T Follicular Helper Cells Have Distinct Modes of Migration and Molecular Signatures in Naive and Memory Immune Responses

SummaryB helper follicular T (Tfh) cells are critical for long-term humoral immunity. However, it remains unclear how these cells are recruited and contribute to secondary immune responses. Here we show that primary Tfh cells segregate into follicular mantle (FM) and germinal center (GC) subpopulations that display distinct gene expression signatures. Restriction of the primary Tfh cell subpopulation in the GC was mediated by downregulation of chemotactic receptor EBI2. Following collapse of the GC, memory T cells persisted in the outer follicle where they scanned CD169+ subcapsular sinus macrophages. Reactivation and intrafollicular expansion of these follicular memory T cells in the subcapsular region was followed by their extrafollicular dissemination via the lymphatic flow. These data suggest that Tfh cells integrate their antigen-experience history to focus T cell help within the GC during primary responses but act rapidly to provide systemic T cell help after re-exposure to the antigen

Basic science232. Certolizumab pegol prevents pro-inflammatory alterations in endothelial cell function

Background: Cardiovascular disease is a major comorbidity of rheumatoid arthritis (RA) and a leading cause of death. Chronic systemic inflammation involving tumour necrosis factor alpha (TNF) could contribute to endothelial activation and atherogenesis. A number of anti-TNF therapies are in current use for the treatment of RA, including certolizumab pegol (CZP), (Cimzia ®; UCB, Belgium). Anti-TNF therapy has been associated with reduced clinical cardiovascular disease risk and ameliorated vascular function in RA patients. However, the specific effects of TNF inhibitors on endothelial cell function are largely unknown. Our aim was to investigate the mechanisms underpinning CZP effects on TNF-activated human endothelial cells. Methods: Human aortic endothelial cells (HAoECs) were cultured in vitro and exposed to a) TNF alone, b) TNF plus CZP, or c) neither agent. Microarray analysis was used to examine the transcriptional profile of cells treated for 6 hrs and quantitative polymerase chain reaction (qPCR) analysed gene expression at 1, 3, 6 and 24 hrs. NF-κB localization and IκB degradation were investigated using immunocytochemistry, high content analysis and western blotting. Flow cytometry was conducted to detect microparticle release from HAoECs. Results: Transcriptional profiling revealed that while TNF alone had strong effects on endothelial gene expression, TNF and CZP in combination produced a global gene expression pattern similar to untreated control. The two most highly up-regulated genes in response to TNF treatment were adhesion molecules E-selectin and VCAM-1 (q 0.2 compared to control; p > 0.05 compared to TNF alone). The NF-κB pathway was confirmed as a downstream target of TNF-induced HAoEC activation, via nuclear translocation of NF-κB and degradation of IκB, effects which were abolished by treatment with CZP. In addition, flow cytometry detected an increased production of endothelial microparticles in TNF-activated HAoECs, which was prevented by treatment with CZP. Conclusions: We have found at a cellular level that a clinically available TNF inhibitor, CZP reduces the expression of adhesion molecule expression, and prevents TNF-induced activation of the NF-κB pathway. Furthermore, CZP prevents the production of microparticles by activated endothelial cells. This could be central to the prevention of inflammatory environments underlying these conditions and measurement of microparticles has potential as a novel prognostic marker for future cardiovascular events in this patient group. Disclosure statement: Y.A. received a research grant from UCB. I.B. received a research grant from UCB. S.H. received a research grant from UCB. All other authors have declared no conflicts of interes

An inquiry into the regulation of positive selection and differentiation in the germinal centre response

In response to antigenic challenge, the production of high-affinity, antibody secreting plasma cells (PCs) and memory B cells (MBCs) by germinal centres (GCs) confers immunological protection against re-infection by the same pathogen and unpins the efficacy of nearly all vaccines currently in human use. Here, the high-resolution SWHEL B cell transgenic model is combined with a number of gene-knockout and antibody-interference perturbations in order to investigate the role of antigen affinity versus T-cell help in the regulation of positive selection and differentiation in the GC response.SWHEL B cells were adoptively transferred into CD45-congenic recipients and challenged with a low-affinity antigen (HEL3X conjugated to sheep red blood cells). Affinity maturation was observed and measured by flow cytometry, and PCdifferentiation tracked using a Blimp1-GFP reporter mouse. The impact of blocking access to antigen or T-cell help was investigated using depleting or blocking antibodies. As expected, blocking access to antigen during the GC response impaired affinity maturation and almost completely abolished the production of PCs. In stark contrast, and unexpectedly, depleting CD4+ T cells accelerated affinity maturation and had no impact on the production of high-affinity PCs, but rather caused PCs to become trapped in the GC light zone. Using a separate murine system, the surprising observation was made that low-affinity GC B cells present more peptide:MHC-II on their surface compared to high-affinity GC B cells. Taken together, these data are consistent with a model whereby direct competition for antigen-dependent signals, not limiting T-cell help, drives positive selection and differentiation of high-affinity GC B cells into PCs.Additionally, the chemokine receptor CCR6 was found to identify the subpopulation of GC B cells fated to differentiate into MBCs. This CCR6-expressing GC B-cell population was characterised in detail in two murine systems, and a corresponding population of CCR6-expressing MBC precursors was also noted in human tonsils, resolving the longstanding question of how to identify MBC precursors in the GC. Finally, a microarray was performed on human tonsil GCs in order to identify the genes that are most differentially expressed at the earliest stages of commitment to an MBC fate

