Plasmodium berghei ANKA (PbA) infection of C57BL/6 mice leads to experimental cerebral malaria (ECM) that is commonly associated with serious T cell mediated damage. In other parasitic infection ...models, inflammatory monocytes have been shown to regulate Th1 responses but their role in ECM remains poorly defined, whereas neutrophils are reported to contribute to ECM immune pathology. Making use of the recent development of specific monoclonal antibodies (mAb), we depleted in vivo Ly6C(hi) inflammatory monocytes (by anti-CCR2), Ly6G+ neutrophils (by anti-Ly6G) or both cell types (by anti-Gr1) during infection with Ovalbumin-transgenic PbA parasites (PbTg). Notably, the application of anti-Gr1 or anti-CCR2 but not anti-Ly6G antibodies into PbTg-infected mice prevented ECM development. In addition, depletion of Ly6C(hi) inflammatory monocytes but not neutrophils led to decreased IFNγ levels and IFNγ+CD8+ T effector cells in the brain. Importantly, anti-CCR2 mAb injection did not prevent the generation of PbTg-specific T cell responses in the periphery, whereas anti-Gr1 mAb injection strongly diminished T cell frequencies and CTL responses. In conclusion, the specific depletion of Ly6C(hi) inflammatory monocytes attenuated brain inflammation and immune cell recruitment to the CNS, which prevented ECM following Plasmodium infection, pointing out a substantial role of Ly6C+ monocytes in ECM inflammatory processes.
Malaria ranks among the most important infectious diseases worldwide and affects mostly people living in tropical countries. Mechanisms involved in disease progression are still not fully understood ...and specific treatments that might interfere with cerebral malaria (CM) are limited. Here we show that administration of doxycycline (DOX) prevented experimental CM (ECM) in Plasmodium berghei ANKA (PbA)-infected C57BL/6 wildtype (WT) mice in an IL-10-independent manner. DOX-treated mice showed an intact blood-brain barrier (BBB) and attenuated brain inflammation. Importantly, if WT mice were infected with a 20-fold increased parasite load, they could be still protected from ECM if they received DOX from day 4-6 post infection, despite similar parasitemia compared to control-infected mice that did not receive DOX and developed ECM. Infiltration of T cells and cytotoxic responses were reduced in brains of DOX-treated mice. Analysis of brain tissue by RNA-array revealed reduced expression of chemokines and tumour necrosis factor (TNF) in brains of DOX-treated mice. Furthermore, DOX-administration resulted in brains of the mice in reduced expression of matrix metalloproteinase 2 (MMP2) and granzyme B, which are both factors associated with ECM pathology. Systemic interferon gamma production was reduced and activated peripheral T cells accumulated in the spleen in DOX-treated mice. Our results suggest that DOX targeted inflammatory processes in the central nervous system (CNS) and prevented ECM by impaired brain access of effector T cells in addition to its anti-parasitic effect, thereby expanding the understanding of molecular events that underlie DOX-mediated therapeutic interventions.
Postoperative ileus (POI) is an inflammation-mediated complication of abdominal surgery, characterized by intestinal dysmotility and leukocyte infiltration into the muscularis externa (ME). Previous ...studies indicated that interleukin (IL)-10 is crucial for the resolution of a variety of inflammation-driven diseases. Herein, we investigated how IL-10 affects the postoperative ME inflammation and found an unforeseen role of IL-10 in POI.
POI was induced by a standardized intestinal manipulation (IM) in C57BL/6 and multiple transgenic mouse strain including C-C motif chemokine receptor 2
, IL-10
, and LysM
/IL-10
mice. Leukocyte infiltration, gene and protein expression of cytokines, chemokines, and macrophage differentiation markers as well as intestinal motility were analyzed. IL-10 serum levels in surgical patients were determined by ELISA.
IL-10 serum levels were increased in patient after abdominal surgery. In mice, a complete or leucocyte-restricted IL-10 deficiency ameliorated POI and reduced the postoperative ME neutrophil infiltration. Infiltrating monocytes were identified as main IL-10 producers and undergo IL-10-dependent M2 polarization. Interestingly, M2 polarization is not crucial to POI development as abrogation of monocyte infiltration did not prevent POI due to a compensation of the IL-10 loss by resident macrophages and neutrophils. Organ culture studies demonstrated that IL-10 deficiency impeded neutrophil migration toward the surgically traumatized ME. This mechanism is mediated by reduction of neutrophil attracting chemokines.
Monocyte-derived macrophages are the major IL-10 source during POI. An IL-10 deficiency decreases the postoperative expression of neutrophil-recruiting chemokines, consequently reduces the neutrophil extravasation into the postsurgical bowel wall, and finally protects mice from POI.
