Th)-2 cells, which was observed to be higher than that of Th1 cells, which increased only at 3 and 5 weeks post-infection. The differentiation of effector B cells showed a similar but more significant trend toward type-2 immunity.

CONCLUSION

These results suggest that the infection of mice with S. japonicum resulted in a final Th2- and Be2-skewed immune response. This may be due to phenotypic changes in the macrophages. The influence of alternatively activated macrophages was also activated by S. japonicum egg production. This study elucidated the existence of variations in immune mechanisms at the schistosome infection stages.

Interleukin-27 and Its Diverse Effects on Bacterial Infections

Innate and adaptive immune responses against pathogens are known to be carefully orchestrated by specific cytokines that initiate and down regulate immune cell functions from the initial infection through tissue repair and homeostasis. However, some cytokines, including interleukin-27, are expressed at multiple phases of the infection, such that their pro and anti-inflammatory functions have been difficult to interpret. As elucidation of specific cytokine functions throughout infection is central to our understanding of protective vs. susceptible immunity and return to homeostasis vs. prolonged inflammation leading to septic shock, here we review the literature on IL-27 signaling and the various functions of this heterodimeric ligand member of the IL-12 cytokine family. Canonically, IL-27 is produced by antigen-presenting cells, and is thought of as an immunostimulatory cytokine due to its capacity to induce Th1 differentiation. However, many studies have also identified various immunosuppressive effects of IL-27 signaling, including suppression of Th17 differentiation and induction of co-inhibitory receptors on T cells. Thus, the exact role of IL-27 in the context of infectious diseases remains a topic of debate and active research. Additionally, as recent interest has focused on clinical management of acute vs. chronic infections, and life-threatening "cytokine storm" from sepsis, we propose a hypothetical model to explain the biphasic role of IL-27 during the early and late phases of immune responses to reconcile its known pro and anti-inflammatory functions, which could be therapeutically regulated to improve patient outcomes of infection.

The Role of gp130 Cytokines in Tuberculosis

Protective immune responses to Mycobacterium tuberculosis (Mtb) infection substantially depend on a delicate balance within cytokine networks. Thus, immunosuppressive therapy by cytokine blockers, as successfully used in the management of various chronic inflammatory diseases, is often connected with an increased risk for tuberculosis (TB) reactivation. Hence, identification of alternative therapeutics which allow the treatment of inflammatory diseases without compromising anti-mycobacterial immunity remains an important issue. On the other hand, in the context of novel therapeutic approaches for the management of TB, host-directed adjunct therapies, which combine administration of antibiotics with immunomodulatory drugs, play an increasingly important role, particularly to reduce the duration of treatment. In both respects, cytokines/cytokine receptors related to the common receptor subunit gp130 may serve as promising target candidates. Within the gp130 cytokine family, interleukin (IL)-6, IL-11 and IL-27 are most explored in the context of TB. This review summarizes the differential roles of these cytokines in protection and immunopathology during Mtb infection and discusses potential therapeutic implementations with respect to the aforementioned approaches.

Decreased levels of interleukin 27 in the serum of vitiligo patients

BACKGROUND

Vitiligo is a common skin disorder in which melanocytes are destroyed by auto-reactive immune responses. The loss of melanocytes results in the appearance of depigmented areas in different parts of the body. Cytokines have remarkable roles in the pathogenesis of vitiligo, such as IL-1, IL-6, and TNF-α; interleukin 27 (IL-27) is a new member of the IL-6/IL-12 family, mainly released by activated antigen-presenting cells. IL-27 has been suggested to function as a pro-inflammatory as well as an anti-inflammatory cytokine. Altered concentrations of IL-27 have been shown in various auto-immune diseases such as multiple sclerosis, rheumatoid arthritis, and psoriasis. No studies have been conducted to determine the expression of this cytokine in vitiligo patients.

OBJECTIVE

The objective of this study was to determine the serum concentration of IL-27 in vitiligo patients and compare it with normal individuals.

METHODS

The serum concentration of IL-27 in 79 vitiligo patients was evaluated in comparison to 45 healthy controls using ELISA assay.

RESULTS

Results showed decreased concentration of IL-27 in vitiligo patients as compared with healthy subjects (p=0.026). Furthermore, no correlation between IL-27 concentrations and disease parameters such as vitiligo severity and the extension of the depigmented area was observed.

STUDY LIMITATION

A larger sample size would be more recommended for this study.

CONCLUSION

The reduction in the serum levels of IL-27 in vitiligo patients compared to normal subjects suggested the possible anti-inflammatory role of this cytokine in vitiligo. Thus, IL-27 may be considered as a new target for the manipulation of the immune system in vitiligo patients.

Loss of IL-27Rα Results in Enhanced Tubulointerstitial Fibrosis Associated with Elevated Th17 Responses

Clinical and experimental studies have established that immune cells such as alternatively activated (M2) macrophages and Th17 cells play a role in the progression of chronic kidney disease, but the endogenous pathways that limit these processes are not well understood. The cytokine IL-27 has been shown to limit immune-mediated pathology in other systems by effects on these cell types, but this has not been thoroughly investigated in the kidney. Unilateral ureteral obstruction was performed on wild-type and IL-27Rα^-/- mice. After 2 wk, kidneys were extracted, and the degree of injury was measured by hydroxyproline assay and quantification of neutrophil gelatinase-associated lipocalin mRNA. Immune cell infiltrate was evaluated by immunohistochemistry and flow cytometry. An anti-IL-17A mAb was subsequently administered to IL-27Rα^-/- mice every 2 d from day of surgery with evaluation as described after 2 wk. After unilateral ureteral obstruction, IL-27 deficiency resulted in increased tissue injury and collagen deposition associated with higher levels of chemokine mRNA and increased numbers of M2 macrophages. Loss of the IL-27Rα led to increased infiltration of activated CD4⁺ T cells that coproduced IL-17A and TNF-α, and blockade of IL-17A partially ameliorated kidney injury. Patients with chronic kidney disease had elevated serum levels of IL-27 and IL-17A, whereas expression of transcripts for the IL-27RA and the IL-17RA in the tubular epithelial cells of patients with renal fibrosis correlated with disease severity. These data suggest that endogenous IL-27 acts at several points in the inflammatory cascade to limit the magnitude of immune-mediated damage to the kidney.

