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Testicular germ cell cancer (TGCC) is subdivided into several subtypes. While seminomatous germ cell tumors (SGCT) are characterized by an intensive infiltration of immune cells which constitute a pro-inflammatory tumor micromilieu (TME), immune cells in non-seminomatous germ cell tumors (NSGCT) are differently composed and less abundant. Previously, we have shown that the seminomatous cell line TCam-2 promotes T cell and monocyte activation in a coculture model, resulting in mutual interactions between both cell types. Here we set out to compare this feature of TCam-2 cells with the non-seminomatous cell line NTERA-2. Peripheral blood T cells or monocytes cocultured with NTERA-2 cells failed to secrete relevant amounts of pro-inflammatory cytokines, and significantly downregulated the expression of genes encoding activation markers and effector molecules. In contrast, immune cells cocultured with TCam-2 cells produced IL-2, IL-6 and TNFα, and strongly upregulated the expression of multiple pro-inflammatory genes. Furthermore, the expression of genes involved in proliferation, stemness and subtype specification remained unaltered in NTERA-2 cells during coculture with T cells or monocytes, indicating the absence of mutual interactions. Collectively, our findings uncover fundamental differences between SGCT and NSGCT in their capability to generate a pro-inflammatory TME, which possibly impacts the clinical features and prognosis of both TGCC subtypes.

Glucocorticoids (GCs) constitute one of the most powerful classes of anti-inflammatory agents and are used for the treatment of a plethora of diseases related to autoimmunity, allergy, cancer, and infection. In the last two decades, multiple studies using genetically engineered mice with targeted deletions of the GC receptor (GR) in individual cell types have provided insights into the mechanisms of GCs in the control of the immune system. The characterization of GR expression in these mouse models, however, mostly relied on the analysis of mRNA expression or reporter gene activity. In contrast, approaches directly detecting the GR protein on a cellular level are scarce. Thus, we here used a flow cytometric method to analyze mice in which the GR gene locus was disrupted with the help of a Cre recombinase expressed under the control of either the lck or the lysM promoter. Measuring GR protein expression in immune cell subpopulations unveiled an efficient and highly selective depletion in both strains of knock-out mice in accordance with the expected cellular specificity of the employed promoters for T cells or myeloid cells, respectively. The flow cytometric data were well in line with those from the analysis of GR mRNA expression in magnetically sorted immune cell subpopulations but they could be obtained much more quickly. In summary, our data indicate that flow cytometry is a powerful tool with which to define GR protein content at a single cell level when studying the function of GCs in the immune system.

Glucocorticoids (GCs) are widely used to treat acute graft‐versus‐host disease (aGvHD) due to their immunosuppressive activity, but they also reduce the beneficial graft‐versus‐leukemia (GvL) effect of the allogeneic T cells contained in the graft. Here, we tested whether aGvHD therapy could be improved by delivering GCs with the help of inorganic–organic hybrid nanoparticles (IOH‐NPs) that preferentially target myeloid cells. IOH‐NPs containing the GC betamethasone (BMP‐NPs) efficiently reduced morbidity, mortality, and tissue damage in a totally MHC mismatched mouse model of aGvHD. Therapeutic activity was lost in mice lacking the GC receptor (GR) in myeloid cells, confirming the cell type specificity of our approach. BMP‐NPs had no relevant systemic activity but suppressed cytokine and chemokine gene expression locally in the small intestine, which presumably explains their mode of action. Most importantly, BMP‐NPs delayed the development of an adoptively transferred B cell lymphoma better than the free drug, although the overall incidence was unaffected. Our findings thus suggest that employing IOH‐NPs could diminish the risk of relapse associated with GC therapy of aGvHD patients while still allowing to efficiently ameliorate the disease.

We previously reported that inorganic-organic hybrid nanoparticles (IOH-NPs) containing the synthetic glucocorticoid (GC) betamethasone show efficient anti-inflammatory activity in mice. Here, we employed IOH-NPs with the chemical composition Gd3+2[AMP]2−3 (AMP: adenosine monophosphate) to determine their in vivo distribution by magnetic resonance imaging after intraperitoneal injection. We show that IOH-NPs distribute throughout the peritoneal cavity from where they get rapidly cleared and then localize to abdominal organs. Our findings were confirmed by analyzing individual mouse organs ex vivo following injection of IOH-NPs with the chemical composition [ZrO]2+[(BMP)0.9(FMN)0.1]2− (BMP: betamethasone phosphate, FMN: flavin mononucleotide) or [ZrO]2+[(HPO4)0.9(FMN)0.1]2− using inductively coupled plasma mass spectrometry and flow cytometry. To characterize the mechanism of cellular uptake in vitro, we tested different cell lines for their ability to engulf IOH-NPs by flow cytometric analysis taking advantage of the incorporated fluorescent dye FMN. We found that IOH-NPs were efficiently taken up by macrophages, to a lesser extent by fibroblasts, epithelial cells, and myoblasts, and hardly at all by both T and B lymphocytes. Characterization of the endocytic pathway further suggested that IOH-NPs were internalized by macropinocytosis, and imaging flow cytometry revealed a strong colocalization of the engulfed IOH-NPs with the lysosomal compartment. Intracellular release of the functional anions from IOH-NPs was confirmed by the ability of the GC betamethasone to downregulate the expression of surface receptors on bone marrow-derived macrophages. Taken together, our findings unveil the mechanistic basis of an anti-inflammatory GC therapy with IOH-NPs, which may entail translational approaches in the future.

