Search

NK cells are cytotoxic lymphocytes with a key role in limiting tumour metastases. In mice, the NK cell lineage continually expresses high levels of the Inhibitor of DNA-binding 2 (Id2) protein and loss of Id2 is incongruous with their survival due to aberrant E-protein target gene activity. Using novel Id2 and E-protein antibodies that detect both mouse and human proteins, we have extensively characterised Id2 and E-protein expression in murine and human NK cells. We detected clear expression of E2 A and HEB, and to a lesser extent E2-2 in murine NK cells. In contrast HEB appears to be the major E-protein expressed in human NK cells, with minor E2-2 expression and surprisingly, no E2 A detected in primary NK cells nor human NK cell lines. These novel antibodies are also functional in immunofluorescence and immunoprecipitation. Mass spectrometry analysis of Id2 immuno-precipitated from murine NK cells revealed a number of novel associated proteins including several members of the SWI/SNF-related matrix-associated actin-dependent regulator chromatin (SMARC) and Mediator complex (MED) families. Taken together, these data highlight the utility of novel Id2 and E-protein antibodies and caution against mouse models for understanding Id2/E-protein biology in NK cells given their clearly disparate expression patternbetween species.

To optimize immunity to pathogens, B lymphocytes generate plasma cells with functionally diverse antibody isotypes. By lineage tracing single cells within differentiating B cell clones, we identified the heritability of discrete fate controlling mechanisms to inform a general mathematical model of B cell fate regulation. Founder cells highly influenced clonal plasma-cell fate, whereas class switch recombination (CSR) was variegated within clones. In turn, these CSR patterns resulted from independent all-or-none expression of both activation-induced cytidine deaminase (AID) and IgH germline transcription (GLT), with the latter being randomly re-expressed after each cell division. A stochastic model premised on these molecular transition rules accurately predicted antibody switching outcomes under varied conditions in vitro and during an immune response in vivo. Thus, the generation of functionally diverse antibody types follows rules of autonomous cellular programming that can be adapted and modeled for the rational control of antibody classes for potential therapeutic benefit.

Cell death plays an important role during pathogen infections. Here, we report that interferon-γ (IFNγ) sensitizes macrophages to Toll-like receptor (TLR)-induced death that requires macrophage-intrinsic death ligands and caspase-8 enzymatic activity, which trigger the mitochondrial apoptotic effectors, BAX and BAK. The pro-apoptotic caspase-8 substrate BID was dispensable for BAX and BAK activation. Instead, caspase-8 reduced pro-survival BCL-2 transcription and increased inducible nitric oxide synthase (iNOS), thus facilitating BAX and BAK signaling. IFNγ-primed, TLR-induced macrophage killing required iNOS, which licensed apoptotic caspase-8 activity and reduced the BAX and BAK inhibitors, A1 and MCL-1. The deletion of iNOS or caspase-8 limited SARS-CoV-2-induced disease in mice, while caspase-8 caused lethality independent of iNOS in a model of hemophagocytic lymphohistiocytosis. These findings reveal that iNOS selectively licenses programmed cell death, which may explain how nitric oxide impacts disease severity in SARS-CoV-2 infection and other iNOS-associated inflammatory conditions.

Summary: Humoral immune responses are tailored to the invading pathogen through regulation of key transcription factors and their networks. This is critical to establishing effective antibody-mediated responses, yet it is unknown how B cells integrate pathogen-induced signals to drive or suppress transcriptional programs specialized for each class of pathogen. Here, we detail the key role of the transcription factor c-Myb in regulating the T-bet-mediated anti-viral program. Deletion of c-Myb in mature B cells significantly increased serum IgG2c and CXCR3 expression by upregulating T-bet, normally suppressed during Th2-cell-mediated responses. Enhanced expression of T-bet resulted in aberrant plasma cell differentiation within the germinal center, mediated by CXCR3 expression. These findings identify a dual role for c-Myb in limiting inappropriate effector responses while coordinating plasma cell differentiation with germinal center egress. Identifying such intrinsic regulators of specialized antibody responses can assist in vaccine design and therapeutic intervention in B-cell-mediated immune disorders. : Piovesan et al. examine how B cells establish transcriptional programs that result in tailored responses to invading pathogens. The authors find that the transcription factor c-Myb represses the T-bet-mediated anti-viral program in B cells. c-Myb limits inappropriate effector responses while coordinating plasma cell differentiation with germinal center egress. Keywords: B cells, c-Myb, T-bet, immunoglobulin, CXCR3, plasma cell, germinal center

