C-type lectin receptors Mcl and Mincle control development of multiple sclerosis-like neuroinflammation.

Pattern recognition receptors (PRRs) are crucial for responses to infections and tissue damage; however, their role in autoimmunity is less clear. Herein we demonstrate that 2 C-type lectin receptors (CLRs) Mcl and Mincle play an important role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Congenic rats expressing lower levels of Mcl and Mincle on myeloid cells exhibited a drastic reduction in EAE incidence. In vivo silencing of Mcl and Mincle or blockade of their endogenous ligand SAP130 revealed that these receptors' expression in the central nervous system is crucial for T cell recruitment and reactivation into a pathogenic Th17/GM-CSF phenotype. Consistent with this, we uncovered MCL- and MINCLE-expressing cells in brain lesions of MS patients and we further found an upregulation of the MCL/MINCLE signaling pathway and an increased response following MCL/MINCLE stimulation in peripheral blood mononuclear cells from MS patients. Together, these data support a role for CLRs in autoimmunity and implicate the MCL/MINCLE pathway as a potential therapeutic target in MS.

Scavenger Receptor A Mediates the Clearance and Immunological Screening of MDA-Modified Antigen by M2-Type Macrophages.

In this study, we investigated the uptake of malondialdehyde (MDA)-modified myelin oligodendrocyte glycoprotein (MOG) in the context of lipid peroxidation and its implications in CNS autoimmunity. The use of custom-produced fluorescently labeled versions of MOG or MDA-modified MOG enabled us to study and quantify the uptake by different macrophage populations and to identify the responsible receptor, namely SRA. The SRA-mediated uptake of MDA-modified MOG is roughly tenfold more efficient compared to that of the native form. Notably, this uptake is most strongly associated with anti-inflammatory M2-type macrophages. MDA-modified MOG was demonstrated to be resistant to degradation by lysine-dependent proteases in vitro, but the overall digestion fragments appeared to be similar in cell lysates, although their relative abundance appeared to be altered as a result of faster uptake. Accordingly, MDA-modified MOG is processed for presentation by APCs, allowing maximized recall proliferation of MOG35-55-specific 2D2 T cells in vitro due to higher uptake. However, MDA modification of MOG did not enhance immune priming or disease course in the in vivo MOG-EAE model, but did induce antibody responses to both MOG and MDA adducts. Taken together our results indicate that MDA adducts primarily constitute clearance signals for phagocytes and promote rapid removal of antigen, which is subjected to immunological screening by previously licensed T cells.

Nitration of MOG diminishes its encephalitogenicity depending on MHC haplotype.

Post-translational modifications of autoantigens are hypothesized to affect their immunogenicity. We here report that nitration of tyrosine 40 in Myelin Oligodendrocyte Glycoprotein (MOG) abrogates its encephalitogenicity both at protein and peptide levels in the experimental autoimmune encephalomyelitis (EAE) model in H2b C57BL/6 mice. Furthermore, nitrated MOG displays inferior antigen-specific proliferation of 2D2 splenocytes in vitro. Conversely, H2q DBA1 mice remain fully susceptible to EAE induction using nitrated MOG as the dominant epitope of H2q mice is unaltered. Molecular modeling analysis of the MOG35-55/H2-IAb complex and bioinformatics peptide binding predictions indicate that the lack of T cell reactivity towards nitrated MOG can be attributed to the inability of murine H2-IAb to efficiently present the altered peptide ligand of MOG35-55 because the nitrated tyrosine 40 cannot be accommodated in the p1 anchor pocket. In conclusion we demonstrate nitration as a relevant determinant affecting T cell recognition of carrier antigen depending on MHC haplotype. Our data have implications for understanding the role of post-translationally modified antigen in autoimmunity.

TGFß regulates persistent neuroinflammation by controlling Th1 polarization and ROS production via monocyte-derived dendritic cells.

