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Autoimmune diseases display a high degree of comorbidity within individuals and families, suggesting shared risk factors. Over the past 15 years, genome-wide association studies have established the polygenic basis of these common conditions and revealed widespread sharing of genetic effects, indicative of a shared immunopathology. Despite ongoing challenges in determining the precise genes and molecular consequences of these risk variants, functional experiments and integration with multimodal genomic data are providing valuable insights into key immune cells and pathways driving these diseases, with potential therapeutic implications. Moreover, genetic studies of ancient populations are shedding light on the contribution of pathogen-driven selection pressures to the increased prevalence of autoimmune disease. This Review summarizes the current understanding of autoimmune disease genetics, including shared effects, mechanisms, and evolutionary origins.

Infection with West Nile Virus (WNV) can drive a wide range of responses, from asymptomatic to flu-like symptoms/fever or severe cases of encephalitis and death. To identify cellular and molecular signatures distinguishing WNV severity, we employed systems profiling of peripheral blood from asymptomatic and severely ill individuals infected with WNV. We interrogated immune responses longitudinally from acute infection through convalescence at 3 months and 1 year employing multiplexed single cell protein and transcriptional profiling (CyTOF and Seq-Well) complemented with matched serum proteomics and metabolomics. At the acute time point, we detected both an elevated proportion of pro-inflammatory markers in innate immune cell types and reduced frequency of regulatory T cell activity in participants with severe infection compared to those with asymptomatic infection. Single-cell transcriptomics of paired samples revealed that asymptomatic donors had higher expression of genes associated with innate immune pathways, in particular anti-inflammatory CD16+monocytes at the acute time point. A multi-omics analysis identified factors--beyond those from individual analyses--that distinguished immune state trajectory between severity groups. Here we highlighted the potential of systems immunology using multiple cell-type and cell-state-specific analyses to identify correlates of infection severity and host cellular activity contributing to an effective anti-viral response.

Maintenance of peripheral tolerance by CD4+Foxp3+ regulatory T cells (Tregs) is essential for regulating autoreactive T cells. The loss of function of Foxp3 leads to autoimmune disease in both animals and humans. An example is the rare, X-linked recessive disorder known as IPEX (Immune Dysregulation, Polyendocrinopathy, Enteropathy X-linked) syndrome. In more common human autoimmune diseases, defects in Treg function are accompanied with aberrant effector cytokines such as IFNγ. It has recently become appreciated that Tregs plays an important role in not only maintaining immune homeostasis but also in establishing the tissue microenvironment and homeostasis of non-lymphoid tissues. Tissue resident Tregs show profiles that are unique to their local environments which are composed of both immune and non-immune cells. Core tissue-residence gene signatures are shared across different tissue Tregs and are crucial to homeostatic regulation and maintaining the tissue Treg pool in a steady state. Through interaction with immunocytes and non-immunocytes, tissue Tregs exert a suppressive function via conventional ways involving contact dependent and independent processes. In addition, tissue resident Tregs communicate with other tissue resident cells which allows Tregs to adopt to their local microenvironment. These bidirectional interactions are dependent on the specific tissue environment. Here, we summarize the recent advancements of tissue Treg studies in both human and mice, and discuss the molecular mechanisms that maintain tissue homeostasis and prevent pathogenesis.

Alzheimer’s disease, the most common age-related neurodegenerative disease, is closely associated with both amyloid-ß plaque and neuroinflammation. Two thirds of Alzheimer’s disease patients are females and they have a higher disease risk. Moreover, women with Alzheimer’s disease have more extensive brain histological changes than men along with more severe cognitive symptoms and neurodegeneration. To identify how sex difference induces structural brain changes, we performed unbiased massively parallel single nucleus RNA sequencing on Alzheimer’s disease and control brains focusing on the middle temporal gyrus, a brain region strongly affected by the disease but not previously studied with these methods. We identified a subpopulation of selectively vulnerable layer 2/3 excitatory neurons that that were RORB-negative and CDH9-expressing. This vulnerability differs from that reported for other brain regions, but there was no detectable difference between male and female patterns in middle temporal gyrus samples. Disease-associated, but sex-independent, reactive astrocyte signatures were also present. In clear contrast, the microglia signatures of diseased brains differed between males and females. Combining single cell transcriptomic data with results from genome-wide association studies (GWAS), we identifiedMERTKgenetic variation as a risk factor for Alzheimer’s disease selectively in females. Taken together, our single cell dataset revealed a unique cellular-level view of sex-specific transcriptional changes in Alzheimer’s disease, illuminating GWAS identification of sex-specific Alzheimer’s risk genes. These data serve as a rich resource for interrogation of the molecular and cellular basis of Alzheimer’s disease.