Group 2 innate lymphoid cells (ILC2s) are inducers of type 2 immune responses, but their role during filarial infection remains unclear. In the present study, we used the
Litomosoides sigmodontis
...rodent model of filariasis to analyze ILC2s during infection in susceptible BALB/c mice that develop a chronic infection with microfilaremia and semi-susceptible C57BL/6 mice that eliminate the filariae shortly after the molt into adult worms and thus do not develop microfilaremia. ILC2s (CD45
+
Lineage
-
TCRβ
-
CD90.2
+
Sca-1
+
IL-33R
+
GATA-3
+
) were analyzed in the pleural cavity, the site of
L. sigmodontis
infection, after the infective L3 larvae reached the pleural cavity (9 days post infection, dpi), after the molt into adult worms (30dpi) and during the peak of microfilaremia (70dpi). C57BL/6 mice had significantly increased ILC2 numbers compared to BALB/c mice at 30dpi, accompanied by substantially higher IL-5 and IL-13 levels, indicating a stronger type 2 immune response in C57BL/6 mice upon
L. sigmodontis
infection. At this time point the ILC2 numbers positively correlated with the worm burden in both mouse strains. ILC2s and GATA-3
+
CD4
+
T cells were the dominant source of IL-5 in
L. sigmodontis
-infected C57BL/6 mice with ILC2s showing a significantly higher IL-5 expression than CD4
+
T cells. To investigate the importance of ILC2s during
L. sigmodontis
infection, ILC2s were depleted with anti-CD90.2 antibodies in T and B cell-deficient
Rag2
-/-
C57BL/6 mice on 26-28dpi and the outcome of infection was compared to isotype controls.
Rag2
-/-
mice were per se susceptible to
L. sigmodontis
infection with significantly higher worm burden than C57BL/6 mice and developed microfilaremia. Depletion of ILC2s did not result in an increased worm burden in
Rag2
-/-
mice, but led to significantly higher microfilariae numbers compared to isotype controls. In conclusion, our data demonstrate that ILC2s are essentially involved in the control of microfilaremia in
Rag2
-/-
C57BL/6 mice.
During blood-stage malaria, the innate immune system initiates the production of pro-inflammatory cytokines, including IFN-γ, that are critical to host defense and responsible for severe disease. ...Nonetheless, the innate immune pathways activated during this process in human malaria remain poorly understood. Here, we identify TLR8 as an essential sensor of
-infected red blood cells (iRBC). In human immune cells, iRBC and RNA purified from iRBC were detected by TLR8 but not TLR7 leading to IFN-γ induction in NK cells. While TLR7 and 9 have been shown to lead to IFN-γ in mice, our data demonstrate that TLR8 was the only TLR capable of inducing IFN-γ release in human immune cells. This unique capacity was mediated by the release of IL-12p70 and bioactive IL-18 from monocytes, the latter via a hitherto undescribed pathway. Altogether, our data are the first reported activation of TLR8 by protozoan RNA and demonstrate both the critical role of TLR8 in human blood-stage malaria and its unique functionality in the human immune system. Moreover, our study offers important evidence that mouse models alone may not be sufficient to describe the human innate immune response to malaria.
Background Aryl hydrocarbon receptor (AHR)-deficient mice do not support the expansion of dendritic epidermal T cells (DETC), a resident immune cell population in the murine epidermis, which ...immigrates from the fetal thymus to the skin around birth. Material and Methods In order to identify the gene expression changes underlying the DETC disappearance in AHR-deficient mice, we analyzed microarray RNA-profiles of DETC, sorted from the skin of two-week-old AHR-deficient mice and their heterozygous littermates. In vitro studies were done for verification, and IL-10, AHR repressor (AHRR), and c-Kit deficient mice analyzed for DETC frequency. Results We identified 434 annotated differentially expressed genes. Gene set enrichment analysis demonstrated that the expression of genes related to proliferation, ion homeostasis and morphology differed between the two mouse genotypes. Importantly, with 1767 pathways the cluster-group "inflammation" contained the majority of AHR-dependently regulated pathways. The most abundant cluster of differentially expressed genes was "inflammation." DETC of AHR-deficient mice were inflammatory active and had altered calcium and F-actin levels. Extending the study to the AHRR, an enigmatic modulator of AHR-activity, we found approximately 50% less DETC in AHRR-deficient mice than in wild-type-littermates. Conclusion AHR-signaling in DETC dampens their inflammatory default potential and supports their homeostasis in the skin.
