Critical requirement of CD11b (Mac-1) on T cells and accessory cells for development of experimental autoimmune encephalomyelitis

The role of integrins in brain health and neurodegenerative diseases

Integrins are heterodimeric membrane proteins expressed on the surface of most cells. They mediate adhesion and signaling processes relevant for a wealth of physiological processes, including nervous system development and function. Interestingly, integrins are also recognized therapeutic targets for inflammatory diseases, such as multiple sclerosis. Here, we discuss the role of integrins in brain development and function, as well as in neurodegenerative diseases affecting the brain (Alzheimer's disease, multiple sclerosis, stroke). Furthermore, we discuss therapeutic targeting of these adhesion receptors in inflammatory diseases of the brain.

CD4+ CD11b+ T cells infiltrate and aggravate the traumatic brain injury depending on brain-to-cervical lymph node signaling

AIM

We aim to identify the specific CD4+ T-cell subtype influenced by brain-to-CLN signaling and explore their role during the acute phase of traumatic brain injury (TBI).

METHOD

Cervical lymphadenectomy or cervical afferent lymphatic ligation was performed before TBI. Cytokine array and western blot were used to detect cytokines, while the motor function was assessed using mNss and rotarod test. CD4+ T-cell subtypes in blood, brain, and CLNs were analyzed with Cytometry by time-of-flight analysis (CyTOF) or fluorescence-activated cell sorting (FACS). Brain edema and volume changes were measured by 9.4T MRI. Neuronal apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining.

RESULTS

Cervical lymphadenectomy and ligation of cervical lymphatic vessels resulted in a decreased infiltration of CD4+ T cells, specifically CD11b-positive CD4+ T cells, within the affected region. The population of CD4+ CD11b+ T cells increased in ligated CLNs, accompanied by a decrease in the average fluorescence intensity of sphingosine-1-phosphate receptor-1 (S1PR1) on these cells. Administration of CD4+ CD11b+ T cells sorted from CLNs into the lateral ventricle reversed the attenuated neurologic deficits, brain edema, and lesion volume following cervical lymphadenectomy.

CONCLUSION

The infiltration of CD4+ CD11b+ T cells exacerbates secondary brain damage in TBI, and this process is modulated by brain-to-CLN signaling.

Vivaria housing conditions expose sex differences in brain oxidation, microglial activation, and immune system states in aged hAPOE4 mice

Apolipoprotein E ε4 allele (APOE4) is the predominant genetic risk factor for late-onset Alzheimer's disease (AD). APOE4 mouse models have provided advances in the understanding of disease pathogenesis, but unaccounted variables like rodent housing status may hinder translational outcomes. Non-sterile aspects like food and bedding can be major sources of changes in rodent microflora. Alterations in intestinal microbial ecology can cause mucosal barrier impairment and increase pro-inflammatory signals. The present study examined the role of sterile and non-sterile food and housing on redox indicators and the immune status of humanized-APOE4 knock-in mice (hAPOe4). hAPOE4 mice were housed under sterile conditions until 22 months of age, followed by the transfer of a cohort of mice to non-sterile housing for 2 months. At 24 months of age, the redox/immunologic status was evaluated by flow cytometry/ELISA. hAPOE4 females housed under non-sterile conditions exhibited: (1) higher neuronal and microglial oxygen radical production and (2) lower CD68+ microglia (brain) and CD8+ T cells (periphery) compared to sterile-housed mice. In contrast, hAPOE4 males in non-sterile housing exhibited: (1) higher MHCII+ microglia and CD11b+CD4+ T cells (brain) and (2) higher CD11b+CD4+ T cells and levels of lipopolysaccharide-binding protein and inflammatory cytokines in the periphery relative to sterile-housed mice. This study demonstrated that sterile vs. non-sterile housing conditions are associated with the activation of redox and immune responses in the brain and periphery in a sex-dependent manner. Therefore, housing status may contribute to variable outcomes in both the brain and periphery.

Integrins in Health and Disease-Suitable Targets for Treatment?

Integrin receptors are heterodimeric surface receptors that play multiple roles regarding cell-cell communication, signaling, and migration. The four members of the β2 integrin subfamily are composed of an alternative α (CD11a-d) subunit, which determines the specific receptor properties, and a constant β (CD18) subunit. This review aims to present insight into the multiple immunological roles of integrin receptors, with a focus on β2 integrins that are specifically expressed by leukocytes. The pathophysiological role of β2 integrins is confirmed by the drastic phenotype of patients suffering from leukocyte adhesion deficiencies, most often resulting in severe recurrent infections and, at the same time, a predisposition for autoimmune diseases. So far, studies on the role of β2 integrins in vivo employed mice with a constitutive knockout of all β2 integrins or either family member, respectively, which complicated the differentiation between the direct and indirect effects of β2 integrin deficiency for distinct cell types. The recent generation and characterization of transgenic mice with a cell-type-specific knockdown of β2 integrins by our group has enabled the dissection of cell-specific roles of β2 integrins. Further, integrin receptors have been recognized as target receptors for the treatment of inflammatory diseases as well as tumor therapy. However, whereas both agonistic and antagonistic agents yielded beneficial effects in animal models, the success of clinical trials was limited in most cases and was associated with unwanted side effects. This unfavorable outcome is most probably related to the systemic effects of the used compounds on all leukocytes, thereby emphasizing the need to develop formulations that target distinct types of leukocytes to modulate β2 integrin activity for therapeutic applications.

Retinal transcriptome profiling identifies novel candidate genes associated with visual impairment in a mouse model of multiple sclerosis

Visual impairment is occasionally observed in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Although uveitis and optic neuritis have been reported in MS and EAE, the precise mechanisms underlying the pathogenesis of these visual impairments remain poorly understood. This study aims to identify differentially expressed genes (DEGs) in the retinas of mice with EAE to identify genes that may be implicated in EAE-induced visual impairment. Fourteen adult mice were injected with myelin oligodendrocyte glycoprotein35-55 to induce the EAE model. Transcriptomes of retinas with EAE were analyzed by RNA-sequencing. Gene expression analysis revealed 347 DEGs in the retinas of mice with EAE: 345 were upregulated, and 2 were downregulated (adjusted p-value < 0.05 and absolute log2 fold change > 1). Gene ontology (GO) analysis showed that the upregulated genes in the retinas of mice with EAE were primarily related to immune responses, responses to external biotic stimuli, defense responses, and leukocyte-mediated immunity in the GO biological process. The expression of six upregulated hub genes (c1qb, ctss, itgam, itgb2, syk, and tyrobp) from the STRING analysis and the two significantly downregulated DEGs (hapln1 and ndst4) were validated by reverse transcription-quantitative polymerase chain reaction. In addition, gene set enrichment analysis showed that the negatively enriched gene sets in EAE-affected retinas were associated with the neuronal system and phototransduction cascade. This study provides novel molecular evidence for visual impairments in EAE and indicates directions for further research to elucidate the mechanisms of these visual impairments in MS.