Testis is an immune privileged site, a feature that prevents germ cells from eliciting an autoimmune response. Macrophages contribute to this state of tolerance by adopting an immunoregulatory phenotype. Here, we further characterized their features in mice by analyzing surface markers, anatomic localization as well as morphology and function. Testicular macrophages (TMΦ) were stained for various surface receptors, and MHCII and CD206 were found to be most suitable to discriminate between two subpopulations. Our immunohistochemical analysis further confirmed a predominant localization of CD206

Background & Aims Inflammatory bowel disease is commonly treated by administration of glucocorticoids. While the importance of intestinal epithelial cells for the pathogenesis of this disorder is widely accepted, their role as target cells for glucocorticoids has not been explored. To address this issue, we induced colonic inflammation in GRvillin mice, which carry an inducible deletion of the glucocorticoid receptor in intestinal epithelial cells. Methods Colitis and colitis-associated colorectal cancer were induced by administration of dextran sulfate sodium and azoxymethane in mice. Clinical parameters, epithelial permeability and tumor development were monitored during disease progression. Colon tissue, lamina propria cells and intestinal epithelial cells were examined by gene expression analyses, flow cytometry, histopathology, and immunohistochemistry. Results The absence of the intestinal epithelial glucocorticoid receptor aggravated clinical symptoms and tissue damage, and compromised epithelial barrier integrity during colitis. Gene expression of chemokines, pattern recognition receptors and molecules controlling epithelial permeability was dysregulated in intestinal epithelial cells of GRvillin mice, leading to a reduced recruitment and a hyperactivation of leukocytes in the lamina propria of the colon. Importantly, the exaggerated inflammatory response in GRvillin mice also enhanced associated tumorigenesis, resulting in a higher number and larger size of tumors in the colon. Conclusions Our results reveal an important role of intestinal epithelial cells as targets of glucocorticoid action in inflammatory bowel disease and suggest that the efficacy with which colitis is kept at bay directly affects the progression of colorectal cancer., Graphical abstract

BACKGROUND AND OBJECTIVE Extracorporeal photopheresis (ECP) is an important immune tolerance inducing therapy for graft-versus-host disease (GvHD). However, a sufficient number of ECP cycles cannot be performed in patients with severe GvHD and contraindications for apheresis. Allogeneic sources of leucocytes for use as ECP treatment would be of great benefit. Therefore, this study aimed to test the therapeutic potential of novel sources of leucocytes for ECP. MATERIALS AND METHODS Graft-versus-host disease mice were treated with ECP using therapeutic cells from different allogeneic sources. Splenocytes were incubated with 8-methoxypsoralen (8-MOP), irradiated with UVA light and injected into GvHD mice as a model for ECP. RESULTS The therapy with 8-MOP/UVA-treated cells from healthy mice of the bone marrow transplantation (BMT) donor strain reduced the GvHD symptoms, at least in a model of chronic GvHD. In the acute GvHD model, 8-MOP/UVA-treated cells from the BMT donor or recipient strain did not show significant improvements in GvHD symptoms or survival time. Pre-activation of cells by mixed lymphocyte reactions before 8-MOP/UVA treatment also failed to result in significant differences in survival time or GvHD score. In contrast, ECP with third-party 8-MOP/UVA-treated cells from a HLA-mismatched donor resulted in a mean survival time of 37 days compared to 21 days in the control group. CONCLUSION In our analysis of novel allogeneic leucocyte sources for ECP, we could demonstrate that the source of the 8-MOP/UVA-treated cells is crucial. The underlying immunologic effect of allogeneic 8-MOP/UVA-treated cells needs to be investigated in future studies.

TNF is an important mediator in numerous inflammatory diseases, e.g., in inflammatory bowel diseases (IBDs). In IBD, acute increases in TNF production can lead to disease flares. Glucocorticoids (GCs), which are steroids that bind and activate the glucocorticoid receptor (GR), are able to protect animals and humans against acute TNF-induced inflammatory symptoms. Mice with a poor transcriptional response of GR dimer-dependent target genes were studied in a model of TNF-induced lethal inflammation. In contrast to the GRWT/WT mice, these GRdim/dim mice displayed a substantial increase in TNF sensitivity and a lack of protection by the GC dexamethasone (DEX). Unchallenged GRdim/dim mice had a strong IFN-stimulated gene (ISG) signature, along with STAT1 upregulation and phosphorylation. This ISG signature was gut specific and, based on our studies with antibiotics, depended on the gut microbiota. GR dimers directly bound to short DNA sequences in the STAT1 promoter known as inverted repeat negative GRE (IR-nGRE) elements. Poor control of STAT1 in GRdim/dim mice led to failure to repress ISG genes, resulting in excessive necroptosis induction by TNF. Our findings support a critical interplay among gut microbiota, IFNs, necroptosis, and GR in both the basal response to acute inflammatory challenges and pharmacological intervention by GCs.

