The contribution of microglia to ischemic cortical stroke is of particular therapeutic interest because of the impact on the survival of brain tissue in the ischemic penumbra, a region that is potentially salvable upon a brain infarct. Whether or not tissue in the penumbra survives critically depends on blood flow and vessel perfusion. To study the role of microglia in cortical stroke and blood vessel stability, CX3CR1(+/GFP) mice were subjected to transient middle cerebral artery occlusion and then microglia were investigated using time-lapse two-photon microscopy in vivo. Soon after reperfusion, microglia became activated in the stroke penumbra and started to expand cellular protrusions towards adjacent blood vessels. All microglia in the penumbra were found associated with blood vessels within 24 h post reperfusion and partially fully engulfed them. In the same time frame blood vessels became permissive for blood serum components. Migration assays in vitro showed that blood serum proteins leaking into the tissue provided molecular cues leading to the recruitment of microglia to blood vessels and to their activation. Subsequently, these perivascular microglia started to eat up endothelial cells by phagocytosis, which caused an activation of the local endothelium and contributed to the disintegration of blood vessels with an eventual break down of the blood brain barrier. Loss-of-microglia-function studies using CX3CR1(GFP/GFP) mice displayed a decrease in stroke size and a reduction in the extravasation of contrast agent into the brain penumbra as measured by MRI. Potentially, medication directed at inhibiting microglia activation within the first day after stroke could stabilize blood vessels in the penumbra, increase blood flow, and serve as a valuable treatment for patients suffering from ischemic stroke.

Laquinimod is an orally administered compound that is under investigation in relapsing-remitting multiple sclerosis. To understand the mechanism by which laquinimod exerts its clinical effects, we have performed human and murine studies assessing its immunomodulatory properties. In experimental autoimmune encephalomyelitis, the therapeutic administration of laquinimod beginning during the recovery of SJL mice, prevented further relapses as expected and strongly reduced infiltration of CD4+ and CD8+ T cells in the central nervous system. We hypothesized that this beneficial effect was mediated by dendritic cells, since we and others found a modulation of different dendritic cell subsets under treatment. According to the findings on antigen-presenting cells in the murine system, we found a reduced capacity of human monocyte-derived dendritic cells treated with therapeutic concentrations of laquinimod, upon maturation with lipopolysaccharide, to induce CD4+ T cell proliferation and secretion of pro-inflammatory cytokines. Furthermore, laquinimod treatment of mature dendritic cells resulted in a decreased chemokine production by both murine and human dendritic cells, associated with a decreased monocyte chemo-attraction. In laquinimod-treated patients with multiple sclerosis we consistently found reduced chemokine and cytokine secretion by conventional CD1c+ dendritic cells upon lipopolysaccharide stimulation. Similarly to the animal model of relapsing-remitting multiple sclerosis, dendritic cell subsets were altered in patients upon laquinimod treatment, as the number of conventional CD1c+ and plasmacytoid CD303+ dendritic cells were decreased within peripheral blood mononuclear cells. Moreover, laquinimod treatment in patients with multiple sclerosis and mice modified the maturation of dendritic cells demonstrated by an upregulation of CD86 expression in vivo. Our data suggest that inhibition of the NF-κB pathway is responsible for the changes observed in dendritic cell maturation and functions. These findings indicate that laquinimod exhibits its disease-modulating activity in multiple sclerosis by downregulating immunogenicity of dendritic cell responses. We suggest that monitoring dendritic cell properties in multiple sclerosis should be implemented in future therapeutic trials.

Diminishing potential to replace damaged tissues is a hallmark for ageing of somatic stem cells, but the mechanisms remain elusive. Here, we present proteome-wide atlases of age-associated alterations in human haematopoietic stem and progenitor cells (HPCs) and five other cell populations that constitute the bone marrow niche. For each, the abundance of a large fraction of the ~12,000 proteins identified is assessed in 59 human subjects from different ages. As the HPCs become older, pathways in central carbon metabolism exhibit features reminiscent of the Warburg effect, where glycolytic intermediates are rerouted towards anabolism. Simultaneously, altered abundance of early regulators of HPC differentiation reveals a reduced functionality and a bias towards myeloid differentiation. Ageing causes alterations in the bone marrow niche too, and diminishes the functionality of the pathways involved in HPC homing. The data represent a valuable resource for further analyses, and for validation of knowledge gained from animal models.