MicroRNA‑155 modulation of CD8+ T‑cell activity personalizes response to disease‑modifying therapies of patients with relapsing‑remitting multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease where activated immune cells can attack oligodendrocytes causing damage to the myelin sheath. Several molecular mechanisms are responsible for the auto-activation of immune cells such as RNA interference (RNAi) through microRNAs (miRNAs or miRs). In the present study, the role of miR-155 in regulating CD8⁺ T-cell activity in patients with relapsing-remitting multiple sclerosis (RRMS) was investigated, in terms of its migratory functions with regard to intracellular adhesion molecule-1 (ICAM1) and integrin subunit β2 (ITGB2), and its cytotoxic proteins, perforin and granzyme B. Gene expression of miR-155, ICAM1, ITGB2, perforin and granzyme B was evaluated following epigenetic modulations using reverse transcription-quantitative polymerase chain reaction in CD8⁺ T-cells isolated from blood samples of patients with RRMS and compared to healthy controls. The ectopic expression of miR-155 resulted in a persistent downregulation in all genes of interest related to CD8⁺ T-cell activation that were positively correlated with the Expanded Disability Status Scale of patients. The present study revealed the interplay between miR-155, ICAM1, and ITGB2, shedding light on their beneficial use as possible therapeutic regulators and diagnostic biomarkers of disease. Moreover, epigenetic modulations enhancing the efficacy of disease-modifying therapies (DMTs) may be employed as personalized therapy, to decrease the side effects of DMTs and improve the outcomes of patients.

Soluble ITGaM and ITGb2 Integrin Subunits Are Involved in Long-Term Pulmonary Complications after COVID-19 Infection

(1) Introduction: The role of soluble integrins in post-COVID-19 complications is unclear, especially in long-term pulmonary lesions. The purpose of this study was to investigate the association between soluble ITGa2, ITGaM and ITGb2 integrin subunits and long COVID-19 pulmonary complications. (2) Methodology: Post-COVID-19 patients were enrolled. According to the evidence of persistent interstitial lung lesions on CT, patients were divided into a long-term pulmonary complications group (P(+)) and a control group without long-term pulmonary complications (P(-)). We randomly selected 80 patients for further investigation (40 subjects for each group). Levels of ITGa2, ITGaM and ITGb2 integrin subunits were determined by ELISA assay. (3) Results: The serum concentration of sITGaM and sITGb2 were significantly higher in the P(+) group (sITGaM 18.63 ng/mL [IQR 14.17-28.83] vs. 14.75 ng/mL [IQR 10.91-20] p = 0.01 and sITGb2 10.55 ng/mL [IQR 6.53-15.83] vs. 6.34 ng/mL [IQR 4.98-9.68] p = 0.002). We observed a statistically significant correlation between sITGaM and sITGb2 elevation in the P(+) group (R = 0.42; p = 0.01). Patients from the P(+) group had a lower (1.82 +/-0.84 G/L) lymphocyte level than the P(-)group (2.28 +/-0.79 G/L), p = 0.03. Furthermore, we observed an inverse correlation in the P(-) group between blood lymphocyte count and sITGb2 integrin subunit levels (R = -0.49 p = 0.01). (4) Conclusions: Elevated concentrations of sITGaM and sITGb2 were associated with long-term pulmonary complications in post-COVID-19 patients. Both sITGaM and sITGb2 may be promising biomarkers for predicting pulmonary complications and could be a potential target for therapeutic intervention in post-COVID-19 patients.

β2 Integrins on Dendritic Cells Modulate Cytokine Signaling and Inflammation-Associated Gene Expression, and Are Required for Induction of Autoimmune Encephalomyelitis

Heterodimeric β2 integrin surface receptors (CD11a-d/CD18) are specifically expressed by leukocytes that contribute to pathogen uptake, cell migration, immunological synapse formation and cell signaling. In humans, the loss of CD18 expression results in leukocyte adhesion deficiency syndrome (LAD-)1, largely characterized by recurrent severe infections. All available mouse models display the constitutive and ubiquitous knockout of either α or the common β2 (CD18) subunit, which hampers the analysis of the cell type-specific role of β2 integrins in vivo. To overcome this limitation, we generated a CD18 gene floxed mouse strain. Offspring generated from crossing with CD11c-Cre mice displayed the efficient knockdown of β2 integrins, specifically in dendritic cells (DCs). Stimulated β2-integrin-deficient splenic DCs showed enhanced cytokine production and the concomitantly elevated activity of signal transducers and activators of transcription (STAT) 1, 3 and 5, as well as the impaired expression of suppressor of cytokine signaling (SOCS) 2–6 as assessed in bone marrow-derived (BM) DCs. Paradoxically, these BMDCs also showed the attenuated expression of genes involved in inflammatory signaling. In line, in experimental autoimmune encephalomyelitis mice with a conditional DC-specific β2 integrin knockdown presented with a delayed onset and milder course of disease, associated with lower frequencies of T helper cell populations (Th)1/Th17 in the inflamed spinal cord. Altogether, our mouse model may prove to be a valuable tool to study the leukocyte-specific functions of β2 integrins in vivo.

CEST MRI and MALDI imaging reveal metabolic alterations in the cervical lymph nodes of EAE mice

Background

Multiple sclerosis (MS) is a neurodegenerative disease, wherein aberrant immune cells target myelin-ensheathed nerves. Conventional magnetic resonance imaging (MRI) can be performed to monitor damage to the central nervous system that results from previous inflammation; however, these imaging biomarkers are not necessarily indicative of active, progressive stages of the disease. The immune cells responsible for MS are first activated and sensitized to myelin in lymph nodes (LNs). Here, we present a new strategy for monitoring active disease activity in MS, chemical exchange saturation transfer (CEST) MRI of LNs.

Methods and results

We studied the potential utility of conventional (T2-weighted) and CEST MRI to monitor changes in these LNs during disease progression in an experimental autoimmune encephalomyelitis (EAE) model. We found CEST signal changes corresponded temporally with disease activity. CEST signals at the 3.2 ppm frequency during the active stage of EAE correlated significantly with the cellular (flow cytometry) and metabolic (mass spectrometry imaging) composition of the LNs, as well as immune cell infiltration into brain and spinal cord tissue. Correlating primary metabolites as identified by matrix-assisted laser desorption/ionization (MALDI) imaging included alanine, lactate, leucine, malate, and phenylalanine.

Conclusions

Taken together, we demonstrate the utility of CEST MRI signal changes in superficial cervical LNs as a complementary imaging biomarker for monitoring disease activity in MS. CEST MRI biomarkers corresponded to disease activity, correlated with immune activation (surface markers, antigen-stimulated proliferation), and correlated with LN metabolite levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02493-z.

The Promiscuous Profile of Complement Receptor 3 in Ligand Binding, Immune Modulation, and Pathophysiology

The β2-integrin receptor family has a broad spectrum of physiological functions ranging from leukocyte adhesion, cell migration, activation, and communication to the phagocytic uptake of cells and particles. Among the members of this family, complement receptor 3 (CR3; CD11b/CD18, Mac-1, αMβ2) is particularly promiscuous in its functional profile and ligand selectivity. There are close to 100 reported structurally unrelated ligands for CR3, and while many ligands appear to cluster at the αMI domain, molecular details about binding modes remain largely elusive. The versatility of CR3 is reflected in its functional portfolio, which includes prominent roles in the removal of invaders and cell debris, induction of tolerance and synaptic pruning, and involvement in the pathogenesis of numerous autoimmune and chronic inflammatory pathologies. While CR3 is an interesting therapeutic target for immune modulation due to these known pathophysiological associations, drug development efforts are limited by concerns of potential interference with host defense functions and, most importantly, an insufficient molecular understanding of the interplay between ligand binding and functional impact. Here, we provide a systematic summary of the various interaction partners of CR3 with a focus on binding mechanisms and functional implications. We also discuss the roles of CR3 as an immune receptor in health and disease, as an activation marker in research and diagnostics, and as a therapeutic target.