Although glucocorticoids (GCs) are a mainstay in the clinical management of asthma, the target cells that mediate their therapeutic effects are unknown. Contrary to our expectation, we found that GC receptor (GR) expression in immune cells was dispensable for successful therapy of allergic airway inflammation (AAI) with dexamethasone. Instead, GC treatment was compromised in mice expressing a defective GR in the nonhematopoietic compartment or selectively lacking the GR in airway epithelial cells. Further, we found that an intact GR dimerization interface was a prerequisite for the suppression of AAI and airway hyperresponsiveness by GCs. Our observation that the ability of dexamethasone to modulate gene expression in airway epithelial cells coincided with its potency to resolve AAI supports a crucial role for transcriptional regulation by the GR in this cell type. Taken together, we identified an unknown mode of GC action in the treatment of allergic asthma that might help to develop more specific therapies in the future.

Graft-versus-host disease (GvHD) still belongs to the major challenges after allogeneic hematopoietic stem cell transplantation (HSCT). Immune-suppressive therapy against GvHD is a double-edged sword due to risk of infections and relapse. The ability to adapt prophylactic treatment according to the probability of severe GvHD would be an essential advantage for the patients. We analyzed different biomarkers for their potential to predict the development of GvHD in 28 patients who underwent allogeneic HSCT. Blood was taken once directly after hematopoietic engraftment. In this study, patients were monitored for 12 months after HSCT for the occurrence of acute GvHD or acute/chronic GvHD overlap syndrome. Soluble IL-2 receptor and CD4/CD8 T cell ratio were independently associated with the occurrence of GvHD in the observation period. However, the largest area under the receiver operating characteristic curve with 0.90 was observed when a 5-parameter biomarker score based on CD4+ T cells, CD8+ T cells, CD19− CD21+ precursor B cells, CD4/CD8 T cell ratio, and soluble IL-2 receptor was used to predict GvHD. In addition, CD8+ T cell levels above 2.3% of all mononuclear cells after engraftment may predict relapse-free survival at least for 12 months. In summary, we found a new biomarker panel for prediction of GvHD which is featured by established laboratory assays and high statistical significance. In order to introduce the biomarker panel into routine clinical protocols, we suggest performing a larger multi-center study.

Glucocorticoids (GC) are widely used to treat acute relapses in multiple sclerosis (MS) patients, but their application is accompanied by side effects due to their broad spectrum of action. Here, we report on the therapeutic option to apply GC via inorganic-organic hybrid nanoparticles (IOH-NP) with the composition [ZrO]2+[(BMP)0.9(FMN)0.1]2- (designated BMP-NP with BMP: betamethasone phosphate; FMN: flavinmononucleotide). We found that these BMP-NP have an increased cell type-specificity compared to free GC while retaining full therapeutic efficacy in a mouse model of MS. BMP-NP were preferentially taken up by phagocytic cells and modulated macrophages in vivo more efficiently than T cells. When GC were applied in the form of BMP-NP, treatment of neuroinflammatory disease in mice exclusively depended on the control of macrophage function whereas effects on T cells and brain endothelial cells were dispensable for therapeutic efficacy. Importantly, BMP-NP were not only active in mice but also showed strong activity towards monocytes isolated from healthy human volunteers. We conclude that application of GC via IOH-NP has the potential to improve MS therapy in the future.

Glucocorticoids (GCs) play an important role in controlling acute graft-versus-host disease (aGvHD), a frequent complication of allogeneic hematopoietic stem cell transplantation. The anti-inflammatory activity of GCs is mainly ascribed to the modulation of T cells and macrophages, for which reason a genetically induced GC resistance of either of these cell types causes aggravated aGvHD. Since only a few genes are currently known that are differentially regulated under these conditions, we analyzed the expression of 54 candidate genes in the inflamed small intestine of mice suffering from aGvHD when either allogeneic T cells or host myeloid cells were GC resistant using a microfluidic dynamic array platform for high-throughput quantitative PCR. The majority of genes categorized as cytokines (e.g. Il2, Il6), chemokines (e.g. Ccl2, Cxcl1), cell surface receptors (e.g. Fasl, Ctla4) and intracellular molecules (e.g. Dusp1, Arg1) were upregulated in mice transplanted with GC resistant allogeneic T cells. Moreover, the expression of several genes linked to energy metabolism (e.g. Glut1) was altered. Surprisingly, mice harboring GC resistant myeloid cells showed almost no changes in gene expression despite their fatal disease course after aGvHD induction. To identify additional genes in the inflamed small intestine that were affected by a GC resistance of allogeneic T cells, we performed an RNAseq analysis, which uncovered more than 500 differentially expressed transcripts (e.g. Cxcr6, Glut3, Otc, Aoc1, Il1r1, Sphk1) that were enriched for biological processes associated with inflammation and tissue disassembly. The changes in gene expression could be confirmed during full-blown disease but hardly any of them in the preclinical phase using high-throughput quantitative PCR. Further analysis of some of these genes revealed a highly selective expression pattern in T cells, intestinal epithelial cells and macrophages, which correlated with their regulation during disease progression. Collectively, we identified an altered gene expression profile caused by GC resistance of transplanted allogeneic T cells, which could help to define new targets for aGvHD therapy.