Nodavirus has become a serious pathogen for a wide range of cultured marine fish species. In the present work, the expression of genes related to immune and inflammatory responses of sea bream (Sparus aurata L.), considered as non susceptible species, was studied both in vitro and in vivo. No replication of the virus was observed in head kidney macrophages and blood leukocytes. Moreover, the enhancement of expression of several immune genes (tumor necrosis factor alpha (TNFalpha), interleukin-1-beta (IL-1beta), interferon-induced Mx protein) was not detected in both head kidney macrophages and blood leucocytes in response to an in vitro infection with nodavirus. However, in vivo, nodavirus was detected 1 day post-infection (p.i.) by a reverse transcription-polymerase chain reaction (RT-PCR) in blood, liver, head kidney and brain of experimentally infected sea bream, while its presence clearly decreased in blood after 3 days p.i. Also, a transitory increment of the expression of TNFalpha and IL-1beta was detected in the brain of intramuscular (i.m.) infected sea bream 3 days p.i. In head kidney, the over expression of TNFalpha was only observed 1 day p.i. The expression of Mx, an interferon induced gene, was increased in brain and head kidney of infected sea bream, reaching values of 1300-fold compared to controls in brain three days post-infection. For comparative purposes, we analyzed the expression of the same genes on a susceptible species, such as sea bass (Dicentrarchus labrax) and, although the same pattern of expression was observed both in brain and kidney, the magnitude was different mainly in the case of brain, the key organ of the infection, where higher expression of TNFalpha and lower expression of Mx compared with control was observed.

In this paper, we describe sequences of fibrinogen-related proteins (FREPs) in the Mediterranean mussel Mytilus galloprovincialis (MuFREPs) with the fibrinogen domain probably involved in the antigen recognition, but without the additional collagen-like domain of ficolins, molecules responsible for complement activation by the lectin pathway. Although they do not seem to be true or primive ficolins since the phylogenetic analysis are not conclusive enough, their expression is increased after bacterial infection or PAMPs treatment and they present opsonic activities similar to mammalian ficolins. The most remarkable aspect of these sequences was the existence of a very diverse set of FREP sequences among and within individuals (different mussels do not share any identical sequence) which parallels the extraordinary complexity of the immune system, suggesting the existence of a primitive system with a potential capacity to recognize and eliminate different kind of pathogens.

In patients with acute myeloid leukemia and low percentages of aldehyde-dehydrogenase-positive cells, non-leukemic hematopoietic stem cells can be separated from leukemic cells. By relating hematopoietic stem cell frequencies to outcome we detected poor overall- and disease-free survival of patients with low hematopoietic stem cell frequencies. Serial analysis of matched diagnostic and follow-up samples further demonstrated that hematopoietic stem cells increased after chemotherapy in patients who achieved durable remissions. However, in patients who eventually relapsed, hematopoietic stem cell numbers decreased dramatically at the time of molecular relapse demonstrating that hematopoietic stem cell levels represent an indirect marker of minimal residual disease, which heralds leukemic relapse. Upon transplantation in immune-deficient mice cases with low percentages of hematopoietic stem cells of our cohort gave rise to leukemic or no engraftment, whereas cases with normal hematopoietic stem cell levels mostly resulted in multi-lineage engraftment. Based on our experimental data, we propose that leukemic stem cells have increased niche affinity in cases with low percentages of hematopoietic stem cells. To validate this hypothesis, we developed new mathematical models describing the dynamics of healthy and leukemic cells under different regulatory scenarios. These models suggest that the mechanism leading to decreases in hematopoietic stem cell frequencies before leukemic relapse must be based on expansion of leukemic stem cells with high niche affinity and the ability to dislodge hematopoietic stem cells. Thus, our data suggest that decreasing numbers of hematopoietic stem cells indicate leukemic stem cell persistence and the emergence of leukemic relapse.

Multiple sclerosis is a chronic autoimmune demyelinating disease of the central nervous system, which is thought to be triggered by environmental factors in genetically susceptible individuals leading to activation of autoreactive T lymphocytes. Large multi-centre genome-wide association studies have identified multiple genetic risk loci in multiple sclerosis. In this study, we investigated T cell transcriptomic changes in experimental autoimmune encephalomyelitis, an animal model for multiple sclerosis. We correlated these findings with the multiple sclerosis risk genes postulated by the most recent Immunochip analysis and found that multiple sclerosis susceptibility genes were significantly regulated in experimental autoimmune encephalomyelitis. Our data indicate that nine distinct genes associated with multiple sclerosis risk, Bach2, Il2ra, Irf8, Mertk, Odf3b, Plek, Rgs1, Slc30a7 and Thada, can be confirmed to be differentially regulated in pathogenic CD4(+) T cells. During the effector phase within the inflamed CNS, CD4(+) T cells undergo comprehensive transformation and we identified key transcription factors and signalling networks involved in this process. The transformation was linked to metabolic changes with the involvement of liver X receptor/retinoid X receptor signalling and cholesterol biosynthesis, which might control the T cell effector function in the central nervous system. Thus, our study confirms the involvement of multiple sclerosis risk genes in the pathophysiology of the animal model and sheds light on additional disease-relevant inflammatory networks.

Background: The European seabass (Dicentrarchus labrax), one of the most extensively cultured species in European aquaculture productions, is, along with the gilthead sea bream (Sparus aurata), a prospective model species for the Perciformes which includes several other commercially important species. Massive mortalities may be caused by bacterial or viral infections in intensive aquaculture production. Revealing transcripts involved in immune response and studying their relative expression enhances the understanding of the immune response mechanism and consequently also the creation of vaccines. The analysis of expressed sequence tags (EST) is an efficient and easy approach for gene discovery, comparative genomics and for examining gene expression in specific tissues in a qualitative and quantitative way.