Complement-dependent synapse loss and microgliosis in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory, neurodegenerative disease of the CNS characterized by both grey and white matter injury. Microglial activation and a reduction in synaptic density are key features of grey matter pathology that can be modeled with MOG_35-55 experimental autoimmune encephalomyelitis (EAE). Complement deposition combined with microglial engulfment has been shown during normal development and in disease as a mechanism for pruning synapses. We tested whether there is excess complement production in the EAE hippocampus and whether complement-dependent synapse loss is a source of degeneration in EAE using C1qa and C3 knockout mice. We found that C1q and C3 protein and mRNA levels were elevated in EAE mice. Genetic loss of C3 protected mice from EAE-induced synapse loss, reduced microglial activation, decreased the severity of the EAE clinical score, and protected memory/freezing behavior after contextual fear conditioning. C1qa KO mice with EAE showed little to no change on these measurements compared to WT EAE mice. Thus, pathologic expression and activation of the early complement pathway, specifically at the level of C3, contributes to hippocampal grey matter pathology in the EAE.

Complement: Bridging the innate and adaptive immune systems in sterile inflammation

The complement system is a collection of soluble and membrane-bound proteins that together act as a powerful amplifier of the innate and adaptive immune systems. Although its role in infection is well established, complement is becoming increasingly recognized as a key contributor to sterile inflammation, a chronic inflammatory process often associated with noncommunicable diseases. In this context, damaged tissues release danger signals and trigger complement, which acts on a range of leukocytes to augment and bridge the innate and adaptive immune systems. Given the detrimental effect of chronic inflammation, the complement system is therefore well placed as an anti-inflammatory drug target. In this review, we provide a general outline of the sterile activators, effectors, and targets of the complement system and a series of examples (i.e., hypertension, cancer, allograft transplant rejection, and neuroinflammation) that highlight complement's ability to bridge the 2 arms of the immune system.

β2 Integrins-Multi-Functional Leukocyte Receptors in Health and Disease

β2 integrins are heterodimeric surface receptors composed of a variable α (CD11a-CD11d) and a constant β (CD18) subunit and are specifically expressed by leukocytes. The α subunit defines the individual functional properties of the corresponding β2 integrin, but all β2 integrins show functional overlap. They mediate adhesion to other cells and to components of the extracellular matrix (ECM), orchestrate uptake of extracellular material like complement-opsonized pathogens, control cytoskeletal organization, and modulate cell signaling. This review aims to delineate the tremendous role of β2 integrins for immune functions as exemplified by the phenotype of LAD-I (leukocyte adhesion deficiency 1) patients that suffer from strong recurrent infections. These immune defects have been largely attributed to impaired migratory and phagocytic properties of polymorphonuclear granulocytes. The molecular base for this inherited disease is a functional impairment of β2 integrins due to mutations within the CD18 gene. LAD-I patients are also predisposed for autoimmune diseases. In agreement, polymorphisms within the CD11b gene have been associated with autoimmunity. Consequently, β2 integrins have received growing interest as targets in the treatment of autoimmune diseases. Moreover, β2 integrin activity on leukocytes has been implicated in tumor development.

Targeted Complement Inhibition at Synapses Prevents Microglial Synaptic Engulfment and Synapse Loss in Demyelinating Disease

Multiple sclerosis (MS) is a demyelinating, autoimmune disease of the central nervous system. While work has focused on myelin and axon loss in MS, less is known about mechanisms underlying synaptic changes. Using postmortem human MS tissue, a preclinical nonhuman primate model of MS, and two rodent models of demyelinating disease, we investigated synapse changes in the visual system. Similar to other neurodegenerative diseases, microglial synaptic engulfment and profound synapse loss were observed. In mice, synapse loss occurred independently of local demyelination and neuronal degeneration but coincided with gliosis and increased complement component C3, but not C1q, at synapses. Viral overexpression of the complement inhibitor Crry at C3-bound synapses decreased microglial engulfment of synapses and protected visual function. These results indicate that microglia eliminate synapses through the alternative complement cascade in demyelinating disease and identify a strategy to prevent synapse loss that may be broadly applicable to other neurodegenerative diseases. VIDEO ABSTRACT.

Mice expressing the variant rs1143679 allele of ITGAM (CD11b) show impaired DC-mediated T cell proliferation

Genome-wide association studies (GWAS) and functional genomic analyses have implicated several ITGAM (CD11b) single-nucleotide polymorphisms (SNPs) in the development of SLE and other disorders. ITGAM encodes the α_M chain of the β₂ integrin Mac-1, a receptor that plays important roles in myeloid cell functions. The ITGAM SNP rs1143679, which results in an arginine to histidine change at amino acid position 77 of the CD11b protein, has been shown to reduce binding to several ligands and to alter Mac-1-mediated cellular response in vitro. Importantly, however, the potential contribution of this SNP variant to the initiation and/or progression of immune and inflammatory processes in vivo remains unexplored. Herein, we describe for the first time the generation and characterization of a mouse line expressing the 77His variant of CD11b. Surprisingly, we found that 77His did not significantly affect Mac-1-mediated leukocyte migration and activation as assessed using thioglycollate-induced peritonitis and LPS/TNF-α-induced dermal inflammation models. In contrast, expression of this variant did alter T cell immunity, as evidenced by significantly reduced proliferation of ovalbumin (OVA)-specific transgenic T cells in 77His mice immunized with OVA. Reduced antigen-specific T cell proliferation was also observed when either 77His splenic dendritic cells (DCs) or bone marrow-derived DCs were used as antigen-presenting cells (APCs). Although more work is necessary to determine how this alteration might influence the development of SLE or other diseases, these in vivo findings suggest that the 77His variant of CD11b can compromise the ability of DCs to induce antigen-driven T cell proliferation.

Effects of intestinal nematode treatment on CD11b activation state in an EAE mouse model of multiple sclerosis

The experimental autoimmune encephalomyelitis (EAE) animal model of Multiple Sclerosis (MS) is characterized by episodic neurologic dysfunction arising as a consequence of perivascular mononuclear cell infiltration and demyelination in the CNS. Leukocyte integrins, which are responsible for migration through the endothelial, play key roles in the pathogenesis of autoimmune diseases and chronic inflammation. Intestinal infection of mice with Heligmosomoides polygyrus appears to target CD11b (integrin αM), which is highly expressed on myeloid cells and is critical for their migration and function. H. polygyrus infection induces suppression of ongoing experimental EAE and extensive infiltration of CD11b⁺ cells to the CNS. Therefore, the aim of the present study was to characterize the phenotype and activity of CD11b⁺ cells accompanying the tissue phase infection of L4 H. polygyrus in EAE mice. It was found that the cells displayed a CD11b⁺ state with a distinct phenotype characterised by the expression of co-stimulatory CD80/CD86, CD40, MHCII, F4/80 and the mannose receptor CD206. This activation state illustrates the heterogeneity of CD11b⁺ cells in EAE mice following nematode invasion; these may have important consequences for understanding the effects of CD11b integrin, which is involved in the downregulation of neuroinflammatory disorders.

CD11b-deficient mice exhibit an increased severity in the late phase of antibody transfer-induced experimental epidermolysis bullosa acquisita

CD11b, the α-chain of β₂ integrin Mac-1, is involved in many activation processes of phagocytes. Depending on the respective autoimmune disorder, CD11b has been shown to exert pro-inflammatory functions or be dispensable in their pathogenesis. Here, we investigated the role of CD11b in the pathogenesis of experimental epidermolysis bullosa acquisita (EBA), an autoimmune skin blistering disease mediated by autoantibodies to type VII collagen. Unexpectedly, in an antibody transfer-induced model of EBA, CD11b-deficient mice developed more severe disease symptoms than wild-type mice in the late phase of the disease. Furthermore, as compared to wild-type controls, CD11b-deficient mice expressed increased levels of circulating IFN-γ and IL-4. Taken together, for the first time, our results suggest an anti-inflammatory role for CD11b in experimental autoimmune diseases.