The limited efficacy of glucocorticoids (GCs) during therapy of acute relapses in multiple sclerosis (MS) leads to long-term disability. We investigated the potential of vitamin D (VD) to enhance GC efficacy and the mechanisms underlying this VD/GC interaction. In vitro, GC receptor (GR) expression levels were quantified by ELISA and induction of T cell apoptosis served as a functional readout to assess synergistic 1,25(OH)2D3 (1,25D)/GC effects. Experimental autoimmune encephalomyelitis (MOG35–55 EAE) was induced in mice with T cell-specific GR or mTORc1 deficiency. 25(OH)D (25D) levels were determined in two independent cohorts of MS patients with stable disease or relapses either responsive or resistant to GC treatment (initial cohort: n = 110; validation cohort: n = 85). Gene expression of human CD8+ T cells was analyzed by microarray (n = 112) and correlated with 25D serum levels. In vitro, 1,25D upregulated GR protein levels, leading to increased GC-induced T cell apoptosis. 1,25D/GC combination therapy ameliorated clinical EAE course more efficiently than respective monotherapies, which was dependent on GR expression in T cells. In MS patients from two independent cohorts, 25D deficiency was associated with GC-resistant relapses. Mechanistic studies revealed that synergistic 1,25D/GC effects on apoptosis induction were mediated by the mTOR but not JNK pathway. In line, 1,25D inhibited mTORc1 activity in murine T cells, and low 25D levels in humans were associated with a reduced expression of mTORc1 inhibiting tuberous sclerosis complex 1 in CD8+ T cells. GR upregulation by 1,25D and 1,25D/GC synergism in vitro and therapeutic efficacy in vivo were abolished in animals with a T cell-specific mTORc1 deficiency. Specific inhibition of mTORc1 by everolimus increased the efficacy of GC in EAE. 1,25D augments GC-mediated effects in vitro and in vivo in a T cell-specific, GR-dependent manner via mTORc1 inhibition. These data may have implications for improvement of anti-inflammatory GC therapy. Electronic supplementary material The online version of this article (10.1007/s00401-019-02018-8) contains supplementary material, which is available to authorized users.

T-cell lymphopenia is a major risk factor for autoimmunity. Here we describe congenic Lewis (LEW) rats with a loss-of-function mutation in the Gimap5 gene, leading to a 92% reduction in peripheral T-cell numbers. Gimap5-deficient LEW rats developed eosinophilic autoimmune gastroenteritis accompanied by a 40-fold increase in IgE serum levels. This phenotype was ameliorated by antibiotic treatment, indicating a critical role of the microbial flora in the development of inflammatory bowel disease. Interestingly, Gimap5-deficient LEW rats showed strongly aggravated experimental autoimmune encephalomyelitis (EAE) after immunization with guinea pig myelin basic protein. This phenotype, however, persisted after antibiosis, confirming that the enhanced CNS autoimmune response in T-cell lymphopenic Gimap5-deficient LEW rats was unrelated to the composition of the microbial flora. Rather, it seems that it was caused by the 7-fold increase in the percentage of activated T cells producing IL-17 and IFN-γ, and the skewed T-cell receptor (TCR) repertoire, both of which were the result of T-cell lymphopenia and not affected by antibiosis. This notion was supported by the observation that adoptive T-cell transfer corrected the TCR repertoire and improved EAE. Collectively, our findings confirm a critical albeit differential role of T-cell lymphopenia in the susceptibility to organ-specific autoimmune responses.-Fischer, H. J., Witte, A.-K., Walter, L., Gröne, H.-J., van den Brandt, J., Reichardt, H. M. Distinct roles of T-cell lymphopenia and the microbial flora for gastrointestinal and CNS autoimmunity.

MS is a highly prevalent neuroinflammatory disease of presumed autoimmune origin. Clinical observations and animal studies suggest that CD8(+) T cells play an important role in MS but their exact mechanisms are ill defined. When we actively induced EAE in CD8 knock-out DA rats, or adoptively transferred encephalitogenic CD4(+) T cells into CD8 knock-out DA rats, the disease course was indistinguishable from controls. Since our previous findings had revealed that the absence of CD8(+) T cells in Lewis rats ameliorated EAE, we compared antigen-induced T cell differentiation in both strains. Disease onset and the composition of the draining lymph nodes were similar but T cell activation in DA rats was much weaker. Moreover, oligoclonal expansion of CD8(+) T cells was exclusively observed in Lewis but not in DA rats. This suggests that myelin-specific CD8(+) T cells are involved in the differentiation of encephalitogenic CD4(+) T cells in Lewis rats, whilst they do not impact CD4(+) T cell priming in DA rats. Hence, clonal expansion of CD8(+) T cells in secondary lymphoid organs appears to be linked to their ability to modulate CNS autoimmune responses.