AAV Mediated Delivery of Myxoma Virus M013 Gene Protects the Retina against Autoimmune Uveitis

Uveoretinitis is an ocular autoimmune disease caused by the activation of autoreactive T- cells targeting retinal antigens. The myxoma M013 gene is known to block NF-κB (Nuclear Factor kappa-light-chain-enhancer of activated B cells) and inflammasome activation, and its gene delivery has been demonstrated to protect the retina against lipopolysaccharide (LPS)-induced uveitis. In this report we tested the efficacy of M013 in an experimental autoimmune uveoretinitis (EAU) mouse model. B10RIII mice were injected intravitreally with AAV (adeno associated virus) vectors delivering either secreted GFP (sGFP) or sGFP-TatM013. Mice were immunized with interphotorecptor retinoid binding protein residues 161–180 (IRBP_161–180) peptide in complete Freund’s adjuvant a month later. Mice were evaluated by fundoscopy and spectral domain optical coherence tomography (SD-OCT) at 14 days post immunization. Eyes were evaluated by histology and retina gene expression changes were measured by reverse transcribed quantitative PCR (RT-qPCR). No significant difference in ERG or retina layer thickness was observed between sGFP and sGFP-TatM013 treated non-uveitic mice, indicating safety of the vector. In EAU mice, expression of sGFP-TatM013 strongly lowered the clinical score and number of infiltrative cells within the vitreous humor when compared to sGFP treated eyes. Retina structure was protected, and pro-inflammatory genes expression was significantly decreased. These results indicate that gene delivery of myxoma M013 could be of clinical benefit against autoimmune diseases.

Regulatory cytokine function in the respiratory tract

The respiratory tract is an important site of immune regulation; required to allow protective immunity against pathogens, while minimizing tissue damage and avoiding aberrant inflammatory responses to inhaled allergens. Several cell types work in concert to control pulmonary immune responses and maintain tolerance in the respiratory tract, including regulatory and effector T cells, airway and interstitial macrophages, dendritic cells and the airway epithelium. The cytokines transforming growth factor β, interleukin (IL-) 10, IL-27, and IL-35 are key coordinators of immune regulation in tissues such as the lung. Here, we discuss the role of these cytokines during respiratory infection and allergic airway disease, highlighting the critical importance of cellular source and immunological context for the effects of these cytokines in vivo.

The effects of CD14 and IL-27 on induction of endotoxin tolerance in human monocytes and macrophages

Upon repeated exposure to endotoxin or lipopolysaccharide (LPS), myeloid cells enter a refractory state called endotoxin tolerance as a homeostatic mechanism. In innate immune cells, LPS is recognized by co-receptors Toll-like receptor 4 (TLR4) and CD-14 to initiate an inflammatory response for subsequent cytokine production. One such cytokine, interleukin (IL)-27, is produced by myeloid cells in response to bacterial infection. In monocytes, IL-27 has proinflammatory functions such as up-regulating TLR4 expression for enhanced LPS-mediated cytokine production; alternatively, IL-27 induces inhibitory functions in activated macrophages. This study investigated the effects of IL-27 on the induction of endotoxin tolerance in models of human monocytes compared with macrophages. Our data demonstrate that IL-27 inhibits endotoxin tolerance by up-regulating cell surface TLR4 expression and soluble CD14 production to mediate stability of the surface LPS-TLR4-CD14 complex in THP-1 cells. In contrast, elevated basal expression of membrane-bound CD14 in phorbol 12-myristate 13-acetate (PMA)-THP-1 cells, primary monocytes, and primary macrophages may promote CD14-mediated endocytosis and be responsible for the preservation of an endotoxin-tolerized state in the presence of IL-27. Overall, the efficacy of IL-27 in inhibiting endotoxin tolerance in human THP-1 monocytes and PMA-THP-1 macrophages is affected by membrane-bound and soluble CD14 expression.

IL-27 amplifies cytokine responses to Gram-negative bacterial products and Salmonella typhimurium infection

Cytokine responses from monocytes and macrophages exposed to bacteria are of particular importance in innate immunity. Focusing on the impact of the immunoregulatory cytokine interleukin (IL)-27 on control of innate immune system responses, we examined human immune responses to bacterial products and bacterial infection by E. coli and S. typhimurium. Since the effect of IL-27 treatment in human myeloid cells infected with bacteria is understudied, we treated human monocytes and macrophages with IL-27 and either LPS, flagellin, or bacteria, to investigate the effect on inflammatory signaling and cytokine responses. We determined that simultaneous stimulation with IL-27 and LPS derived from E. coli or S. typhimurium resulted in enhanced IL-12p40, TNF-α, and IL-6 expression compared to that by LPS alone. To elucidate if IL-27 manipulated the cellular response to infection with bacteria, we infected IL-27 treated human macrophages with S. typhimurium. While IL-27 did not affect susceptibility to S. typhimurium infection or S. typhimurium-induced cell death, IL-27 significantly enhanced proinflammatory cytokine production in infected cells. Taken together, we highlight a role for IL-27 in modulating innate immune responses to bacterial infection.