BioCC: An Openfree Hypertext Bio Community Cluster for Biology

We present an openfree hypertext (also known as wiki) web cluster called BioCC. BioCC is a novel wiki farm that lets researchers create hundreds of biological web sites. The web sites form an organic information network. The contents of all the sites on the BioCC wiki farm are modifiable by anonymous as well as registered users. This enables biologists with diverse backgrounds to form their own Internet bio-communities. Each community can have custom-made layouts for information, discussion,and knowledge exchange. BioCC aims to form an everexpanding network of openfree biological knowledge databases used and maintained by biological experts, students, and general users. The philosophy behind BioCC is that the formation of biological knowledge is best achieved by open-minded individuals freely exchanging information. In the near future, the amount of genomic information will have flooded society. BioCC can be an effective and quickly updated knowledge database system. BioCC uses an opensource wiki system called Mediawiki. However, for easier editing, a modified version of Mediawiki, called Biowiki, has been applied. Unlike Mediawiki, Biowiki uses a WYSIWYG (What You See Is What You Get) text editor. BioCC is under a share-alike license called BioLicense (http://biolicense.org). The BioCC top level site is found at http://bio.ccclose

Resolution of severe ipilimumab-induced hepatitis after antithymocyte globulin therapy

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A novel cause of chronic viral meningoencephalitis: Cache Valley virus.

ObjectiveImmunodeficient patients are particularly vulnerable to neuroinvasive infections that can be challenging to diagnose. Metagenomic next generation sequencing can identify unusual or novel microbes and is therefore well suited for investigating the etiology of chronic meningoencephalitis in immunodeficient patients.MethodsWe present the case of a 34-year-old man with X-linked agammaglobulinemia from Australia suffering from 3 years of meningoencephalitis that defied an etiologic diagnosis despite extensive conventional testing, including a brain biopsy. Metagenomic next generation sequencing of his cerebrospinal fluid and brain biopsy tissue was performed to identify a causative pathogen.ResultsSequences aligning to multiple Cache Valley virus genes were identified via metagenomic next generation sequencing. Reverse transcription polymerase chain reaction and immunohistochemistry subsequently confirmed the presence of Cache Valley virus in the brain biopsy tissue.InterpretationCache Valley virus, a mosquito-borne orthobunyavirus, has only been identified in 3 immunocompetent North American patients with acute neuroinvasive disease. The reported severity ranges from a self-limiting meningitis to a rapidly fatal meningoencephalitis with multiorgan failure. The virus has never been known to cause a chronic systemic or neurologic infection in humans. Cache Valley virus has also never previously been detected on the Australian continent. Our research subject traveled to North and South Carolina and Michigan in the weeks prior to the onset of his illness. This report demonstrates that metagenomic next generation sequencing allows for unbiased pathogen identification, the early detection of emerging viruses as they spread to new locales, and the discovery of novel disease phenotypes. Ann Neurol 2017;82:105-114

Differentiation of germinal center B cells into plasma cells is initiated by high-affinity antigen and completed by Tfh cells

Plasma cells (PCs) derived from germinal centers (GCs) secrete the high-affinity antibodies required for long-term serological immunity. Nevertheless, the process whereby GC B cells differentiate into PCs is uncharacterized, and the mechanism underlying the selective PC differentiation of only high-affinity GC B cells remains unknown. In this study, we show that differentiation into PCs is induced among a discrete subset of high-affinity B cells residing within the light zone of the GC. Initiation of differentiation required signals delivered upon engagement with intact antigen. Signals delivered by T follicular helper cells were not required to initiate differentiation but were essential to complete the differentiation process and drive migration of maturing PCs through the dark zone and out of the GC. This bipartite or two-signal mechanism has likely evolved to both sustain protective immunity and avoid autoantibody production.ISSN:0022-1007ISSN:1540-0069ISSN:1540-953