The grey matter is a central target of pathological processes in neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases. The grey matter is often also affected in multiple sclerosis, an autoimmune disease of the central nervous system. The mechanisms that underlie grey matter inflammation and degeneration in multiple sclerosis are not well understood. Here we show that, in Lewis rats, T cells directed against the neuronal protein β-synuclein specifically invade the grey matter and that this is accompanied by the presentation of multifaceted clinical disease. The expression pattern of β-synuclein induces the local activation of these T cells and, therefore, determined inflammatory priming of the tissue and targeted recruitment of immune cells. The resulting inflammation led to significant changes in the grey matter, which ranged from gliosis and neuronal destruction to brain atrophy. In humans, β-synuclein-specific T cells were enriched in patients with chronic-progressive multiple sclerosis. These findings reveal a previously unrecognized role of β-synuclein in provoking T-cell-mediated pathology of the central nervous system. In a rat model of multiple sclerosis, β-synuclein-specific T cells induce inflammation and pathological changes in the grey matter of the central nervous system; these cells were also found in higher numbers in patients with multiple sclerosis, particularly those with a chronic progressive course.

Inorganic‐organic hybrid nanoparticles (IOH‐NPs) with a general composition [ZrO]2+[RDyeOPO3]2−, [Ln]3+n/3[RDye(SO3)n]n−, [Ln(OH)]2+n/2[RDye(SO3)n]n−, or [LnO]+n[RDye(SO3)n]n− (Ln: lanthanide) are a novel class of nanomaterials for fluorescence detection and optical imaging. IOH‐NPs are characterized by an extremely high load of the fluorescent dye (70–85 wt‐%), high photochemical stability, straightforward aqueous synthesis, low material complexity, intense emission and high cell uptake at low toxicity. Besides full‐color emission, IOH‐NPs are suitable for multimodal imaging, singlet‐oxygen generation as well as drug delivery and drug release. This focus review presents the material concept of the IOH‐NPs as well as their synthesis and characterization. Their characteristic features are illustrated by selected in vitro and in vivo studies to initiate application in biology and medicine.

The putative protein tyrosine kinase (PTK) inhibitor tyrphostin AG126 has proven beneficial in various models of inflammatory disease. Yet molecular targets and cellular mechanisms remained enigmatic. We demonstrate here that AG126 treatment has beneficial effects in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. AG126 alleviates the clinical symptoms, diminishes encephalitogenic Th17 differentiation, reduces inflammatory CNS infiltration as well as microglia activation and attenuates myelin damage. We show that AG126 directly inhibits Bruton's tyrosine kinase (BTK), a PTK associated with B cell receptor and Toll-like receptor (TLR) signaling. However, BTK inhibition cannot account for the entire activity spectrum. Effects on TLR-induced proinflammatory cytokine expression in microglia involve AG126 hydrolysis and conversion of its dinitrile side chain to malononitrile (MN). Notably, while liberated MN can subsequently mediate critical AG126 features, full protection in EAE still requires delivery of intact AG126. Its anti-inflammatory potential and especially interference with TLR signaling thus rely on a dual mechanism encompassing BTK and a novel MN-sensitive target. Both principles bear great potential for the therapeutic management of disturbed innate and adaptive immune functions.

Glucocorticoids (GCs) are released from the adrenal gland during inflammation and help to keep immune responses at bay. Owing to their potent anti-inflammatory activity, GCs also play a key role in controlling acute graft-versus-host disease (aGvHD). Here we demonstrate that mice lacking the glucocorticoid receptor (GR) in T cells develop fulminant disease after allogeneic bone marrow transplantation. In a fully MHC-mismatched model, transfer of GR-deficient T cells resulted in severe aGvHD symptoms and strongly decreased survival times. Histopathological features were aggravated and infiltration of CD8(+) T cells into the jejunum was increased when the GR was not expressed. Furthermore, serum levels of IL-2, IFNγ, and IL-17 were elevated and the cytotoxicity of CD8(+) T cells was enhanced after transfer of GR-deficient T cells. Short-term treatment with dexamethasone reduced cytokine secretion but neither impacted disease severity nor the CTLs' cytolytic capacity. Importantly, in an aGvHD model in which disease development exclusively depends on the presence of CD8(+) T cells in the transplant, transfer of GR-deficient T cells aggravated clinical symptoms and reduced survival times as well. Taken together, our findings highlight that suppression of CD8(+) T-cell function is a crucial mechanism in the control of aGvHD by endogenous GCs.