Antenatal IL-1-dependent inflammation persists postnatally and causes retinal and sub-retinal vasculopathy in progeny

Antenatal inflammation as seen with chorioamnionitis is harmful to foetal/neonatal organ development including to eyes. Although the major pro-inflammatory cytokine IL-1β participates in retinopathy induced by hyperoxia (a predisposing factor to retinopathy of prematurity), the specific role of antenatal IL-1β associated with preterm birth (PTB) in retinal vasculopathy (independent of hyperoxia) is unknown. Using a murine model of PTB induced with IL-1β injection in utero, we studied consequent retinal and choroidal vascular development; in this process we evaluated the efficacy of IL-1R antagonists. Eyes of foetuses exposed only to IL-1β displayed high levels of pro-inflammatory genes, and a persistent postnatal infiltration of inflammatory cells. This prolonged inflammatory response was associated with: (1) a marked delay in retinal vessel growth; (2) long-lasting thinning of the choroid; and (3) long-term morphological and functional alterations of the retina. Antenatal administration of IL-1R antagonists - 101.10 (a modulator of IL-1R) more so than Kineret (competitive IL-1R antagonist) - prevented all deleterious effects of inflammation. This study unveils a key role for IL-1β, a major mediator of chorioamnionitis, in causing sustained ocular inflammation and perinatal vascular eye injury, and highlights the efficacy of antenatal 101.10 to suppress deleterious inflammation.

Differing Outcome of Experimental Autoimmune Encephalitis in Macrophage/Neutrophil- and T Cell-Specific gp130-Deficient Mice

gp130 cytokines are differentially involved in regulating the T helper (H) 17-driven pathogenesis of experimental autoimmune encephalomyelitis (EAE), the animal model of human multiple sclerosis. Interleukin (IL)-6 directly promotes the development of TH17 cells through the gp130/IL-6R complex. By contrast, IL-27 has been shown to suppress a TH17 immune response by gp130/IL-27R-alpha (α) receptor ligation. The IL-27-dependent regulation of a TH17 development could be mediated on the level of CD4 T cells. However, because IL-27 also suppresses the secretion of the TH17-driving cytokines IL-6 and IL-12/23p40 in accessory cells, TH17 immune responses may also be controlled by IL-27 on the level of macrophages and/or neutrophils. To analyze these opposing effects of gp130 engagement on the pathogenesis of EAE, we immunized CD4⁺ T cell-specific gp130-deficient (CD4cre^posgp130^loxP/loxP) and macrophage/neutrophil-specific gp130-deficient (LysMcre^posgp130^loxP/loxP) mice with the myelin-oligodendrocyte-glycoprotein peptide MOG_35-55. Whereas inflammatory immune responses, TH17 differentiation, and pathology in CD4cre^posgp130^loxP/loxP mice were mitigated, disease progression was eventually enhanced in LysMcre^posgp130^loxP/loxP mice. Exacerbated disease in MOG_35-55-immunized LysMcre^posgp130^loxP/loxP mice was associated with an elevated development of TH17 cells and increased infiltration of the central nervous system with leukocytes indicating a suppressive role of macrophage/neutrophil-gp130. To further prove IL-6 to be responsible for the control of inflammation during EAE through gp130 on macrophages/neutrophils, we immunized LysMcre^posIL-6R^loxP/loxP mice. In contrast to LysMcre^posgp130^loxP/loxP mice, neuropathology in MOG_35-55-immunized macrophage/neutrophil-specific IL-6R-deficient mice was not enhanced indicating that the alleviation of EAE through macrophage/neutrophil-gp130 is mediated independently of IL-6. Together, this different pathology in macrophage/neutrophil- and CD4 T cell-specific gp130-deficient mice suggests that gp130 cytokines modulate TH17 inflammation differentially by targeting distinct cell types.

The presence of interleukin-27 during monocyte-derived dendritic cell differentiation promotes improved antigen processing and stimulation of T cells

Dendritic cells (DCs) are potent antigen-presenting cells necessary to establish effective adaptive immune responses. The cytokine environment that exists at the time of DC differentiation may be an important but often ignored determinant in the phenotypic and functional properties of DCs. Interleukin-27 (IL-27) is a unique cytokine that has both inflammatory and immune suppressive activities. Although it can both promote and oppose activity of different T-cell subsets, mostly anti-inflammatory activity has been described toward macrophages and DCs. However, the specific effect of IL-27 during DC differentiation and how that may change the nature of the antigen-presenting cell has not been investigated. In this report, we show that IL-27 treatment during monocyte-derived DC differentiation enhanced the ability to process antigens and stimulate T-cell activity. DCs differentiated in the presence of IL-27 showed enhanced acidification of latex bead-containing phagosomes that was consistent with elevated expression of vacuolar-ATPases. This resulted in inhibition of intracellular growth of Staphylococcus aureus. In addition, the levels of MHC class II surface expression were higher in DCs differentiated in the presence of IL-27. Production of IL-12 was also significantly increased during S. aureus infection of IL-27-differentiated DCs. The net effect of these activities was enhanced CD4(+) T-cell proliferation and T helper type 1 cytokine production. These findings are important to a wide number of immunological contexts and should be considered in the development of future vaccines.

Analytical assessment of interleukin - 23 and -27 cytokines in healthy people and patients with hepatitis C virus infection (genotypes 1 and 3a)

BACKGROUND

The immune system plays important roles in determining the outcomes of hepatitis C virus (HCV) infection. Interleukin-23 and -27 (IL-23 and IL-27) are two novel IL-12 cytokine family members known to enhance the T-lymphocyte response, but their precise involvement in HCV infection is not well known.

OBJECTIVES

We investigated the serum IL-27 and IL-23 levels in patients with HCV infection and in healthy individuals.