Intracerebral levels of Transforming Growth Factor beta (TGFß) rise rapidly during the onset of experimental autoimmune encephalomyelitis (EAE), a mouse model of Multiple Sclerosis (MS). We addressed the role of TGFß responsiveness in EAE by targeting the TGFß receptor in myeloid cells, determining that Tgfbr2 was specifically targeted in monocyte-derived dendritic cells (moDCs) but not in CNS resident microglia by using bone-marrow chimeric mice. TGFß responsiveness in moDCs was necessary for the remission phase since LysM(Cre) Tgfbr2(fl/fl) mice developed a chronic form of EAE characterized by severe demyelination and extensive infiltration of activated moDCs in the CNS. Tgfbr2 deficiency resulted in increased moDC IL-12 secretion that skewed T cells to produce IFN-γ, which in turn enhanced the production of moDC-derived reactive oxygen species that promote oxidative damage and demyelination. We identified SNPs in the human NOX2 (CYBB) gene that associated with the severity of MS, and significantly increased CYBB expression was recorded in PBMCs from both MS patients and from MS severity risk allele rs72619425-A carrying individuals. We thus identify a novel myeloid cell-T cell activation loop active in the CNS during chronic disease that could be therapeutically targeted. GLIA 2016;64:1925-1937.

BAFF-secreting neutrophils drive plasma cell responses during emergency granulopoiesis.

Prolonged infections or adjuvant usage can trigger emergency granulopoiesis (EG), leading to dysregulation in neutrophil blood counts. However, the impact of EG on T and B cell function remains largely unknown. In this study, to address this question, we used a mouse model of neutropenia and studied immune activation after adjuvant administration. The initial neutropenic state fostered an environment of increased dendritic cell activation and T cell-derived IL-17 production. Interestingly, neutropenic lysozyme 2-diphtheria toxin A mice exhibited striking EG and amplified neutrophil recruitment to the lymph nodes (LNs) that was dependent on IL-17-induced prostaglandin activity. The recruited neutrophils secreted a B cell-activating factor that highly accelerated plasma cell generation and antigen-specific antibody production. Reduction of neutrophil functions via granulocyte colony-stimulating factor neutralization significantly diminished plasma cell formation, directly linking EG with the humoral immune response. We conclude that neutrophils are capable of directly regulating T cell-dependent B cell responses in the LN.

Von Willebrand Factor Gene Variants Associate with Herpes simplex Encephalitis.

Herpes simplex encephalitis (HSE) is a rare complication of Herpes simplex virus type-1 infection. It results in severe parenchymal damage in the brain. Although viral latency in neurons is very common in the population, it remains unclear why certain individuals develop HSE. Here we explore potential host genetic variants predisposing to HSE. In order to investigate this we used a rat HSE model comparing the HSE susceptible SHR (Spontaneously Hypertensive Rats) with the asymptomatic infection of BN (Brown Norway). Notably, both strains have HSV-1 spread to the CNS at four days after infection. A genome wide linkage analysis of 29 infected HXB/BXH RILs (recombinant inbred lines-generated from the prior two strains), displayed variable susceptibility to HSE enabling the definition of a significant QTL (quantitative trait locus) named Hse6 towards the end of chromosome 4 (160.89-174Mb) containing the Vwf (von Willebrand factor) gene. This was the only gene in the QTL with both cis-regulation in the brain and included several non-synonymous SNPs (single nucleotide polymorphism). Intriguingly, in human chromosome 12 several SNPs within the intronic region between exon 43 and 44 of the VWF gene were associated with human HSE pathogenesis. In particular, rs917859 is nominally associated with an odds ratio of 1.5 (95% CI 1.11-2.02; p-value = 0.008) after genotyping in 115 HSE cases and 428 controls. Although there are possibly several genetic and environmental factors involved in development of HSE, our study identifies variants of the VWF gene as candidates for susceptibility in experimental and human HSE.

Rat bone marrow-derived dendritic cells generated with GM-CSF/IL-4 or FLT3L exhibit distinct phenotypical and functional characteristics.