A small proportion of multiple sclerosis (MS) patients develop new disease activity soon after starting anti-CD20 therapy. This activity does not recur with further dosing, possibly reflecting deeper depletion of CD20-expressing cells with repeat infusions. We assessed cellular immune profiles and their association with transient disease activity following anti-CD20 initiation as a window into relapsing disease biology. Peripheral blood mononuclear cells from independent discovery and validation cohorts of MS patients initiating ocrelizumab were assessed for phenotypic and functional profiles using multiparametric flow cytometry. Pretreatment CD20-expressing T cells, especially CD20 dim CD8 + T cells with a highly inflammatory and central nervous system (CNS)-homing phenotype, were significantly inversely correlated with pretreatment MRI gadolinium-lesion counts, and also predictive of early disease activity observed after anti-CD20 initiation. Direct removal of pretreatment proinflammatory CD20 dim CD8 + T cells had a greater contribution to treatment-associated changes in the CD8 + T cell pool than was the case for CD4 + T cells. Early disease activity following anti-CD20 initiation was not associated with reconstituting CD20 dim CD8 + T cells, which were less proinflammatory compared with pretreatment. Similarly, this disease activity did not correlate with early reconstituting B cells, which were predominantly transitional CD19 + CD24 high CD38 high with a more anti-inflammatory profile. We provide insights into the mode-of-action of anti-CD20 and highlight a potential role for CD20 dim CD8 + T cells in MS relapse biology; their strong inverse correlation with both pretreatment and early posttreatment disease activity suggests that CD20-expressing CD8 + T cells leaving the circulation (possibly to the CNS) play a particularly early role in the immune cascades involved in relapse development.

Genome-wide association studies identifying hundreds of susceptibility loci for autoimmune diseases indicate that genes active in immune cells predominantly mediate risk. However, identification and functional characterization of causal variants remain challenging. Here, we focused on the immunomodulatory role of a protective variant of histone deacetylase 7 (HDAC7). This variant (rs148755202, HDAC7.p.R166H) was identified in a study of low-frequency coding variation in multiple sclerosis (MS). Through transcriptomic analyses, we demonstrate that wild-type HDAC7 regulates genes essential for the function of Foxp3 + regulatory T cells (T regs ), an immunosuppressive subset of CD4 T cells that is generally dysfunctional in patients with MS. Moreover, T reg -specific conditional hemizygous deletion of HDAC7 increased the severity of experimental autoimmune encephalitis (EAE), a mouse model of neuroinflammation. In contrast, T regs transduced with the protective HDAC7 R166H variant exhibited higher suppressive capacity in an in vitro functional assay, mirroring phenotypes previously observed in patient samples. In vivo modeling of the human HDAC7 R166H variant by generation of a knock-in mouse model bearing an orthologous R150H substitution demonstrated decreased EAE severity linked to transcriptomic alterations of brain-infiltrating T regs , as assessed by single-cell RNA sequencing. Our data suggest that dysregulation of epigenetic modifiers, a distinct molecular class associated with disease risk, may influence disease onset. Last, our approach provides a template for the translation of genetic susceptibility loci to detailed functional characterization, using in vitro and in vivo modeling.