PATIENTS AND METHODS

In this case-control study, we assessed IL-23 and IL-27 levels in serum of 37 healthy individuals and 64 patients with chronic HCV using Enzyme-linked immunosorbent assay (ELISA). The relationship of cytokines level with liver enzymes (ALT, AST, and ALP), HCV genotype and viral load were analyzed. The differences of these cytokine levels in the groups of treatment and no treatment was compared. HCV genotypes were classified by HCV-specific primers methods. HCV RNA loads were determined by fluorescence quantitative PCR.

RESULTS

Serum level of IL-23 was higher in HCV infected patients compared to control group (P = 0.005). However, no significant difference was seen in IL-27 serum level between patients compared to the control group (P = 0.65). There was no significant difference in IL-23 and IL-27 level between genotype 1 HCV-infected- and 3a HCV-infected- patients. Positive moderate correlation between IL-23 and IL-27 with viral load was found in type 3a and 1 HCV-infected patient. Positive relative correlation was seen between ALT and IL-23 in 1a HCV-infected patients, which was higher than 3a HCV-infected patients; but there were no significant difference between serums liver enzymes with IL-23 and IL-27 in respect to genotype 3a and 1a HCV-infected patients.

CONCLUSIONS

These findings may reflect a vigorous pro-inflammatory reaction orchestrated by the host immune system against chronic HCV. Also, a better understanding of the involvement mechanism considering the correlation between other genotypes with inflammatory cytokines in various stages of disease can be obtained.

Neonatal macrophages express elevated levels of interleukin-27 that oppose immune responses

Microbial infections are a major cause of infant mortality worldwide because of impaired immune defences in this population. The nature of this work was to further understand the mechanistic limitations of the neonatal and infant immune response. Interleukin-27 (IL-27) is a heterodimeric cytokine of the IL-12 family that is produced primarily by antigen-presenting cells and is immunosuppressive toward a variety of immune cell types. We show that IL-27 gene expression is elevated in cord blood-derived macrophages relative to macrophages originating from healthy adults. We also evaluated the duration over which elevated IL-27 gene expression may impact immune responses in mice. Age-dependent analysis of IL-27 gene expression indicated that levels of IL-27 remained significantly elevated throughout infancy and then declined in adult mice. Flow cytometric analysis of intracellular cytokine-stained splenocytes further confirmed these results. Interleukin-27 may be induced during pregnancy to contribute to the immunosuppressive environment at the fetal-maternal interface because we demonstrate dose-responsive gene expression to progesterone in macrophages. Neutralization of IL-27 in neonatal macrophages improved the ability of these cells to limit bacterial replication. Moreover, neutralization of IL-27 during incubation with the Mycobacterium bovis bacillus Calmette-Guérin vaccine augmented the level of interferon-γ elicited from allogeneic CD4+ T lymphocytes. This suggests that blocking IL-27 during vaccination and infection may improve immune responses in newborn and infant populations. Furthermore, mice will be a suitable model system to further address these possibilities.

The biology of nematode- and IL4Rα-dependent murine macrophage polarization in vivo as defined by RNA-Seq and targeted lipidomics

Alternatively activated macrophages (AAMϕ) are a major component of the response to helminth infection; however, their functions remain poorly defined. To better understand the helminth-induced AAMϕ phenotype, we performed a systems-level analysis of in vivo derived AAMϕ using an established mouse model. With next-generation RNA sequencing, we characterized the transcriptomes of peritoneal macrophages from BALB/c and IL4Rα(-/-) mice elicited by the nematode Brugia malayi, or via intraperitoneal thioglycollate injection. We defined expression profiles of AAMϕ-associated cytokines, chemokines, and their receptors, providing evidence that AAMϕ contribute toward recruitment and maintenance of eosinophilia. Pathway analysis highlighted complement as a potential AAMϕ-effector function. Up-regulated mitochondrial genes support in vitro evidence associating mitochondrial metabolism with alternative activation. We mapped macrophage transcription start sites, defining over-represented cis-regulatory motifs within AAMϕ-associated promoters. These included the binding site for PPAR transcription factors, which maintain mitochondrial metabolism. Surprisingly PPARγ, implicated in the maintenance of AAMϕ, was down-regulated on infection. PPARδ expression, however, was maintained. To explain how PPAR-mediated transcriptional activation could be maintained, we used lipidomics to quantify AAMϕ-derived eicosanoids, potential PPAR ligands. We identified the PPARδ ligand PGI(2) as the most abundant AAMϕ-derived eicosanoid and propose a PGI(2)-PPARδ axis maintains AAMϕ during B malayi implantation.

Interferon-γ, tumor necrosis factor, and interleukin-18 cooperate to control growth of Mycobacterium tuberculosis in human macrophages

Mycobacterium tuberculosis (MTB) remains a leading infectious threat to human health. Macrophages are the cells targeted for infection by the bacterium as well as key effector cells for clearance of the pathogen. Interleukin (IL)-27 opposes macrophage-mediated control of MTB because supplying IL-12 and blocking the activity of IL-27 limits bacterial growth in primary human macrophages. The purpose of this study was to determine the immunological regulators of this macrophage mechanism to restrict MTB growth. Interferon (IFN)-γ, TNF-α, and IL-18 were all demonstrated to be important to the environment that limits bacterial growth when IL-12 is supplied and IL-27 is neutralized. We find IL-18 works in conjunction with IL-12 to achieve optimal IFN-γ production in this system. We also demonstrate novel interactions between these cytokines to influence the expression or responsiveness to one another. Quantitative assays show that IFN-γ enhances expression of the IL-18 receptor signaling chain, as well as TNF expression and secretion. In turn, TNF-α augments expression of the receptor for IFN-γ, the amount at the cell surface, and the extent of IFN-γ -induced signaling. We further define how the cytokine environment supports an enhanced state of classical macrophage activation. Collectively, these results describe novel immunological mechanisms that provide additional insights into the effects of IL-12 and IL-27 on macrophage regulation during MTB infection.