Loss of HDAC11 ameliorates clinical symptoms in a multiple sclerosis mouse model

In an animal model for multiple sclerosis, the absence of HDAC11 reduces clinical severity, spinal cord demyelination, and immune cell infiltration, suggesting that HDAC11 is a promising target for MS treatment.

Multiple sclerosis (MS) is a chronic, immune-mediated, demyelinating disease of the central nervous system (CNS). There is no known cure for MS, and currently available drugs for managing this disease are only effective early on and have many adverse side effects. Results from recent studies suggest that histone deacetylase (HDAC) inhibitors may be useful for the treatment of autoimmune and inflammatory diseases such as MS. However, the underlying mechanisms by which HDACs influence immune-mediated diseases such as MS are unclear. More importantly, the question of which specific HDAC(s) are suitable drug targets for the potential treatment of MS remains unanswered. Here, we investigate the functional role of HDAC11 in experimental autoimmune encephalomyelitis, a mouse model for MS. Our results indicate that the loss of HDAC11 in KO mice significantly reduces clinical severity and demyelination of the spinal cord in the post-acute phase of experimental autoimmune encephalomyelitis. The absence of HDAC11 leads to reduced immune cell infiltration into the CNS and decreased monocytes and myeloid DCs in the chronic progressive phase of the disease. Mechanistically, HDAC11 controls the expression of the pro-inflammatory chemokine C–C motif ligand 2 (CCL2) gene by enabling the binding of PU.1 transcription factor to the CCL2 promoter. Our results reveal a novel pathophysiological function for HDAC11 in CNS demyelinating diseases, and warrant further investigations into the potential use of HDAC11-specific inhibitors for the treatment of chronic progressive MS.

Immunomodulatory effects of a rationally designed peptide mimetic of human IFNβ in EAE model of multiple sclerosis

The efficiency of interferon beta (IFNβ)-based drugs is considerably limited due to their undesirable properties, especially high immunogenicity. In this study, for the first time we investigated the impact of a computationally designed peptide mimetic of IFNβ, called MSPEP27, in the animal model of MS. A peptide library was constructed using the Rosetta program based on the predominant IFNAR1-binding site of IFNβ. Molecular docking studies were carried out using ClusPro and HADDOCK tools. The GROMACS package was subsequently used for molecular dynamics (MD) simulations. Validation of peptide-receptor interaction was carried out using intrinsic fluorescence measurements. To explore in silico findings further, experimental autoimmune encephalomyelitis (EAE) was induced by subcutaneous immunization of myelin oligodendrocyte glycoprotein (MOG35-55). Mice were then separated into distinct groups and intravenously received 10 or 20mgkg^-1 of MSPEP27 or IFNβ. The inflammatory mediators were monitored by immunohistochemistry (IL17, CD11b, CD45), quantitative real-time PCR (MMP2, MMP9, TIMP-1) and enzyme-linked immunosorbent assay (IL1β, TNFα) methods. Among the library of tolerated peptides, MSPEP27, a peptide with favorable physicochemical properties, was chosen for further experiments. This peptide was shown to significantly interact with IFNAR1 in a dose-dependent manner. Like IFNβ, MSPEP27 could efficiently bind to IFNAR1 and form a stable peptide-receptor complex during 30ns MD simulations. In vivo analyses revealed that MSPEP27 could lessen inflammation by modulating the levels of inflammatory mediators. According to our results, MSPEP27 peptide could efficiently bind to IFNAR1 and suppress neuroinflammation in vivo. We conclude that MSPEP27 has protective effects against MOG-induced EAE via reduction of immune dysfunction and inflammation.

Th17 cells, γδ T cells and their interplay in EAE and multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis (MS) that shares many features with the human disease. This review will focus on the role of IL-17-secreting CD4 and γδ T cells in EAE and MS, the plasticity of Th17 cells in vivo and the application of these findings to the understating of the pathogenesis and the development of new treatments for MS. There is convincing evidence that IL-17-secreting CD4 T cells (Th17 cells) and IL-17-secreting γδ T cells play a critical pathogenic role in central nervous system (CNS) inflammation in EAE and MS. Indeed a significant number of the major discoveries on the pathogenic role of IL-17-secreting T cells in autoimmunity were made in the EAE model. These included the first demonstration that IL-23-activated IL-17-secreting T cells are the key T cells in driving autoimmune disease pathology. Although the early studies on IL-17 focused on Th17 cells, it was later demonstrated that γδ T cells were an important early source of IL-17 and IL-21 that helped amplify IL-17 production by Th17 cells in autoimmune diseases. Furthermore, it emerged that Th1 cells can also have encephalitogenic activity and that there was considerable plasticity in these T cell responses, with Th17 cells reverting to a Th1 phenotype in vivo. This questioned the pathogenic role of IL-17 and suggested that other cytokines, such as IFN-γ, GM-CSF and TNF, may be important. Nevertheless, biological drugs that target the IL-23-IL-17 pathway are highly effective in treating human psoriasis and are showing promise in the treatment of relapsing remitting MS and other T-cell mediated autoimmune diseases.

Non-identical twins: Different faces of CR3 and CR4 in myeloid and lymphoid cells of mice and men

Integrins are cell membrane receptors that are involved in essential physiological and serious pathological processes. Their main role is to ensure a closely regulated link between the extracellular matrix and the intracellular cytoskeletal network enabling cells to react to environmental stimuli. Complement receptor type 3 (CR3, αMβ₂, CD11b/CD18) and type 4 (CR4, αXβ₂, CD11c/CD18) are members of the β₂-integrin family expressed on most white blood cells. Both receptors bind multiple ligands like iC3b, ICAM, fibrinogen or LPS. β₂-integrins are accepted to play important roles in cellular adhesion, migration, phagocytosis, ECM rearrangement and inflammation. Several pathological conditions are linked to the impaired functions of these receptors. CR3 and CR4 are generally thought to mediate overlapping functions in monocytes, macrophages and dendritic cells, therefore the potential distinctive role of these receptors has not been investigated so far in satisfactory details. Lately it has become clear that a functional segregation has evolved between the two receptors regarding phagocytosis, cellular adhesion and podosome formation. In addition to their tasks on myeloid cells, the expression and function of CR3 and CR4 on lymphocytes have also gained interest recently. The picture is further complicated by the fact that while these β₂-integrins are expressed by immune cells both in mice and humans, there are significant differences in their expression level, functions and the pathological consequences of genetic defects. Here we aim to summarize our current knowledge on CR3 and CR4 and highlight the functional differences between these receptors, involving their expression in myeloid and lymphoid cells of both men and mice.