Pregnancy is one of the strongest inducers of immunological tolerance. Disease activity of many autoimmune diseases including multiple sclerosis (MS) is temporarily suppressed by pregnancy, but little is known about the underlying molecular mechanisms. Here, we investigated the endocrine regulation of conventional and regulatory T cells (Tregs) during reproduction. In vitro, we found the pregnancy hormone progesterone to robustly increase Treg frequencies via promiscuous binding to the glucocorticoid receptor (GR) in T cells. In vivo, T-cell-specific GR deletion in pregnant animals undergoing experimental autoimmune encephalomyelitis (EAE), the animal model of MS, resulted in a reduced Treg increase and a selective loss of pregnancy-induced protection, whereas reproductive success was unaffected. Our data imply that steroid hormones can shift the immunological balance in favor of Tregs via differential engagement of the GR in T cells. This newly defined mechanism confers protection from autoimmunity during pregnancy and represents a potential target for future therapy.

Glucocorticoids (GCs) constitute a highly pleiotropic class of drugs predominantly employed in the treatment of inflammatory diseases. In our search for new mechanisms of action, we identified a hitherto unknown effect of GCs in the gastrointestinal tract. We found that oral administration of dexamethasone (Dex) to mice caused an enlargement of the stomach due to the induction of gastroparesis and that this effect was abolished in GRdim mice carrying the A458T mutation in the GC receptor (GR). Gastroparesis was unrelated to the enhanced gastric acid secretion observed after Dex treatment, although both effects were mediated by the same molecular mechanism of the GR. Using conditional GR-knockout mice, we could further rule out that GC effects on enterocytes or myeloid cells were involved in the induction of gastroparesis. In contrast, we found that Dex upregulated arginase 2 (Arg2) in the stomach both at the mRNA and protein level. This suggests that GC treatment leads to a depletion of l-arginine thereby impeding the production of nitric oxide (NO), which is required for gastric motility. We tested this hypothesis by supplementing the drinking water of the mice with exogenous l-arginine to compensate for the presumed shortage of this major substrate of NO synthases. Importantly, this measure completely prevented both the enlargement of the stomach and the induction of gastroparesis after Dex treatment. Our findings raise considerations of combining orally applied GCs with l-arginine to improve tolerability of GC treatment and provide a possible explanation for the antiemetic effects of GCs widely exploited in chemotherapy.

In this Article, owing to an error during the production process, the y-axis label of Fig. 2c should read "Number of Tβ-syn cells" rather than "Number of T1β-syn cells" and the left and right panels of Fig. 4 should be labelled 'a' and 'b', respectively. These errors have been corrected online.

PROBLEM: Steroid hormones such as progesterone and glucocorticoids rise during pregnancy and are accountable for the adaptation of the maternal immune system to pregnancy. How steroid hormones induce fetal tolerance is not fully understood. We hypothesized that steroid hormones selectively regulate the T cell response by promoting T cell death. METHOD OF STUDY: We incubated murine spleen cells isolated from non-pregnant and pregnant mice with physiological concentrations of steroid hormones in vitro and analyzed T cell subsets after 48 h of incubation. RESULTS: We found that progesterone and the synthetic glucocorticoid dexamethasone induce T cell death. CD4(+) regulatory T cells (T(reg)) were refractory towards progesterone-induced cell death, in contrast to conventional CD4(+) T cells, which resulted in a preferential enrichment of CD4(+) T(reg) cells in culture. T cells isolated from pregnant mice at early and late gestation showed comparable sensitivity to steroid-induced cell death. The target receptor for progesterone in immune cells is controversially discussed. We provide here support of progesterone binding to the glucocorticoid receptor as only T cells lacking the glucocorticoid but not the progesterone receptor showed resistance against progesterone-induced death. CONCLUSIONS: Our results indicate that high levels of progesterone during pregnancy can induce selective T cell death by binding the glucocorticoid receptor. Although physiological hormone concentrations were used, due to different bioavailability of steroid hormones in vivo these results have to be validated in an in vivo model. This mechanism might ensure immunological tolerance at the feto-maternal interface at gestation.

The role of CD8⁺ T cells in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) is still unclear. We describe here significantly reduced disease activity of EAE both in Lewis rats depleted of CD8⁺ T cells by monoclonal antibodies and CD8 knockout rats, which was accompanied by reduced leukocyte infiltration into the spinal cord. We detected myelin basic protein (MBP)-specific CD8⁺ T cells in peripheral lymphoid organs of CD8-depleted animals which, however, failed to differentiate into interferon-γ-producing effector cells. Our results indicate that CD8⁺ T cells interact with myelin-specific CD8⁺ T cells early in EAE enabling them to differentiate into pathogenic effector cells.

Multiple sclerosis is an autoimmune disease of the central nervous system (CNS) that is initiated when self-reactive T cells enter the brain and become locally activated after encountering their specific nervous antigens. When and where the disease-relevant antigen encounters occur is unclear. Here we combined fluorescently labeled nuclear factor of activated T cells (NFAT) with histone protein H2B to create a broadly applicable molecular sensor for intravital imaging of T cell activation. In experimental autoimmune encephalomyelitis, an animal model for multiple sclerosis, we report that effector T cells entering the CNS become activated after short contacts with leptomeningeal phagocytes. During established disease, the activation process is extended to the depth of the CNS parenchyma, where the cells form contacts with microglia and recruited phagocytes. We show that it is the activation processes during the preclinical phase rather than during established disease that are essential for the intensity and duration of the disease bout.

