Programmed Death-1 Restrains the Germinal Center in Type 1 Diabetes.

Programmed death-1 (PD-1) inhibits T and B cell function upon ligand binding. PD-1 blockade revolutionized cancer treatment, and although numerous patients respond, some develop autoimmune-like symptoms or overt autoimmunity characterized by autoantibody production. PD-1 inhibition accelerates autoimmunity in mice, but its role in regulating germinal centers (GC) is controversial. To address the role of PD-1 in the GC reaction in type 1 diabetes, we used tetramers to phenotype insulin-specific CD4+ T and B cells in NOD mice. PD-1 or PD-L1 deficiency, and PD-1 but not PD-L2 blockade, unleashed insulin-specific T follicular helper CD4+ T cells and enhanced their survival. This was concomitant with an increase in GC B cells and augmented insulin autoantibody production. The effect of PD-1 blockade on the GC was reduced when mice were treated with a mAb targeting the insulin peptide:MHC class II complex. This work provides an explanation for autoimmune side effects following PD-1 pathway inhibition and suggests that targeting the self-peptide:MHC class II complex might limit autoimmunity arising from checkpoint blockade.

Identification of an elaborate NK-specific system regulating HLA-C expression.

The HLA-C gene appears to have evolved in higher primates to serve as a dominant source of ligands for the KIR2D family of inhibitory MHC class I receptors. The expression of NK cell-intrinsic MHC class I has been shown to regulate the murine Ly49 family of MHC class I receptors due to the interaction of these receptors with NK cell MHC in cis. However, cis interactions have not been demonstrated for the human KIR and HLA proteins. We report the discovery of an elaborate NK cell-specific system regulating HLA-C expression, indicating an important role for HLA-C in the development and function of NK cells. A large array of alternative transcripts with differences in intron/exon content are generated from an upstream NK-specific HLA-C promoter, and exon content varies between HLA-C alleles due to SNPs in splice donor/acceptor sites. Skipping of the first coding exon of HLA-C generates a subset of untranslatable mRNAs, and the proportion of untranslatable HLA-C mRNA decreases as NK cells mature, correlating with increased protein expression by mature NK cells. Polymorphism in a key Ets-binding site of the NK promoter has generated HLA-C alleles that lack significant promoter activity, resulting in reduced HLA-C expression and increased functional activity. The NK-intrinsic regulation of HLA-C thus represents a novel mechanism controlling the lytic activity of NK cells during development.

Current strategies exploiting NK-cell therapy to treat haematologic malignancies.

Natural killer (NK) cells recognize targets that have been changed via malignant transformation or infection. Previously, NK cells were thought to be short-lived, but we now know that NK cells can be long-lived and remember past exposures in response to CMV. NK cells use a plethora of activating and inhibitory receptors to recognize these changes and attack targets, but tumour cells often evade NK cells. Therefore, major efforts are being made to hone in on NK cell antitumour properties in immunotherapy. In the clinical setting, haploidentical NK cells can be adoptively transferred to help treat cancer. To expand NK cells in vivo and enhance tumour targeting, IL-15 is being tested in combination with a glycogen synthase kinase (GSK) 3 inhibitor (CHIR99021), an inhibitor that has been shown to expand mature, highly functional NK cells capable of killing multiple tumour targets. One major limitation to NK cell therapy is lack of specificity. To address this concern, bispecific or trispecific engagers that target NK cells to the tumour and an ADAM17 inhibitor that prevents CD16 shedding after NK cell activation are being tested. Additionally, monoclonal antibodies are being designed to redirect the inhibitory signals that limit NK cell functionality. Further understanding of the biology of NK cells will inform strategies to exploit NK cells for therapeutic purposes.

Improving Communication by Standardizing Pediatric Rapid Response Team Documentation.