IL-27-induced gene expression is downregulated in HIV-infected subjects

OBJECTIVE

To characterize the effect of HIV infection on IL-27-induced gene expression.

DESIGN

During HIV infection, cytokine expression and function become deregulated. IL-27 is an important modulator of inflammatory responses. Interestingly, IL-27 can inhibit HIV replication in T cells and monocytes, implicating IL-27 as a potential adjunct to anti-viral treatment. Our previous work demonstrated that circulating HIV may suppress IL-27 expression, therefore, this study, in continuation of our previous work, aimed to understand how HIV affects expression levels of the IL-27 receptor and downstream functions of IL-27.

METHODS

Peripheral blood mononuclear cells (PBMC) were isolated from whole blood of HIV negative and HIV positive (viremic) individuals to assess IL-27-induced gene expression by flow cytometry and ELISA. PBMC were also processed for monocyte enrichment to assess IL-27 receptor expression by flow cytometry and real-time PCR.

RESULTS

Expression of the IL-27 receptor subunit, gp130, was upregulated in response to IL-27 in HIV negative individuals, however, in HIV positive individuals, this IL-27 response was diminished. Furthermore, we observed downregulation of IL-27-induced IL-6, TNF-α, and IL-10 expression in HIV positive subjects.

CONCLUSION

In HIV infection, IL-27-induced gene expression was impaired, indicating HIV-mediated dysregulation of IL-27 functions occurs during HIV infection. This study provides evidence for new viral pathogenic mechanisms contributing to the widespread impairment of immune responses observed in HIV pathogenesis.

Cytokines, chemokines and growth factors in wound healing

In wound healing, a variety of mediators have been identified throughout the years. The mediators discussed here comprise growth factors, cytokines and chemokines. These mediators act via multiple (specific) receptors to facilitate wound closure. As research in the last years has led to many new findings, there is a need to give an overview on what is known, and on what might possibly play a role as a molecular target for future wound therapy. This review aims to keep the reader up to date with selected important and novel findings regarding growth factors, cytokines and chemokines in wound healing.

IL-27 enhances LPS-induced proinflammatory cytokine production via upregulation of TLR4 expression and signaling in human monocytes

IL-27, which is produced by activated APCs, bridges innate and adaptive immunity by regulating the development of Th cells. Recent evidence supports a role for IL-27 in the activation of monocytic cells in terms of inflammatory responses. Indeed, proinflammatory and anti-inflammatory activities are attributed to IL-27, and IL-27 production itself is modulated by inflammatory agents such as LPS. IL-27 primes LPS responses in monocytes; however, the molecular mechanism behind this phenomenon is not understood. In this study, we demonstrate that IL-27 priming results in enhanced LPS-induced IL-6, TNF-α, MIP-1α, and MIP-1β expression in human primary monocytes. To elucidate the molecular mechanisms responsible for IL-27 priming, we measured levels of CD14 and TLR4 required for LPS binding. We determined that IL-27 upregulates TLR4 in a STAT3- and NF-κB-dependent manner. Immunofluorescence microscopy revealed enhanced membrane expression of TLR4 and more distinct colocalization of CD14 and TLR4 upon IL-27 priming. Furthermore, IL-27 priming enhanced LPS-induced activation of NF-κB family members. To our knowledge, this study is the first to show a role for IL-27 in regulating TLR4 expression and function. This work is significant as it reveals new mechanisms by which IL-27 can enhance proinflammatory responses that can occur during bacterial infections.

M2 polarized macrophages and giant cells contribute to myofibrosis in neuromuscular sarcoidosis

The etiopathogenesis of sarcoidosis, a systemic granulomatous disease, still remains obscure. A multitude of organs have been described to be affected in systemic sarcoidosis. Skeletal muscles may also be affected, leading to myalgia and weakness. A workup of the specific immune response with emphasis on the macrophage response is provided herein. Affected muscle tissue from seven patients with systemic sarcoidosis was analyzed and compared with that from seven patients with other myopathies containing macrophagocytic infiltration. Monocytes/macrophages and giant cells in granulomas of muscle tissue from patients with sarcoidosis show a status of alternative activation (M2) based on their expression of CD206, CD301, arginase-1, and suppressor of cytokine signaling-1 as a consequence of a functionally type 2 helper T cell (Th2)-biased cytokine profile. Significant fibrosis and up-regulation of CCL18 were associated with the M2 phenotype of macrophages. Conversely, up-regulated Th1 cytokines did not result in significant classical activation of macrophages (M1), with poor inducible nitric oxide synthase and cyclooxygenase-2 production. Giant cell formation was further associated with up-regulated expression of DNAX-activating protein of 12 kDa (DAP12; gene symbol TYROBP). Functionally, alternative activation of macrophages on the basis of a Th2-biased immune response may induce clinical symptoms and chronic evolution of neuromuscular sarcoidosis. This is the first characterization of Th2-mediated immune mechanisms in neuromuscular sarcoidosis suggesting that a specific macrophage activation status leading to myofibrosis may be a key event in the pathogenesis of this disease.