Dendritic cells (DCs) are pivotal for the development of experimental autoimmune encephalomyelitis (EAE). However, the mechanisms by which they control disease remain to be determined. This study ...demonstrates that expression of CC chemokine receptor 4 (CCR4) by DCs is required for EAE induction. CCR4–/– mice presented enhanced resistance to EAE associated with a reduction in IL-23 and GM-CSF expression in the CNS. Restoring CCR4 on myeloid cells in bone marrow chimeras or intracerebral microinjection of CCR4-competent DCs, but not macrophages, restored EAE in CCR4–/– mice, indicating that CCR4+ DCs are cellular mediators of EAE development. Mechanistically, CCR4–/– DCs were less efficient in GM-CSF and IL-23 production and also TH-17 maintenance. Intraspinal IL-23 reconstitution restored EAE in CCR4–/– mice, whereas intracerebral inoculation using IL-23–/– DCs or GM-CSF–/– DCs failed to induce disease. Thus, CCR4-dependent GM-CSF production in DCs required for IL-23 release in these cells is a major component in the development of EAE. Our study identified a unique role for CCR4 in regulating DC function in EAE, harboring therapeutic potential for the treatment of CNS autoimmunity by targeting CCR4 on this specific cell type.
Skeletal muscle injury causes a local sterile inflammatory response. In parallel, a state of immunosuppression develops distal to the site of tissue damage. Granulocytes and monocytes that are ...rapidly recruited to the site of injury contribute to tissue regeneration. In this study we used a mouse model of traumatic skeletal muscle injury to investigate the previously unknown role of dendritic cells (DCs) that accumulate in injured tissue. We injected the model antigen ovalbumin (OVA) into the skeletal muscle of injured or sham-treated mice to address the ability of these DCs in antigen uptake, migration, and specific T cell activation in the draining popliteal lymph node (pLN). Immature DC-like cells appeared in the skeletal muscle by 4 days after injury and subsequently acquired a mature phenotype, as indicated by increased expression of the costimulatory molecules CD40 and CD86. After the injection of OVA into the muscle, OVA-loaded DCs migrated into the pLN. The migration of DC-like cells from the injured muscle was enhanced in the presence of the microbial stimulus lipopolysaccharide at the site of antigen uptake and triggered an increased OVA-specific T helper cell type 1 (Th1) response in the pLN. Naïve OVA-loaded DCs were superior in Th1-like priming in the pLN when adoptively transferred into the skeletal muscle of injured mice, a finding indicating the relevance of the microenvironment in the regenerating skeletal muscle for increased Th1-like priming. These findings suggest that DC-like cells that accumulate in the regenerating muscle initiate a protective immune response upon microbial challenge and thereby overcome injury-induced immunosuppression.
Cerebral malaria is a potentially lethal disease, which is caused by excessive inflammatory responses to
parasites. Here we use a newly developed transgenic
ANKA (
) parasite that can be used to ...study parasite-specific T cell responses. Our present study demonstrates that
mice, which lack type I interferon receptor-dependent signaling, are protected from experimental cerebral malaria (ECM) when infected with this novel parasite. Although CD8
T cell responses generated in the spleen are essential for the development of ECM, we measured comparable parasite-specific cytotoxic T cell responses in ECM-protected
mice and wild type mice suffering from ECM. Importantly, CD8
T cells were increased in the spleens of ECM-protected
mice and the blood-brain-barrier remained intact. This was associated with elevated splenic levels of CCL5, a T cell and eosinophil chemotactic chemokine, which was mainly produced by eosinophils, and an increase in eosinophil numbers. Depletion of eosinophils enhanced CD8
T cell infiltration into the brain and increased ECM induction in
-infected
mice. However, eosinophil-depletion did not reduce the CD8
T cell population in the spleen or reduce splenic CCL5 concentrations. Our study demonstrates that eosinophils impact CD8
T cell migration and proliferation during
-infection in
mice and thereby are contributing to the protection from ECM.
Inactivated orf virus (iORFV), strain D1701, is a potent immune modulator in various animal species. We recently demonstrated that iORFV induces strong antiviral activity in animal models of acute ...and chronic viral infections. In addition, we found D1701-mediated antifibrotic effects in different rat models of liver fibrosis. In the present study, we compare iORFV derived from two different strains of ORFV, D1701 and NZ2, respectively, with respect to their antifibrotic potential as well as their potential to induce an antiviral response controlling infections with the hepatotropic pathogens hepatitis C virus (HCV) and hepatitis B virus (HBV). Both strains of ORFV showed anti-viral activity against HCV in vitro and against HBV in a transgenic mouse model without signs of necro-inflammation in vivo. Our experiments suggest that the absence of liver damage is potentially mediated by iORFV-induced downregulation of antigen cross-presentation in liver sinus endothelial cells. Furthermore, both strains showed significant anti-fibrotic activity in rat models of liver fibrosis. iORFV strain NZ2 appeared more potent compared to strain D1701 with respect to both its antiviral and antifibrotic activity on the basis of dosages estimated by titration of active virus. These results show a potential therapeutic approach against two important human liver pathogens HBV and HCV that independently addresses concomitant liver fibrosis. Further studies are required to characterize the details of the mechanisms involved in this novel therapeutic principle.
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