BACKGROUND: Rapid response teams (RRTs) have been used by multiple hospital systems to enhance patient care and safety. However, processes to document rapid response events (RRE) are often varied among providers and teams, which can lead to suboptimal communication of recommendations to both the primary medical team and family. METHODS: A preintervention chart review was conducted from January-March 2018 and revealed suboptimal baseline documentation following RREs. A literature review and survey of RRT team members led to the creation of a standardized document with an Epic SmartPhrase which included six key elements of RRE documentation: physical examination, intervention performed, response to intervention, plan of care, communication with care team, and communication with family. A postintervention chart review was completed from April-June 2019 to assess improvements in documentation with the use of this SmartPhrase. RESULTS: There were 23 RRE activations in the postintervention period, of which 60.8% were due to respiratory distress. The documentation of the six key elements improved (p < .05) after SmartPhrase creation and serial educational interventions. CONCLUSIONS: Standardized RRE documentation of six key elements significantly improved with the implementation of an Epic SmartPhrase. Improved quality of documentation enhances communication between team members and can contribute to safer patient care.

Identification of trophoblast-specific elements in the HLA-C core promoter.

There are several aspects of HLA-C gene expression that distinguish it from the HLA-A and HLA-B genes. First, HLA-C is expressed by extravillous trophoblasts, whereas HLA-A and HLA-B are not. Second, its cell-surface expression is much lower, which has been linked to changes in transcription and efficiency of peptide loading and export. Third, HLA-C possesses a NK cell-specific promoter and a complex alternative splicing system that regulates expression during NK cell development. In this study, we investigate the contribution of the HLA-C core promoter to trophoblast-specific expression. Analysis of transcription start sites showed the presence of a trophoblast-associated start site and additional upstream TATA and CCAAT-box elements in the HLA-C promoter, suggesting the presence of an overlapping trophoblast-specific promoter. A comparison of in vitro promoter activity showed that the HLA-C promoter was more active in trophoblast cell lines than either the HLA-A or HLA-B promoters. Enhanced trophoblast activity was mapped to the central enhanceosome region of the promoter, and mutational analysis identified changes in the RFX-binding region that generated a trophoblast-specific enhancer.

DNA binding drives the association of BRG1/hBRM bromodomains with nucleosomes.

BRG1 and BRM, central components of the BAF (mSWI/SNF) chromatin remodelling complex, are critical in chromatin structure regulation. Here, we show that the human BRM (hBRM) bromodomain (BRD) has moderate specificity for H3K14ac. Surprisingly, we also find that both BRG1 and hBRM BRDs have DNA-binding activity. We demonstrate that the BRDs associate with DNA through a surface basic patch and that the BRD and an adjacent AT-hook make multivalent contacts with DNA, leading to robust affinity and moderate specificity for AT-rich elements. Although we show that the BRDs can bind to both DNA and H3K14ac simultaneously, the histone-binding activity does not contribute substantially to nucleosome targeting in vitro. In addition, we find that neither BRD histone nor DNA binding contribute to the global chromatin affinity of BRG1 in mouse embryonic stem cells. Together, our results suggest that association of the BRG1/hBRM BRD with nucleosomes plays a regulatory rather than targeting role in BAF activity.

Hypoxia disrupts proteostasis in Caenorhabditis elegans.

Oxygen is fundamentally important for cell metabolism, and as a consequence, O2 deprivation (hypoxia) can impair many essential physiological processes. Here, we show that an active response to hypoxia disrupts cellular proteostasis - the coordination of protein synthesis, quality control, and degradation that maintains the functionality of the proteome. We have discovered that specific hypoxic conditions enhance the aggregation and toxicity of aggregation-prone proteins that are associated with neurodegenerative diseases. Our data indicate this is an active response to hypoxia, rather than a passive consequence of energy limitation. This response to hypoxia is partially antagonized by the conserved hypoxia-inducible transcription factor, hif-1. We further demonstrate that exposure to hydrogen sulfide (H2S) protects animals from hypoxia-induced disruption of proteostasis. H2S has been shown to protect against hypoxic damage in mammals and extends lifespan in nematodes. Remarkably, our data also show that H2S can reverse detrimental effects of hypoxia on proteostasis. Our data indicate that the protective effects of H2S in hypoxia are mechanistically distinct from the effect of H2S to increase lifespan and thermotolerance, suggesting that control of proteostasis and aging can be dissociated. Together, our studies reveal a novel effect of the hypoxia response in animals and provide a foundation to understand how the integrated proteostasis network is integrated with this stress response pathway.