gp130 on macrophages/granulocytes modulates inflammation during experimental tuberculosis

gp130 is a common receptor chain for cytokines such as interleukin (IL)-27 and IL-6. During experimental tuberculosis (TB), IL-27 prevents optimal antimycobacterial protection and limits the pathological sequelae of chronic inflammation. The anti-inflammatory properties of IL-27 have been attributed mainly to its suppressive effect on T helper (TH) cells. However, because gp130 cytokines also suppress the inflammatory immune response of macrophages, IL-27 may also regulate inflammation by limiting the secretion of pro-inflammatory cytokines. To specifically address the role of gp130 cytokines on macrophages, the outcome of experimental TB was analysed in macrophage/neutrophil-specific gp130-deficient (LysM(cre) gp130(loxP/loxP)) mice. In these mice, the enhanced induction of inflammatory cytokines and increased expression of the inducible nitric oxide synthase (NOS2) and LRG47 was linked to a greatly augmented TH17 immune response and matrix metalloproteinase (MMP)-9 expression. However, this amplified inflammatory immune response in Mtb-infected LysM(cre) gp130(loxP/loxP) mice was not associated with reduced bacterial loads and/or accelerated pathology. Our study revealed an immunoregulatory function of gp130 cytokines on macrophages/granulocytes, which is, however, not critical for modulating the outcome of TB.

IL-27/IFN-γ induce MyD88-dependent steroid-resistant airway hyperresponsiveness by inhibiting glucocorticoid signaling in macrophages

Inflammation and airway hyperresponsiveness (AHR) are hallmark features of asthma and often correlate with the severity of clinical disease. Although these features of asthma can be effectively managed with glucocorticoid therapy, a subgroup of patients, typically with severe asthma, remains refractory to therapy. The mechanisms leading to steroid resistance in severe asthmatics are poorly understood but may be related to the activation of innate host defense pathways. Previously, we have shown that IFN-γ-producing cells and LPS, two factors that are associated with severe asthma, induce steroid-resistant AHR in a mouse model. We now demonstrate that cooperative signaling induced by IFN-γ and LPS results in the production of IL-27 by mouse pulmonary macrophages. IL-27 and IFN-γ uniquely cooperate to induce glucocorticoid-resistant AHR through a previously unknown MyD88-dependent mechanism in pulmonary macrophages. Importantly, integrated signaling by IL-27/IFN-γ inhibits glucocorticoid-induced translocation of the glucocorticoid receptor to the nucleus of macrophages. Furthermore, expression of both IL-27 and IFN-γ was increased in the induced sputum of steroid-refractory asthmatics. These results suggest that a potential mechanism for steroid resistance in asthma is the activation of MyD88-dependent pathways in macrophages that are triggered by IL-27 and IFN-γ, and that manipulation of these pathways may be a therapeutic target.

Essential role for IL-27 receptor signaling in prevention of Th1-mediated immunopathology during malaria infection

Successful resolution of malaria infection requires induction of proinflammatory immune responses that facilitate parasite clearance; however, failure to regulate this inflammation leads to immune-mediated pathology. The pathways that maintain this immunological balance during malaria infection remain poorly defined. In this study, we demonstrate that IL-27R-deficient (WSX-1(-/-)) mice are highly susceptible to Plasmodium berghei NK65 infection, developing exacerbated Th1-mediated immune responses, which, despite highly efficient parasite clearance, lead directly to severe liver pathology. Depletion of CD4(+) T cells---but not CD8(+) T cells---prevented liver pathology in infected WSX-1(-/-) mice. Although WSX-1 signaling was required for optimal IL-10 production by CD4(+) T cells, administration of rIL-10 failed to ameliorate liver damage in WSX-1(-/-) mice, indicating that additional, IL-10-independent, protective pathways are modulated by IL-27R signaling during malaria infection. These data are the first to demonstrate the essential role of IL-27R signaling in regulating effector T cell function during malaria infection and reveal a novel pathway that might be amenable to manipulation by drugs or vaccines.

Interleukin-27 induces a STAT1/3- and NF-kappaB-dependent proinflammatory cytokine profile in human monocytes

IL-27 is a heterodimeric cytokine bridging innate and adaptive immunity by playing a role in the activation of naive T cells and in development of Th1 cells. Additionally, recent evidence supports a role for IL-27 in the activation of monocytic cells. Both pro-inflammatory and anti-inflammatory activities have been attributed to IL-27; however, the role played by IL-27 in the activation of human monocytic cells in terms of cytokine production has not been well described. Our results show that IL-27 is a strong inducer of proinflammatory cytokine and chemokine expression, including enhancement of IL-6, IP-10, MIP-1alpha, MIP-1beta, and TNF-alpha expression in human primary monocytes. Furthermore, we observed that IL-27-induced cytokine and chemokine production was mediated by STAT1, STAT3, and NF-kappaB activation. Understanding how IL-27 exerts its effects on monocytic cells will identify important molecular mechanisms in the regulation of immune responses, particularly in the modulation of monocyte activation.

Impact of HIV infection, highly active antiretroviral therapy, and hepatitis C coinfection on serum interleukin-27

A newly described cytokine, interleukin-27 (IL-27), that activates naive CD4 T cells, has recently been shown to be an anti-HIV cytokine. However, the effect of HIV infection on IL-27 expression has not been characterized. We found that clinical characteristics, including HIV viral load, hepatitis C virus coinfection, and CD4 T cell counts, were associated with changes in serum IL-27. Overall, our results suggest circulating HIV may suppress IL-27, a critical concept in treatment development with this cytokine.