Sex Bias in Pathogenesis of Autoimmune Neuroinflammation: Relevance for Dimethyl Fumarate Immunomodulatory/Anti-oxidant Action

In the present study, upon showing sexual dimorphism in dimethyl fumarate (DMF) efficacy to moderate the clinical severity of experimental autoimmune encephalomyelitis (EAE) in Dark Agouti rats, cellular and molecular substrate of this dimorphism was explored. In rats of both sexes, DMF administration from the day of immunization attenuated EAE severity, but this effect was more prominent in males leading to loss of the sexual dimorphism observed in vehicle-administered controls. Consistently, in male rats, DMF was more efficient in diminishing the number of CD4+ T lymphocytes infiltrating spinal cord (SC) and their reactivation, the number of IL-17+ T lymphocytes and particularly cellularity of their highly pathogenic IFN-γ+GM-CSF+IL-17+ subset. This was linked with changes in SC CD11b+CD45+TCRαβ- microglia/proinflammatory monocyte progeny, substantiated in a more prominent increase in the frequency of anti-inflammatory phygocyting CD163+ cells and the cells expressing high surface levels of immunoregulatory CD83 molecule (associated with apoptotic cells phagocytosis and implicated in downregulation of CD4+ T lymphocyte reactivation) among CD11b+CD45+TCRαβ- cells in male rat SC. These changes were associated with greater increase in the nuclear factor (erythroid-derived 2)-like 2 expression in male rats administered with DMF. In accordance with the previous findings, DMF diminished reactive nitrogen and oxygen species generation and consistently, SC level of advanced oxidation protein products, to the greater extent in male rats. Overall, our study indicates sex-specificity in the sensitivity of DMF cellular and molecular targets and encourages sex-based clinical research to define significance of sex for action of therapeutic agents moderating autoimmune neuroinflammation-/oxidative stress-related nervous tissue damage.

Lumican negatively controls the pathogenicity of murine encephalitic TH17 cells

TH17 cells play an essential role in the development of both human multiple sclerosis and animal experimental autoimmune encephalomyelitis (EAE). Nevertheless, it is not well understood how the pathogenicity of TH17 cells is controlled in the autoimmune neuroinflammation. In vitro, we found Lumican (Lum), an extracellular matrix (ECM) protein, is selectively expressed by TH17 cells among tested murine TH subsets. Lum deficiency leads to earlier onset and enhanced severity of EAE. This enhanced disease in Lum-deficient mice is associated with increased production of IL-17 and IL-21 and decreased TH17 cell apoptosis. Dysregulation in cytokine production appears to be specific to TH17 cells as TH1 and TH2 cell polarization and/or cytokine production were unaltered. Furthermore, adoptive transfer of myelin oligodendrocyte glycoprotein specific TH17 cells derived from Lum-deficient mice led to earlier onset and increased severity of disease compared to controls highlighting a TH17-cell-intrinsic effect of Lum. Taken together, our results suggest that Lum negatively regulates encephalitic TH17 cells, implicating a potential therapeutic pathway in TH17 cell mediated autoimmune and inflammatory diseases.

Tanshinone IIA attenuates experimental autoimmune encephalomyelitis in rats

Multiple sclerosis (MS) is an inflammatory autoimmune neurodegenerative disease, which features focal demyelination and inflammatory cell infiltration of the brain and the spinal cord. Tanshinone IIA (TSIIA), one of the major fat‑soluble components of Salvia miltiorrhiza (Danshen), has anti‑inflammatory, immunoregulatory and neuroprotective activity; however, its efficacy in MS remains unknown. The current study was designed to investigate the potential therapeutic function of TSIIA on MS in the experimental autoimmune encephalomyelitis (EAE) rat model. In comparison to the vehicle control group, the TSIIA‑treated groups showed notably improved clinical symptoms and pathological changes, including central nervous system inflammatory cell infiltration and demyelination. Following administration of TSIIA, the quantity of CD4+ T cells, CD8+ T cells and macrophages/microglia in the spinal cord were reduced to different extents. Furthermore, TSIIA was also shown to downregulate interleukin (IL)‑17 and IL‑23 levels in the brain and serum of EAE rats. The results collectively provide evidence that TSIIA alleviates EAE and support its utility as a novel therapy for MS.

Pilot Study of Natural Killer Cells in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis and Multiple Sclerosis

Patients with chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) and multiple sclerosis (MS) suffer from debilitating fatigue which is not alleviated by rest. In addition to the fatigue-related symptoms suffered by patients with CFS/ME and MS, dysfunction of the immune system and, in particular, reduced natural killer (NK) cell cytotoxic activity has also been reported in CFS/ME and MS. The purpose of this pilot study was to compare NK cellular mechanisms in patients with CFS/ME and MS to investigate potential dysfunctions in the NK cell activity pathway. Flow cytometry protocols assessed CD56(dim) CD16(+) and CD56(bright) CD16(+/-) NK cell expression of adhesion molecules, NK activating and inhibiting receptors, NK cell maturation and lytic proteins. All participants in this study were female and included 14 patients with CFS/ME, nine patients with MS and 19 non-fatigued controls. The patient groups and the non-fatigued controls were not taking any immunosuppressive or immune-enhancing medications. In the MS cohort, KIR2DL5 was significantly increased on CD56(bright) CD16(+/-) NK cells and expression of CD94 was significantly increased on CD56(dim) CD16(+) NK cells in comparison with the controls. Co-expression of CD57 and perforin was significantly increased on CD56(dim) CD16(+) NK cells from patients with CFS/ME compared to the MS and non-fatigued control participants. The results from this pilot study suggest that NK cells from patients with CFS/ME and MS may have undergone increased differentiation in response to external stimuli which may affect different mechanisms in the NK cell cytotoxic activity pathway.

Complement receptor 3 mediates renal protection in experimental C3 glomerulopathy

C3 glomerulopathy is a complement-mediated renal disease that is frequently associated with abnormalities in regulation of the complement alternative pathway. Mice with deficiency of factor H (Cfh^–/–), a negative alternative pathway regulator, are an established experimental model of C3 glomerulopathy in which complement C3 fragments including iC3b accumulate along the glomerular basement membrane. Here we show that deficiency of complement receptor 3 (CR3), the main receptor for iC3b, enhances the severity of spontaneous renal disease in Cfh^–/– mice. This effect was found to be dependent on CR3 expression on bone marrow–derived cells. CR3 also mediated renal protection outside the setting of factor H deficiency, as shown by the development of enhanced renal injury in CR3-deficient mice during accelerated nephrotoxic nephritis. The iC3b–CR3 interaction downregulated the proinflammatory cytokine response of both murine and human macrophages to lipopolysaccharide stimulation in vitro, suggesting that the protective effect of CR3 on glomerular injury was mediated via modulation of macrophage-derived proinflammatory cytokines. Thus, CR3 has a protective role in glomerulonephritis and suggests that pharmacologic potentiation of the macrophage CR3 interaction with iC3b could be therapeutically beneficial.

Leukocyte integrins: role in leukocyte recruitment and as therapeutic targets in inflammatory disease

Infection or sterile inflammation triggers site-specific attraction of leukocytes. Leukocyte recruitment is a process comprising several steps orchestrated by adhesion molecules, chemokines, cytokines and endogenous regulatory molecules. Distinct adhesive interactions between endothelial cells and leukocytes and signaling mechanisms contribute to the temporal and spatial fine-tuning of the leukocyte adhesion cascade. Central players in the leukocyte adhesion cascade include the leukocyte adhesion receptors of the β2-integrin family, such as the αLβ2 and αMβ2 integrins, or of the β1-integrin family, such as the α4β1-integrin. Given the central involvement of leukocyte recruitment in different inflammatory and autoimmune diseases, the leukocyte adhesion cascade in general, and leukocyte integrins in particular, represent key therapeutic targets. In this context, the present review focuses on the role of leukocyte integrins in the leukocyte adhesion cascade. Experimental evidence that has implicated leukocyte integrins as targets in animal models of inflammatory disorders, such as experimental autoimmune encephalomyelitis, psoriasis, inflammatory bone loss and inflammatory bowel disease as well as preclinical and clinical therapeutic applications of antibodies that target leukocyte integrins in various inflammatory disorders are presented. Finally, we review recent findings on endogenous inhibitors that modify leukocyte integrin function, which could emerge as promising therapeutic targets.