Dendritic cells are professional APCs that play a central role in the initiation of immune responses. The limited ex vivo availability of dendritic cells inspires the widespread use of bone marrow-derived dendritic cells as an alternative in research. However, the functional characteristics of bone marrow-derived dendritic cells are incompletely understood. Therefore, we compared functional and phenotypic characteristics of rat bone marrow-derived dendritic cells generated with GM-CSF/IL-4 or FLT3 ligand bone marrow-derived dendritic cells. A comparison of surface markers revealed that FLT3 ligand-bone marrow-derived dendritic cells expressed signal regulatory protein α, CD103, and CD4 and baseline levels of MHC class II, CD40, and CD86, which were highly up-regulated upon stimulation. Conversely, GM-CSF/IL-4-bone marrow-derived dendritic cells constitutively expressed signal regulatory protein α, CD11c, and CD11b but only mildly up-regulated MHC class II, CD40, or CD86 following stimulation. Expression of dendritic cell-associated core transcripts was restricted to FLT3 ligand-bone marrow-derived dendritic cells . GM-CSF/IL-4-bone marrow-derived dendritic cells were superior at phagocytosis but were outperformed by FLT3 ligand-bone marrow-derived dendritic cells at antigen presentation and T cell stimulation in vitro. Stimulated GM-CSF/IL-4-bone marrow-derived dendritic cells secreted more TNF, CCL5, CCL20, and NO, whereas FLT3 ligand-bone marrow-derived dendritic cells secreted more IL-6 and IL-12. Finally, whereas GM-CSF/IL-4-bone marrow-derived dendritic cell culture supernatants added to resting T cell cultures promoted forkhead box p3(+) regulatory T cell populations, FLT3 ligand-bone marrow-derived dendritic cell culture supernatants drove Th17 differentiation. We conclude that rat GM-CSF/IL-4-bone marrow-derived dendritic cells and FLT3 ligand-bone marrow-derived dendritic cells are functionally distinct. Our data support the current rationale that FLT3 ligand-bone marrow-derived dendritic cells mostly resemble classic dendritic cells but comprise additional minor subpopulations, whereas GM-CSF/IL-4-bone marrow-derived dendritic cells resemble monocyte-derived inflammatory dendritic cells (iNOS-positive monocyte-derived cells).

PyTMs: a useful PyMOL plugin for modeling common post-translational modifications.

BACKGROUND: Post-translational modifications (PTMs) constitute a major aspect of protein biology, particularly signaling events. Conversely, several different pathophysiological PTMs are hallmarks of oxidative imbalance or inflammatory states and are strongly associated with pathogenesis of autoimmune diseases or cancers. Accordingly, it is of interest to assess both the biological and structural effects of modification. For the latter, computer-based modeling offers an attractive option. We thus identified the need for easily applicable modeling options for PTMs. RESULTS: We developed PyTMs, a plugin implemented with the commonly used visualization software PyMOL. PyTMs enables users to introduce a set of common PTMs into protein/peptide models and can be used to address research questions related to PTMs. Ten types of modification are currently supported, including acetylation, carbamylation, citrullination, cysteine oxidation, malondialdehyde adducts, methionine oxidation, methylation, nitration, proline hydroxylation and phosphorylation. Furthermore, advanced settings integrate the pre-selection of surface-exposed atoms, define stereochemical alternatives and allow for basic structure optimization of the newly modified residues. CONCLUSION: PyTMs is a useful, user-friendly modelling plugin for PyMOL. Advantages of PyTMs include standardized generation of PTMs, rapid time-to-result and facilitated user control. Although modeling cannot substitute for conventional structure determination it constitutes a convenient tool that allows uncomplicated exploration of potential implications prior to experimental investments and basic explanation of experimental data. PyTMs is freely available as part of the PyMOL script repository project on GitHub and will further evolve. Graphical Abstract PyTMs is a useful PyMOL plugin for modeling common post-translational modifications.