Differential effect of IL-27 on developing versus committed Th17 cells

IL-27 counters the effect of TGF-beta+IL-6 on naive CD4(+) T cells, resulting in near complete inhibition of de novo Th17 development. In contrast, little is known about the effect of IL-27 on already differentiated Th17 cells. A better understanding of how IL-27 regulates these cells is needed to evaluate the therapeutic potential of IL-27 in Th17 cells-associated diseases. In this study, we show that IL-27 had surprisingly little effect on committed Th17 cells, despite its expression of a functional IL-27R. Contrary to de novo differentiation of Th17 cells, IL-27 did not suppress expression of retinoid-related orphan receptor (ROR)gammat or RORalpha in committed Th17 cells. Consistent with this finding, the frequency of committed Th17 cells and their cytokine secretion remained unaffected by IL-27. Both memory Th17 cells (CD4(+)CD25(-)CD62L(low)) that developed in vivo and encephalitogenic Th17 cells infiltrating the CNS of mice developing experimental autoimmune encephalomyelitis produced similar amounts of IL-17A when reactivated with IL-23 in the absence and presence of exogenous IL-27. Finally, IL-27 failed to suppress encephalitogenicity of Th17 cells in an adoptive transfer of experimental autoimmune encephalomyelitis. Analysis ex vivo of transferred Th17 cells in the spleen and CNS of recipient mice showed that cells retained similar phenotype irrespective of whether cells were treated or not with IL-27. Our data demonstrate that in contrast to inhibition of de novo differentiation of Th17 cells, IL-27 has little or no effect on committed Th17 cells. These findings indicate that therapeutic applications of IL-27 might have a limited efficacy in inflammatory conditions where aggressive Th17 responses have already developed.

IL-27 is expressed in chronic human eczematous skin lesions and stimulates human keratinocytes

BACKGROUND

IL-27 is produced by antigen-presenting cells early during immune responses. IL-27 has been described to support T-cell polarization along the T(H)1 lineage but also to exert important anti-inflammatory responses in later phases of inflammation in murine models.

OBJECTIVE

It was the aim of this study to analyze the potential role of IL-27 in epidermal inflammatory skin responses in human subjects.

METHODS

Surface receptor expression and apoptosis of human primary keratinocytes were analyzed by means of flow cytometry. Supernatants of stimulated keratinocytes were either analyzed by means of ELISA or submitted to chemotaxis assays. RT-PCR from lesional skin and phospho-specific Western blotting were performed.

RESULTS

Both subunits of IL-27 were expressed in chronic lesional allergic eczematous skin, whereas the IL-27 subunit EBV-induced gene 3 was not detectable in the acute phase of eczema. Human primary keratinocytes responded to IL-27. Stimulation of keratinocytes with IL-27 resulted in activation of the signal transducer and activator of transcription 1 and 3 pathways. Major effects found for IL-27 include CXCL10 production and MHC class I upregulation. Importantly, we could demonstrate that IL-27 acts as a priming signal on keratinocytes able to amplify chemokine production and surface molecule expression when used before a second signal, such as TNF-alpha. The effects of IL-27 could not be mimicked by IL-6, IL-12, or IL-23.

CONCLUSION

These results support the notion that IL-27 might act in an inflammatory, disease-maintaining manner in the epidermal compartment of patients with eczema.

Alternative activation of macrophages: immune function and cellular biology

Macrophages are the first line of defense of the organism against pathogens and, in response to the microenvironment, become differentially activated. In the presence of IL-4 and IL-13, cytokines that are produced in a Th-2 type response, particularly during allergy and parasitic infections, macrophages become differentially activated. Alternative activated macrophages play an important role in the protection of the host by decreasing inflammation and promoting tissues repair. However, alternative activation of macrophages also downregulates host protection against selected pathogens. This defect is associated with an altered receptor expression pattern and extensive modulation of intracellular membrane trafficking. This review shows how alternative activation of macrophages induces extensive cellular remodelling of phagocytic, endocytic, signaling and secretory pathways which play an important, but unclear role in the pathogenesis of different disease.

Regulation of immune responses by interleukin-27

Cytokine-mediated immunity plays a crucial role in the pathogenesis of various diseases including autoimmunity. Recently, interleukin-27 (IL-27) was identified, which, along with IL-12, IL-23, and IL-35, belongs to the IL-12 cytokine family. These family members play roles in the regulation of T helper (Th) cell differentiation. IL-27 is unique in that while it induces Th1 differentiation, the same cytokine suppresses immune responses. In the absence of IL-27-mediated immunosuppression, hyper-production of various pro-inflammatory cytokines concomitant with severe inflammation in affected organs was observed in IL-27 receptor alpha chain (WSX-1)-deficient mice infected with Trypanosoma cruzi. Experimental allergic or inflammatory responses were also enhanced in WSX-1-deficient mice. The immunosuppressive effects of IL-27 depend on inhibition of the development of Th17 cells (a newly identified inflammatory T-helper population) and induction of IL-10 production. Moreover, administration of IL-27 or augmentation of IL-27 signaling suppresses some diseases of autoimmune or allergic origin, demonstrating its potential in therapy of diseases mediated by inflammatory cytokines. In this review, we discuss recent studies on the role of IL-27 in immunity to parasitic and bacterial infections as well as in allergy and autoimmunity in view of its pro- and anti-inflammatory properties.

Analyzing classical and alternative macrophage activation in macrophage/neutrophil-specific IL-4 receptor-alpha-deficient mice

Macrophage activation can be divided into a classical and an alternative pathway. Interferon-gamma-induced, classically activated macrophages are indispensable for protective effector responses against intracellular pathogens. However, excessive inflammatory immune responses mediated by classical macrophage activation can also be detrimental to the host. In contrast, the IL-4 receptor-alpha-mediated alternative pathway of macrophage activation has been proposed as a mechanism to attenuate excessive inflammation. Indeed, the generation of macrophage/neutrophil-specific IL-4 receptor-alpha-deficient mice (LysMcreIL-4Ralphaalpha-/lox) enables us now to evaluate the importance of this type of macrophage activation in vivo. Thus, the analysis of LysMcreIL-4Ralpha-/lox mice and the phenotypic characterization of macrophage activation during inflammatory immune responses become of major importance for inflammation research, and useful markers have been identified that allow classically and alternatively activated macrophages to be distinguished. Inducible nitric oxide synthase and arginase-1 are not only prototypical markers of classical and alternative macrophage activation, but both enzymes are also strongly involved in regulating macrophage effector mechanisms and inflammatory immune responses. In this chapter, we describe the use of LysMcreIL-4Ralpha-/lox mice and present experimental procedures to determine classical versus alternative macrophage activation by analyzing nitric oxide synthase and arginase-1 in vitro and in vivo in this murine model.