Long-term impact of neonatal inflammation on demyelination and remyelination in the central nervous system

Perinatal inflammation causes immediate changes of the blood-brain barrier (BBB) and thus may have different consequences in adult life including an impact on neurological diseases such as demyelinating disorders. In order to determine if such a perinatal insult affects the course of demyelination in adulthood as "second hit," we simulated perinatal bacterial inflammation by systemic administration of lipopolysaccharide (LPS) to either pregnant mice or newborn animals. Demyelination was later induced in adult animals by cuprizone [bis(cyclohexylidenehydrazide)], which causes oligodendrocyte death with subsequent demyelination accompanied by strong microgliosis and astrogliosis. A single LPS injection at embryonic day 13.5 did not have an impact on demyelination in adulthood. In contrast, serial postnatal LPS injections (P0-P8) caused an early delay of myelin removal in the corpus callosum, which was paralleled by reduced numbers of activated microglia. During remyelination, postnatal LPS treatment enhanced early remyelination with a concomitant increase of mature oligodendrocytes. Furthermore, the postnatal LPS challenge impacts the phenotype of microglia since an elevated mRNA expression of microglia related genes such as TREM 2, CD11b, TNF-α, TGF-β1, HGF, FGF-2, and IGF-1 was found in these preconditioned mice during early demyelination. These data demonstrate that postnatal inflammation has long-lasting effects on microglia functions and modifies the course of demyelination and remyelination in adulthood.

Early treatment with anti-VLA-4 mAb can prevent the infiltration and/or development of pathogenic CD11b+CD4+ T cells in the CNS during progressive EAE

Natalizumab is a humanized monoclonal antibody against the leukocyte adhesion molecule very late antigen (VLA)-4, and is currently an approved therapy for patients with relapsing-remitting multiple sclerosis (RRMS). However, it is unknown whether natalizumab is beneficial for progressive forms of MS. Therefore, we assessed the effects of anti-VLA-4 monoclonal antibody (mAb) therapy in a progressive experimental autoimmune encephalomyelitis (EAE) mouse model. Notably, we found that early therapy could significantly reduce the severity of progressive EAE, while treatment initiated at an advanced stage was less efficient. Furthermore, we observed the accumulation of a novel subset of GM-CSF-producing CD11b+CD4+ T cells in the CNS throughout disease progression. Importantly, early therapeutic anti-VLA-4 mAb treatment suppressed the accumulation of these GM-CSF-producing CD11b+CD4+ T cells in the CNS along with activated microglia/macrophages populations, and also conferred a protective effect against inflammation-mediated neurodegeneration, including demyelination and axonal loss. Collectively, our data suggest that early treatment with anti-VLA-4 mAb can provide neuroprotection against progressive CNS autoimmune disease by preventing the accumulation of pathogenic GM-CSF-producing CD11b+CD4+ T cells in the CNS.

Integrin CD11b positively regulates TLR4-induced signalling pathways in dendritic cells but not in macrophages

Tuned and distinct responses of macrophages and dendritic cells to Toll-like receptor 4 (TLR4) activation induced by lipopolysaccharide (LPS) underpin the balance between innate and adaptive immunity. However, the molecule(s) that confer these cell-type-specific LPS-induced effects remain poorly understood. Here we report that the integrin α(M) (CD11b) positively regulates LPS-induced signalling pathways selectively in myeloid dendritic cells but not in macrophages. In dendritic cells, which express lower levels of CD14 and TLR4 than macrophages, CD11b promotes MyD88-dependent and MyD88-independent signalling pathways. In particular, in dendritic cells CD11b facilitates LPS-induced TLR4 endocytosis and is required for the subsequent signalling in the endosomes. Consistent with this, CD11b deficiency dampens dendritic cell-mediated TLR4-triggered responses in vivo leading to impaired T-cell activation. Thus, by modulating the trafficking and signalling functions of TLR4 in a cell-type-specific manner CD11b fine tunes the balance between adaptive and innate immune responses initiated by LPS.

Sleep and behavior during vesicular stomatitis virus induced encephalitis in BALB/cJ and C57BL/6J mice

Intranasal application of vesicular stomatitis virus (VSV) produces a well-characterized model of viral encephalitis in mice. Within one day post-infection (PI), VSV travels to the olfactory bulb and, over the course of 7 days, it infects regions and tracts extending into the brainstem followed by clearance and recovery in most mice by PI day 14 (PI 14). Infectious diseases are commonly accompanied by excessive sleepiness; thus, sleep is considered a component of the acute phase response to infection. In this project, we studied the relationship between sleep and VSV infection using C57BL/6 (B6) and BALB/c mice. Mice were implanted with transmitters for recording EEG, activity and temperature by telemetry. After uninterrupted baseline recordings were collected for 2 days, each animal was infected intranasally with a single low dose of VSV (5×10(4) PFU). Sleep was recorded for 15 consecutive days and analyzed on PI 0, 1, 3, 5, 7, 10, and 14. Compared to baseline, amounts of non-rapid eye movement sleep (NREM) were increased in B6 mice during the dark period of PI 1-5, whereas rapid eye movement sleep (REM) was significantly reduced during the light periods of PI 0-14. In contrast, BALB/c mice showed significantly fewer changes in NREM and REM. These data demonstrate sleep architecture is differentially altered in these mouse strains and suggests that, in B6 mice, VSV can alter sleep before virus progresses into brain regions that control sleep.

Discovery of novel disease-specific and membrane-associated candidate markers in a mouse model of multiple sclerosis

Multiple sclerosis is a chronic demyelinating disorder characterized by the infiltration of auto-reactive immune cells from the periphery into the central nervous system resulting in axonal injury and neuronal cell death. Experimental autoimmune encephalomyelitis represents the best characterized animal model as common clinical, histological, and immunological features are recapitulated. A label-free mass spectrometric proteomics approach was used to detect differences in protein abundance within specific fractions of disease-affected tissues including the soluble lysate derived from the spinal cord and membrane protein-enriched peripheral blood mononuclear cells. Tissues were harvested from actively induced experimental autoimmune encephalomyelitis mice and sham-induced ("vehicle" control) counterparts at the disease peak followed by subsequent analysis by nanoflow liquid chromatography tandem mass spectrometry. Relative protein quantitation was performed using both intensity- and fragmentation-based approaches. After statistical evaluation of the data, over 500 and 250 differentially abundant proteins were identified in the spinal cord and peripheral blood mononuclear cell data sets, respectively. More than half of these observations have not previously been linked to the disease. The biological significance of all candidate disease markers has been elucidated through rigorous literature searches, pathway analysis, and validation studies. Results from comprehensive targeted mass spectrometry analyses have confirmed the differential abundance of ∼ 200 candidate markers (≥ twofold dysregulated expression) at a 70% success rate. This study is, to our knowledge, the first to examine the cell-surface proteome of peripheral blood mononuclear cells in experimental autoimmune encephalomyelitis. These data provide a unique mechanistic insight into the dynamics of peripheral immune cell infiltration into CNS-privileged sites at a molecular level and has identified several candidate markers, which represent promising targets for future multiple sclerosis therapies. The mass spectrometry proteomics data associated with this manuscript have been deposited to the ProteomeXchange Consortium with the data set identifier PXD000255.

MicroRNA regulate immune pathways in T-cells in multiple sclerosis (MS)

Background

MicroRNA are small noncoding RNA molecules that are involved in the control of gene expression. To investigate the role of microRNA in multiple sclerosis (MS), we performed genome-wide expression analyses of mRNA and microRNA in T-cells from MS patients and controls.