Vitiligo is an autoimmune disease of the skin that results in the destruction of melanocytes and the clinical appearance of white spots. Disease pathogenesis depends on IFN-γ and IFN-γ-induced chemokines to promote T-cell recruitment to the epidermis where melanocytes reside. The skin is a complex organ, with a variety of resident cell types. We sought to better define the microenvironment and distinct cellular contributions during autoimmunity in vitiligo, and we found that the epidermis is a chemokine-high niche in both a mouse model and human vitiligo. Analysis of chemokine expression in mouse skin showed that CXCL9 and CXCL10 expression strongly correlate with disease activity, whereas CXCL10 alone correlates with severity, supporting them as potential biomarkers for following disease progression. Further studies in both our mouse model and human patients showed that keratinocytes were the major chemokine producers throughout the course of disease, and functional studies using a conditional signal transducer and activator of transcription (STAT)-1 knockout mouse showed that IFN-γ signaling in keratinocytes was critical for disease progression and proper autoreactive T-cell homing to the epidermis. In contrast, epidermal immune cell populations including endogenous T cells, Langerhans cells, and γδ T cells were not required. These results have important clinical implications, because topical therapies that target IFN-γ signaling in keratinocytes could be safe and effective new treatments, and skin expression of these chemokines could be used to monitor disease activity and treatment responses.

SUMMARY Following infection, inflammatory cues upregulate core transcriptional programs to establish pathogen-specific protection. In viral infections, T follicular helper (TFH) cells express the prototypical T helper 1 transcription factor T-bet. Several studies have demonstrated essential but conflicting roles for T-bet in TFH biology. Understanding the basis of this controversy is crucial, as modulation of T-bet expression instructs TFH differentiation and ultimately protective antibody responses. Comparing influenza and LCMV viral infections, we demonstrate that the role of T-bet is contingent on the environmental setting of TFH differentiation, IL-2 signaling, and T cell competition. Furthermore, we demonstrate that T-bet expression by either TFH or GC B cells independently drives antibody isotype class switching. Specifically, T cell-specific loss of T-bet promotes IgG1, whereas B cell-specific loss of T-bet inhibits IgG2a/c switching. Combined, this work highlights that the context-dependent induction of T-bet instructs the development of protective, neutralizing antibodies following viral infection or vaccination., In Brief Shiekh et al. show that, in influenza and LCMV infections, the role of the transcription factor T-bet in TFH differentiation is contingent on environmental cues, IL-2 signaling, and T cell competition. Cell-specific T-bet expression independently drives antibody isotype class switching. Therefore T-bet instructs immune protection in a context-dependent manner., Graphical Abstract

Crystallographic studies of ligands bound to biological macromolecules (proteins and nucleic acids) represent\ud an important source of information concerning drug-target interactions, providing atomic level insights\ud into the physical chemistry of complex formation between macromolecules and ligands. Of the\ud more than 115,000 entries extant in the Protein Data Bank (PDB) archive, ~75% include at least one non-polymeric\ud ligand. Ligand geometrical and stereochemical quality, the suitability of ligand models for in silico drug\ud discovery and design, and the goodness-of-fit of ligand models to electron-density maps vary widely across\ud the archive. We describe the proceedings and conclusions from the first Worldwide PDB/Cambridge Crystallographic\ud Data Center/Drug Design Data Resource (wwPDB/CCDC/D3R) Ligand Validation Workshop\ud held at the Research Collaboratory for Structural Bioinformatics at Rutgers University on July 30–31, 2015.\ud Experts in protein crystallography from academe and industry came together with non-profit and for-profit\ud software providers for crystallography and with experts in computational chemistry and data archiving to\ud discuss and make recommendations on best practices, as framed by a series of questions central to structural\ud studies of macromolecule-ligand complexes. What data concerning bound ligands should be archived\ud in the PDB? How should the ligands be best represented? How should structural models of macromoleculeligand\ud complexes be validated? What supplementary information should accompany publications of structural\ud studies of biological macromolecules? Consensus recommendations on best practices developed in\ud response to each of these questions are provided, together with some details regarding implementation.\ud Important issues addressed but not resolved at the workshop are also enumerated.