T cell activation is an energy-demanding process fueled by increased glucose consumption and accompanied by upregulation of the insulin receptor (INSR). In this article, we report that silencing the INSR in inducible knockdown rats impairs selective T cell functions but not thymocyte development. Glucose transport and glycolysis in activated CD4+ T cells were compromised in the absence of the INSR, which was associated with alterations in intracellular signaling pathways. The observed metabolic defects coincided with reduced cytokine production, proliferation, and migration, as well as increased apoptosis of CD4+ T cells. The cytotoxicity of CD8+ T cells in response to alloantigens was also diminished under these conditions, whereas the frequency and suppressive capacity of regulatory T cells were unaffected. The observed impairments proved to be decisive in vivo because silencing of the INSR attenuated clinical symptoms in animal models of acute graft-versus-host disease and multiple sclerosis. Taken together, our results suggest that upregulation of the INSR on T cells following activation is required for efficient adaptive immunity.

// L. Milena Beschel 1, * , Martin Leu 2, * , Sybille D. Reichardt 1 , Margret Rave-Frank 2 , Markus A. Schirmer 2, 3 , Christine Stadelmann 4 , Martin Canis 5 , Hendrik A. Wolff 6, 7 , Holger M. Reichardt 1, * 1 Institute for Cellular and Molecular Immunology, University Medical Center, Georg-August-University Gottingen, Germany 2 Department of Radiotherapy and Radiooncology, University Medical Center, Georg-August-University Gottingen, Germany 3 Institute of Clinical Pharmacology, University Medical Center, Georg-August-University Gottingen, Germany 4 Institute of Neuropathology, University Medical Center, Georg-August-University Gottingen, Germany 5 Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center, Georg-August-University Gottingen, Germany 6 University Medical Center, Georg-August-University Gottingen, Germany 7 Present address: Strahlentherapie Radiologie Munchen, Germany * These authors share first and senior authorships Correspondence to: Holger Reichardt, email: hreichardt@med.uni-goettingen.de Keywords: head and neck squamous cell carcinoma, acute organ toxicity, chemoradiotherapy, T cell, predictive marker Received: June 04, 2016 Accepted: August 15, 2016 Published: August 29, 2016 ABSTRACT Treatment of head and neck squamous cell carcinoma (HNSCC) by chemoradiotherapy (CRT) often results in high-grade acute organ toxicity (HGAOT). As these adverse effects impair the patients’ quality of life and the feasibility of the planned therapy, we sought to analyze immunological parameters in tumor material and blood samples obtained from 48 HNSCC patients in order to assess the potential to predict the individual acute organ toxicity. T cells in the tumor stroma were enriched in patients developing HGAOT whereas levels of soluble factors in the plasma and gene expression in whole blood did not coincide with the occurrence of acute organ toxicity. In contrast, the frequency and absolute numbers of selected leukocyte subpopulations measured in samples of peripheral blood mononuclear cells (PBMCs) directly before the beginning of CRT were significantly different in patients with HGAOT as compared to those without. When we validated several potential markers including the abundance of T cells in a small prospective study with 16 HNSCC patients, we were able to correctly predict acute organ toxicity in up to 81% of the patients. We conclude that analysis of PBMCs by fluorescence-activated cell sorting (FACS) might be a convenient strategy to identify patients at risk of developing HGAOT caused by CRT, which might allow to adapt the treatment regimen and possibly improve disease outcome.

Recent data suggest that donor-specific memory T cells (T(mem)) are an independent risk factor for rejection and poor graft function in patients and a major challenge for immunosuppression minimizing strategies. Many tolerance induction protocols successfully proven in small animal models e.g. costimulatory blockade, T cell depletion failed in patients. Consequently, there is a need for more predictive transplant models to evaluate novel promising strategies, such as adoptive transfer of regulatory T cells (Treg). We established a clinically more relevant, life-supporting rat kidney transplant model using a high responder (DA to LEW) recipients that received donor-specific CD4(+)/ 8(+) GFP(+) T(mem) before transplantation to achieve similar pre-transplant frequencies of donor-specific T(mem) as seen in many patients. T cell depletion alone induced long-term graft survival in naïve recipients but could not prevent acute rejection in T(mem)(+) rats, like in patients. Only if T cell depletion was combined with permanent CNI-treatment, the intragraft inflammation, and acute/chronic allograft rejection could be controlled long-term. Remarkably, combining 10 days CNI treatment and adoptive transfer of Tregs (day 3) but not Treg alone also induced long-term graft survival and an intragraft tolerance profile (e.g. high TOAG-1) in T(mem)(+) rats. Our model allows evaluation of novel therapies under clinically relevant conditions.