Methods

Heparin-anticoagulated peripheral blood was collected from MS-patients and healthy controls followed by isolation of T-cells. MicroRNA and RNA from T-cells was prepared and hybridized to Affymetrix miR 2.0 array and Affymetrix U133Plus 2.0 Human Genome array (Santa Clara, CA), respectively. Verifications were performed with real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA).

Results

We identified 2,452 differentially expressed genes and 21 differentially expressed microRNA between MS patients and controls. By Kolmogorov-Smirnov test, 20 of 21 differentially expressed microRNA were shown to affect the expression of their target genes, many of which were involved in the immune system. Tumor necrosis factor ligand superfamily member 14 (TNFSF14) was a microRNA target gene significantly decreased in MS. The differential expression of mir-494, mir-197 and the predicted microRNA target gene TNFSF14 was verified by real-time PCR and ELISA.

Conclusion

These findings indicate that microRNA may be important regulatory molecules in T-cells in MS.

Platelets and neurovascular inflammation

Platelets participate in haemostasis and in thrombus formation in health and disease. Moreover, they contribute to inflammation and cooperate with immune cells in a magnitude of inflammatory/immune responses. Although the inflammatory response has been recognised to be critical in neuronal diseases such as Alzheimer's disease or multiple sclerosis and its mouse counterpart, experimental autoimmune encephalomyelitis, the participation of platelets in these diseases is poorly investigated so far. Emerging studies, however, point to an interesting crosstalk between platelets and neuroinflammation. For instance, when the integrity of the blood brain barrier is compromised, platelets may be relevant for endothelial inflammation, as well as recruitment and activation of inflammatory cells, thereby potentially contributing to central nervous tissue pathogenesis. This review summarises recent insights in the role of platelets for neurovascular inflammation and addresses potential underlying mechanisms, by which platelets may affect the pathophysiology of neurovascular diseases.

Role of LFA-1 in the activation and trafficking of T cells: implications in the induction of chronic colitis

INTRODUCTION

We have previously demonstrated that adoptive transfer of naïve CD4(+) T cells devoid of lymphocyte function-associated antigen-1-deficient (LFA-1; CD11a/CD18) into recombination activating gene-1 (RAG-1) deficient (RAG(-/-) ) mice fails to induce chronic colitis whereas transfer of wild type (WT) T-cells induces unrelenting and chronic disease.

METHODS

The objectives of this study were to assess the role of lymphocyte function-associated antigen-1 (LFA-1) in enteric antigen (EAg)-induced activation of T cells in vitro and in vivo and to define the importance of this integrin in promoting trafficking of T cells to the mesenteric lymph nodes (MLNs) and colon.

RESULTS

We found that EAg-pulsed dendritic cells (DCs) induced proliferation of LFA-1-deficient (CD11a(-/-) ) CD4(+) T cells that was very similar to that induced using WT T cells, suggesting that LFA-1 is not required for activation/proliferation of T cells in vitro. Coculture of WT or CD11a(-/-) T cells with EAg-pulsed DCs induced the generation of similar amounts of interferon-gamma, interleukin (IL)-4, and IL-10, whereas IL-17A production was reduced ≈ 2-fold in cocultures with CD11a(-/-) T cells. Short-term (20-22 hours) trafficking studies demonstrated that while both WT and CD11a(-/-) T cells migrated equally well into the spleen, liver, lungs, small intestine, cecum, and colon, trafficking of CD11a(-/-) T cells to the MLNs was reduced by 50% when compared to WT T cells. When the observation period was extended to 3-7 days posttransfer, we observed ≈ 2-3-fold more WT T cells within the MLNs and colon than CD11a(-/-) T cells, whereas T-cell proliferation (as measured by CFSE dilution) was comparable in both populations.

CONCLUSIONS

Taken together, our data suggest that LFA-1 is not required for EAg-induced activation of CD4(+) T cells in vitro or in vivo but is required for trafficking of T cells to the MLNs and homing of colitogenic effector cells to the colon where they initiate chronic gut inflammation.

Targeted inhibition of complement using complement receptor 2-conjugated inhibitors attenuates EAE

Multiple sclerosis (MS) is the most common autoimmune demyelinating disease, affecting millions of individuals worldwide. In the last two decades, many therapeutic options for the treatment of MS have become available, however they are limited in terms of effectiveness and some remain plagued by safety issues. The currently available treatment options target relapsing remitting forms of MS and are not effective against the more progressive forms of the disease. These limitations highlight a significant unmet treatment need for MS. In experimental autoimmune encephalomyelitis (EAE) studies from our laboratory, we have previously shown, using a number of complement mutant and transgenic mice, that inhibition of the alternative complement pathway and the C3 convertase confers significant protection from disease. We report here that targeted inhibition of complement activation using complement receptor 2 (CR2)-conjugated inhibitors significantly attenuates EAE. Administration of CR2-Crry (blocks all complement pathways at C3 activation) and CR2-fH (specifically blocks the alternative pathway) just prior to and during the onset of EAE blocks progression of both acute and chronic disease. These data indicate that inhibition of complement may offer an effective therapeutic approach to treating both acute and chronic forms of demyelinating disease through blocking the alternative pathway or complement convertases.

The leucocyte β2 (CD18) integrins: the structure, functional regulation and signalling properties

Leucocytes are highly motile cells. Their ability to migrate into tissues and organs is dependent on cell adhesion molecules. The integrins are a family of heterodimeric transmembrane cell adhesion molecules that are also signalling receptors. They are involved in many biological processes, including the development of metazoans, immunity, haemostasis, wound healing and cell survival, proliferation and differentiation. The leucocyte-restricted β2 integrins comprise four members, namely αLβ2, αMβ2, αXβ2 and αDβ2, which are required for a functional immune system. In this paper, the structure, functional regulation and signalling properties of these integrins are reviewed.

Leucocyte recruitment in inflammation and novel endogenous negative regulators thereof

BACKGROUND

The process of extravasation of leucocytes from the vasculature into an infected, inflamed or injured tissue, designated the leucocyte adhesion cascade, is a major process in innate and adaptive immunity. In every immune process, both agonists and inhibitors, that is, positive and negative regulators, exist.

MATERIALS AND METHODS

It was only recently that endogenous inhibitors of the leucocyte adhesion cascade were identified, whereas many selectin, integrin and immunoglobulin superfamily adhesion receptors as well as chemokines and chemokine receptors promoting leucocyte recruitment have been described over the last three decades. Endogenous negative regulators include for instance pentraxin-3 (PTX-3) that blocks selectin-dependent leucocyte rolling, or the endothelium-derived developmental endothelial locus-1 (Del-1) that antagonizes beta2-integrin-mediated firm adhesion of leucocytes to the endothelium.

CONCLUSIONS

As leucocyte infiltration is a major therapeutic target in inflammatory and autoimmune disease, it becomes obvious that such endogenous anti-adhesive and anti-inflammatory agents may represent an attractive novel therapeutic platform for inflammatory and immune disorders. This review focuses on these novel endogenous inhibitors of leucocyte recruitment.

Platelets contribute to the pathogenesis of experimental autoimmune encephalomyelitis

RATIONALE

Multiple sclerosis (MS) and its mouse model, experimental autoimmune encephalomyelitis (EAE), are inflammatory disorders of the central nervous system (CNS). The function of platelets in inflammatory and autoimmune pathologies is thus far poorly defined.

OBJECTIVE

We addressed the role of platelets in mediating CNS inflammation in EAE.