Summary A defining feature of vertebrate immunity is the acquisition of immunological memory, which confers enhanced protection against pathogens by mechanisms that are incompletely understood. Here, we compared responses by virus-specific naive T cells (T N ) and central memory T cells (T CM ) to viral antigen challenge in lymph nodes (LNs). In steady-state LNs, both T cell subsets localized in the deep T cell area and interacted similarly with antigen-presenting dendritic cells. However, upon entry of lymph-borne virus, only T CM relocalized rapidly and efficiently toward the outermost LN regions in the medullary, interfollicular, and subcapsular areas where viral infection was initially confined. This rapid peripheralization was coordinated by a cascade of cytokines and chemokines, particularly ligands for T CM -expressed CXCR3. Consequently, in vivo recall responses to viral infection by CXCR3-deficient T CM were markedly compromised, indicating that early antigen detection afforded by intranodal chemokine guidance of T CM is essential for efficient antiviral memory.

Previous analyses of the murine and human TSSC6 (also known as Phemx) proteins were not carried out using the full length sequence. Using 5′-RACE and cDNA library screening, we identified an additional 5′ sequence for both the murine Tssc6 cDNA and its human homologue TSSC6. This novel sequence encodes a 5′ exon encoding an in frame, upstream start codon, an N-terminal cytoplasmic domain and a transmembrane domain. The deduced, and now full length, murine and human TSSC6 proteins contained four hydrophobic regions together with other features characteristic of the tetraspanin superfamily. Computational analyses of the full length sequences show that TSSC6 is a genuine, albeit relatively divergent member of this superfamily. Using RNA from a number of mouse tissues, we identified seven splice variants of Tssc6. Splice variants of the human gene were also detected. Tssc6 expression was detected early in embryogenesis in primitive blood cells and was confined to haematopoietic organs in the adult mouse. Tssc6 expression was detected in many haematopoietic cell lines and was highest in cell lines of the erythroid lineage.

Head injury remains a leading cause of death and long-term disability among young people. Prevention of the initial trauma would be the ideal, but in the absence of this we must try to understand the pathophysiological processes leading to secondary brain injuries. This article aims to review the current evidence, looking at both the insults which lead to secondary brain injury and the mechanisms by which the damage occurs. It goes on to look at methods of prevention emphasising that there are some basic principles in the initial treatment that should be followed, which will improve the prognosis of the head injured patient.

Innate lymphoid cell (ILC) populations play a central role in conferring protective immunity at the mucosal frontier. We demonstrate that Transcription factor 7 ( Tcf7 , which encodes Tcf-1), a transcription factor also important for T cell differentiation, is expressed by multiple ILC subsets including ILC2 and NKp46 + ILC3 which confer protection against lung and intestinal inflammation. Tcf-1 was intrinsically required for the differentiation of both ILC2 and NKp46 + ILC3. Loss of Tcf-1 expression impaired the capacity of inflammatory cytokine production IL-5, IL-13 and IL-22 and resulted in crippled responses to intestinal infection with Citrobacter rodentium . Furthermore, a reduction in T-bet expression required for Notch-2-dependent development of NKp46 + ILC3, showed a dose-dependent reduction in Tcf-1 expression. Collectively, our findings demonstrate an essential requirement for Tcf-1 in ILC2 differentiation and reveal a link between Tcf7 , Notch and Tbx21 in NKp46 + ILC3 development.

Crystals of the C2-subunit of crustacyanin have been grown from solutions containing ammonium sulphate and 2-methyl-2,4-pentanediol as co-precipitants. The crystals belong to space group P212121 ( a = 42.0 A , b = 80.9 A , c = 110.8 A ) with two subunits per asymmetric unit and diffract beyond 2.2 A resolution.