Exploring the full spectrum of macrophage activation

Macrophages display remarkable plasticity and can change their physiology in response to environmental cues. These changes can give rise to different populations of cells with distinct functions. In this Review we suggest a new grouping of macrophage populations based on three different homeostatic activities - host defence, wound healing and immune regulation. We propose that similarly to primary colours, these three basic macrophage populations can blend into various other 'shades' of activation. We characterize each population and provide examples of macrophages from specific disease states that have the characteristics of one or more of these populations.

IL-27 activates human monocytes via STAT1 and suppresses IL-10 production but the inflammatory functions of IL-27 are abrogated by TLRs and p38

IL-27 is a member of the IL-12 family of cytokines that activates the Jak-STAT signaling pathway in a context-dependent manner and has pleiotropic effects on acquired immunity. IL-27 has the capacity to promote early stages of Th1 generation, but recent evidence has suggested a predominant suppressive effect on Th1, Th2, and Th17 differentiation. Although modest suppressive effects of IL-27 on myeloid lineage cells have been observed, there is limited knowledge about the role of IL-27 in the regulation of innate immunity. In this study we report that although in resting murine macrophages IL-27 had minimal if any effects, in resting human monocytes IL-27 had profound proinflammatory functions. IL-27 activated a STAT1-dominant pattern of signaling in human monocytes with the consequent activation of STAT1-dependent inflammatory target genes. IL-27 primed monocytes for augmented responses to TLR stimulation in a STAT1-dependent manner, altered IL-10 signaling, and attenuated IL-10-induced gene expression. Strikingly, IL-27 strongly suppressed TLR-induced IL-10 production in human monocytes. However, the proinflammatory effects of IL-27 on human monocytes were rapidly abrogated by LPS via a p38-mediated mechanism that inhibited IL-27 signaling. Our findings identify a predominantly proinflammatory function for IL-27 in human monocytes and suggest a mechanism by which the activating effects of IL-27 on innate immunity are attenuated as an immune response proceeds and IL-27 transitions to predominantly suppressive effects on acquired immunity.

Advances in understanding the anti-inflammatory properties of IL-27

Initial studies on the biology of IL-27 provided evidence of a role for this cytokine in the initiation of Th1 responses; however, subsequent work using models of pathogen-induced and autoimmune inflammation have indicated that IL-27 has broad inhibitory effects on Th1, Th2 and Th17 subsets of T cells as well as the expansion of inducible regulatory T cells. While, the aim of this review is to highlight the functions of IL-27 in the context of inflammation it will also serve to elaborate on the molecular mechanisms involved in the production of this cytokine. The initial description of IL-27 indicated that classical antigen-presenting cells such as macrophages and dendritic cells produce IL-27, however, the agonists and signaling pathways involved in activating transcription of the two subunits of IL-27, p28 and EBV-induced gene 3 (EBI3) have only recently been described.

Alternatively activated macrophages in helminth infections

Helminthic parasites can trigger highly polarized immune responses typically associated with increased numbers of CD4(+) Th2 cells, eosinophils, mast cells, and basophils. These cell populations are thought to coordinate an effective response ultimately leading to parasite expulsion, but they also play a role in the regulation of associated pathologic inflammation. Recent studies suggest that macrophages, conventionally associated with IFN-gamma-dominant Th1-type responses to many bacteria and viruses, also play an essential role in the Th2-type inflammatory response. These macrophages are referred to as alternatively activated macrophages (AAMPhis) as they express a characteristic pattern of cell surface and secreted molecules distinct from that of classically activated macrophages (CAMPhis) associated with microbe infections. In this review, we will discuss recent findings regarding the role of AAMPhis in the development of disease and host protection following helminth infection.

Regulation of defense responses against protozoan infection by interleukin-27 and related cytokines

Cytokine-mediated immunity is crucial in the defense against pathogens. Recently, IL-23 and IL-27 were identified, which along with IL-12 belong to the IL-12 cytokine family. IL-27 is pivotal for the induction of helper T cell (Th) 1 responses while IL-23 is important for the proliferation of memory type Th1 cells. Recent studies revealed that IL-27 also has an anti-inflammatory property. In some protozoan infection, various proinflammatory cytokines were over produced causing lethal inflammatory responses in IL-27 receptor-deficient mice. The anti-inflammatory effect of IL-27 depends, at least partly, on inhibition of the development of Th17 cells, a newly identified Th population that is induced by IL-23 and is characterized by the production of the inflammatogenic cytokine, IL-17. IL-27 thus has a double identity as an initiator and as an attenuator of immune responses and inflammation. With the discoveries of the new IL-12-related cytokines and Th17 cells, Th development is facing a new paradigm.

The biology and therapeutic potential of interleukin 27

Interleukin (IL-) 27 is a helical cytokine of the greater IL-6/IL-12 family with a broad range of pro- and anti-inflammatory properties. It can skew T helper cell development, suppress T cell proliferation, stimulate cytotoxic T cell activity, induce isotype switching in B cells, and has diverse effects on innate immune cells. In vivo, its most important role appears to be that of immune regulation, as mice with defects in IL-27 or its receptor display enhanced immune responses in a range of infectious and noninfectious situations. In this review, we discuss the body of knowledge on IL-27 and its potential therapeutic utility.