Apoptosis is synonymous to programmed cell death, which occurs in response to a plethora of stimuli and employs a series of highly conserved mediators and pathways. Its ambivalent role in immunology is illustrated by the fact that this process not only serves homeostatic functions but also exerts harmful effects including tissue damage. This is particularly true for neuroinflammatory diseases such as multiple sclerosis (MS), the most frequent neurological disease to afflict adolescents in the western world. Considerable insight into the role of apoptosis in MS has been obtained by using its animal model experimental autoimmune encephalomyelitis (EAE). Experiments using the EAE model have revealed that cell death affects both infiltrating lymphocytes and CNS resident cells, and that it contributes to axonal injury as well as the resolution of inflammation. Furthermore, it was discovered that the molecules involved in inducing and regulating this process are the Fas-FasL system, pro- and anti-apoptotic Bcl-2 family members, 'initiator' and 'effector' caspases, glucocorticoid hormones and various modulatory proteins. The variety of apoptotic mechanisms in combination with their often opposing effects on the disease course highlights the need for a detailed understanding of apoptosis in this context. In the future, this may pave the way to novel approaches aiming at interfering with the apoptotic process to prevent tissue damage or at intentionally inducing cell death in order to ameliorate the disease by deleting autoreactive lymphocytes.

Gene-targeting studies in mice have identified the essential roles of most prosurvival Bcl-2 family members in normal physiology and under conditions of stress. The function of one member, Bcl2a1/Bfl-1/A1, is only poorly understood because of quadruplication of its gene locus in mice, hindering conventional knockout studies. To overcome this problem, we generated mouse models allowing traceable constitutive or reversible ablation of A1 in the hematopoietic system by RNA interference. Knockdown of A1 impaired early stages of T-cell differentiation, B-cell homeostasis, and sensitized transitional as well as follicular B cells to apoptosis induced by ligation of the B-cell receptor. As a consequence, B-cell proliferation in response to mitogens was severely impaired, whereas that of T cells appeared unaffected. Furthermore, depending on the extent of A1 knockdown, granulocytes showed increased spontaneous death in culture or failed to accumulate in significant numbers in vivo. These models highlight the critical role of A1 in leukocyte development and homeostasis, constituting valuable tools for investigating presumed roles of this Bcl-2 family member in immunity, tumorigenesis, and drug resistance.

Glucocorticoids (GCs) are widely used to treat inflammatory diseases such as multiple sclerosis (MS). They predominantly act through the GC receptor, a member of the nuclear receptor superfamily that controls transcription by several different mechanisms. Owing to its ubiquitous expression, there are a variety of cell types that could serve as GC targets in the pathogenesis and treatment of MS. This brings about a great diversity of mechanisms potentially involved in the modulation of neuroinflammation by GCs, including the induction of apoptosis, repression of pro-inflammatory mediators and the expansion of myeloid-derived suppressor cells. Nevertheless, it is not well understood which of these mechanisms are essential for therapeutic efficacy. In this review, we summarise findings made concerning the actions of GCs in MS and its animal model experimental autoimmune encephalomyelitis, and also elucidate current concepts and developments that pertain to this clinically highly relevant treatment regimen.

The activity of acid sphingomyelinase (aSMase) was previously reported to be involved in glucocorticoid-induced cell death (GICD) of T lymphocytes. This mechanism in turn is believed to contribute to the therapeutic efficacy of glucocorticoids (GCs) in the treatment of inflammatory diseases. In this study, we reassessed the role of aSMase in GICD by using aSMase knockout mice. The absence of aSMase largely abolished the partial protection that effector memory CD4+ T cells in wild-type mice possess against GICD. Reduced IL-2 secretion by aSMase-deficient CD4+ T cells suggested that a lack of this important survival factor might be the cause of these cells’ enhanced susceptibility to GICD. Indeed, addition of IL-2 restored the protection against GICD, whereas neutralization of IL-2 abrogated the otherwise protective effect seen in wild-type effector memory CD4+ T cells. The therapeutic implications of the altered sensitivity of aSMase-deficient T cells to GICD were assessed in models of inflammatory disorders; namely, experimental autoimmune encephalomyelitis and acute graft-versus-host disease. Surprisingly, GC treatment was equally efficient in both models in terms of ameliorating the diseases, regardless of the genotype of the T cells. Thus, our data reveal a hitherto unrecognized contribution of aSMase to the sensitivity of effector memory CD4+ T cells to GICD and call into question the traditionally attributed importance of GICD of T cells to the treatment of inflammatory diseases by GCs.

SummaryDevelopment of osteoporosis severely complicates long-term glucocorticoid (GC) therapy. Using a Cre-transgenic mouse line, we now demonstrate that GCs are unable to repress bone formation in the absence of glucocorticoid receptor (GR) expression in osteoblasts as they become refractory to hormone-induced apoptosis, inhibition of proliferation, and differentiation. In contrast, GC treatment still reduces bone formation in mice carrying a mutation that only disrupts GR dimerization, resulting in bone loss in vivo, enhanced apoptosis, and suppressed differentiation in vitro. The inhibitory GC effects on osteoblasts can be explained by a mechanism involving suppression of cytokines, such as interleukin 11, via interaction of the monomeric GR with AP-1, but not NF-κB. Thus, GCs inhibit cytokines independent of GR dimerization and thereby attenuate osteoblast differentiation, which accounts, in part, for bone loss during GC therapy.