METHODS AND RESULTS

We found that platelets were present in human MS lesions as well as in the CNS of mice subjected to EAE but not in the CNS from control nondiseased mice. Platelet depletion at the effector-inflammatory phase of EAE in mice resulted in significantly ameliorated disease development and progression. EAE suppression on platelet depletion was associated with reduced recruitment of leukocytes to the inflamed CNS, as assessed by intravital microscopy, and with a blunted inflammatory response. The platelet-specific receptor glycoprotein Ibα (GPIbα) promotes both platelet adhesion and inflammatory actions of platelets and targeting of GPIbα attenuated EAE in mice. Moreover, targeting another platelet adhesion receptor, glycoprotein IIb/IIIa (GPIIb/IIIa), also reduced EAE severity in mice.

CONCLUSIONS

Platelets contribute to the pathogenesis of EAE by promoting CNS inflammation. Targeting platelets may therefore represent an important new therapeutic approach for MS treatment.

Absence of β2 integrins impairs regulatory T cells and exacerbates CD4+ T cell-dependent autoimmune carditis

The immunopathogenic mechanisms mediating inflammation in multiorgan autoimmune diseases may vary between the different target tissues. We used the K/BxN TCR transgenic mouse model to investigate the contribution of CD4(+) T cells and β(2) integrins in the pathogenesis of autoimmune arthritis and endocarditis. Depletion of CD4(+) T cells following the onset of arthritis specifically prevented the development of cardiac valve inflammation. Genetic absence of β(2) integrins had no effect on the severity of arthritis and unexpectedly increased the extent of cardiovascular pathology. The exaggerated cardiac phenotype of the β(2) integrin-deficient K/BxN mice was accompanied by immune hyperactivation and was linked to a defect in regulatory T cells. These findings are consistent with a model in which the development of arthritis in K/BxN mice relies primarily on autoantibodies, whereas endocarditis depends on an additional contribution of effector T cells. Furthermore, strategies targeting β(2) integrins for the treatment of systemic autoimmune conditions need to consider not only the role of these molecules in leukocyte recruitment to sites of inflammation, but also their impact on the regulation of immunological tolerance.

Interferon-beta is a key regulator of proinflammatory events in experimental autoimmune encephalomyelitis

BACKGROUND

Interferon (IFN)-β is an effective therapy for relapsing-remitting multiple sclerosis, yet its mechanism of action remains ill-defined.

OBJECTIVES

Our objective was to characterize the role of IFN-β in immune regulation in experimental autoimmune encephalomyelitis (EAE).

METHODS

IFN-β(+/+) and IFN-β(-/-) mice were immunized with myelin oligodendrocyte glycoprotein peptide in the presence or absence of IFN-β, to induce EAE. Disease pathogenesis was monitored in the context of incidence, time of onset, clinical score, and immune cell activation in the brains, spleens and lymph nodes of affected mice.

RESULTS

Compared with IFN-β(+/+) mice, IFN-β(-/-) mice exhibited an earlier onset and a more rapid progression of EAE, increased numbers of CD11b(+) leukocytes infiltrating affected brains and an increased percentage of Th17 cells in the central nervous system and draining lymph nodes. IFN-β treatment delayed disease onset and reduced disease severity. Ex vivo experiments revealed that the lack of IFN-β results in enhanced generation of autoreactive T cells, a likely consequence of the absence of IFN-β-regulated events in both the CD4(+) T cells and antigen-presenting dendritic cells. Gene expression analysis of IFN-β-treated bone marrow macrophages (CD11b(+)) identified modulation of genes affecting T cell proliferation and Th17 differentiation.

CONCLUSIONS

We conclude that IFN-β acts to suppress the generation of autoimmune-inducing Th17 cells during the development of disease as well as modulating pro-inflammatory mediators.

Binding of recombinant T cell receptor ligands (RTL) to antigen presenting cells prevents upregulation of CD11b and inhibits T cell activation and transfer of experimental autoimmune encephalomyelitis

Recombinant T cell ligands (RTLs) ameliorate experimental autoimmune encephalomyelitis (EAE) in an antigen-specific manner. We evaluated effects of RTL401 (I-A(s) alpha1beta1+PLP-139-151) on splenocytes from SJL/J mice with EAE to study RTL-T cell tolerance-inducing mechanisms. RTLs bound to B, macrophages and DCs, through RTL-MHC-alpha1beta1 moiety. RTL binding reduced CD11b expression on splenic macrophages/DC, and RTL401-conditioned macrophages/DC, not B cells, inhibited T cell activation. Reduced ability of RTL- incubated splenocytes to transfer EAE was likely mediated through macrophages/DC, since B cells were unnecessary for RTL treatment of EAE. These results demonstrate a novel pathway of T cell regulation by RTL-bound APCs.

Haptoglobin deficiency facilitates the development of autoimmune inflammation

Haptoglobin (HP) is an acute phase protein synthesized by liver cells in response to IL-6. HP has been demonstrated to modulate the immune response and to have anti-inflammatory activities. To analyze HP's effect on autoimmune inflammation, we here studied the course of EAE induced by immunization of Hp knockout (Hp(-/-)) and syngeneic WT mice with myelin oligodendrocyte glycoprotein peptide (MOG(35-55)). Hp(-/-)mice suffered from a more severe disease that was associated with increased expression of IL-17A, IL-6, and IFN-gamma mRNA in the CNS and with a denser cellular infiltrate in the spinal cord. During the recovery phase, a significantly higher number of myeloid DC, CD8+ cells, IL-17+ CD4+ and IFN-gamma+ CD4+ cells persisted in the CNS of Hp(-/-) mice. Absence of HP affected the priming and differentiation of T cells after MOG(35-55) immunization, as levels of Th2 cytokines produced in response to MOG stimulation by Hp(-/-) T cells were reduced. These results suggest that HP plays a modulatory and protective role on autoimmune inflammation of the CNS.

Immune-mediated CNS damage

Multiple sclerosis (MS) is a demyelinating autoimmune disease. However, the persisting neurological deficits in MS patients result from acute axonal injury and chronic neurodegeneration, which are both triggered by the autoreactive immune response. Innate immunity, mainly mediated by activated microglial cells and invading macrophages, appears to contribute to chronic neurodegeneration. Activated microglia produce several reactive oxygen species and proinflammatory cytokines which affect neuronal function, integrity and survival. Adaptive immunity, particularly in cytotoxic CD8+ T cells, participates in acute demyelination and axonal injury by directly attacking oligodendrocytes and possibly neurons as well. Understanding the mechanisms of immune-mediated neuronal damage might help to design novel therapy strategies for MS.

beta2-integrins in demyelinating disease: not adhering to the paradigm

The beta(2)-integrins are a subfamily of integrins expressed on leukocytes that play an essential role in leukocyte trafficking, activation, and many other functions. Studies in EAE, the animal model for multiple sclerosis, show differential requirements for beta(2)-integrins in this disease model, ranging from critical in the case of LFA-1 (CD11a/CD18) to unimportant in the case of CD11d/CD18. Importantly, expression of beta(2)-integrins on T cell subsets provides some clues as to the function(s) these adhesion molecules play in disease development. For example, transferred EAE studies have shown that Mac-1 (CD11b/CD18) expression on alphabeta T cells is critical for disease development, and the absence of LFA-1 on Tregs in recipient mice results in exacerbated disease. In this review, we summarize recent findings regarding the role of beta(2)-integrins in demyelinating disease and new information about the role of beta(2)-integrins with respect to alterations in Treg numbers and function. In addition, we discuss the potential for targeting beta(2)-integrins in human demyelinating disease in light of the recent animal model studies.