Autoimmune diseases, among the most common disorders of young adults, are mediated by genetic and environmental factors. While CD4+Foxp3+regulatory T cells (Tregs) play a central role in preventing autoimmunity, the molecular mechanism underlying their dysfunction is unknown. Here, we performed comprehensive transcriptomic and epigenomic profiling of Tregs in the autoimmune disease multiple sclerosis (MS) to identify central transcriptional programs regulating human autoimmunity. We discovered that upregulation of a primate-specific shortPRDM1isoform (PRDM1-S) inducesSGK1independent from evolutionally conserved longPRDM1, leading to destabilization of Foxp3 and Treg dysfunction. This aberrantPRDM1-S/SGK1axis is shared among other autoimmune diseases. Furthermore, by chromatin landscape profiling in MS Tregs we identified aPRDM1-Sspecificcis-regulatory element associated with enriched binding of AP-1/IRF transcription factors. Our study identifies evolutionally emergedPRDM1-Sand epigenetic priming of AP-1/IRF as key drivers of pathogenic Treg programs leading to human autoimmune disease.

The immune response to SARS-CoV-2 for patients with altered immunity such as hematologic malignancies and autoimmune disease may differ substantially from that in general population. These patients remain at high risk despite wide-spread adoption of vaccination. It is critical to examine the differences at the systems level between the general population and the patients with altered immunity in terms of immunologic and serological responses to COVID-19 infection and vaccination. Here, we developed a novel microfluidic chip for high-plex immuno-serological assay to simultaneously measure up to 50 plasma or serum samples for up to 50 soluble markers including 35 plasma proteins, 11 anti-spike/RBD IgG antibodies spanning all major variants, and controls. Our assay demonstrated the quintuplicate test in a single run with high throughput, low sample volume input, high reproducibility and high accuracy. It was applied to the measurement of 1,012 blood samples including in-depth analysis of sera from 127 patients and 21 healthy donors over multiple time points, either with acute COVID infection or vaccination. The protein association matrix analysis revealed distinct immune mediator protein modules that exhibited a reduced degree of diversity in protein-protein cooperation in patients with hematologic malignancies and patients with autoimmune disorders receiving B cell depletion therapy. Serological analysis identified that COVID infected patients with hematologic malignancies display impaired anti-RBD antibody response despite high level of anti-spike IgG, which could be associated with limited clonotype diversity and functional deficiency in B cells and was further confirmed by single-cell BCR and transcriptome sequencing. These findings underscore the importance to individualize immunization strategy for these high-risk patients and provide an informative tool to monitor their responses at the systems level.

Background Previous studies have identified a large number of distinct microbial taxa that are different between patients with multiple sclerosis (MS) and controls. However, interpretating findings on MS-associated microbiome is challenging as results do not completely concur and studies have included relatively few individuals. To date, it is unclear whether there is a common gut microbial signature in patients with MS across studies. To identity the most common compositional differences of the gut microbiome in MS versus healthy controls, we performed a meta-analysis. This was based on 16S rRNA gene sequences from seven published studies, comprising a total of 524 adult patients with MS and control subjects. Results We found that although alpha and beta diversity did not differ between MS and controls, a lower relative abundance of Prevotella and a dysbiosis of numerous genera within the Clostridia class were reproducibly associated with MS. Additionally, network analysis revealed that the recognized negative Bacteroides-Prevotellacorrelation in controls was disrupted in MS. immunosuppressive agents normalized MS-associated microbiome Prevotella to a similar level as healthy controls. Conclusions Our meta-analysis revealed reproducible gut microbiome signatures in MS across geographically diverse studies. These findings form the basis for future novel therapeutic approaches and possibly enhanced MS recognition/diagnosis by targeting common microbiome signatures.

The increasing availability of single-cell data revolutionizes the understanding of biological mechanisms at cellular resolution. For differential expression analysis in multi-subject single-cell data, negative binomial mixed models account for both subject-level and cell-level overdispersions, but are computationally demanding. Here, we propose an efficient NEgative Binomial mixed model Using a Large-sample Approximation (NEBULA). The speed gain is achieved by analytically solving high-dimensional integrals instead of using the Laplace approximation. We demonstrate that NEBULA is orders of magnitude faster than existing tools and controls false-positive errors in marker gene identification and co-expression analysis. Using NEBULA in Alzheimer’s disease cohort data sets, we found that the cell-level expression of APOE correlated with that of other genetic risk factors (including CLU, CST3, TREM2, C1q, and ITM2B) in a cell-type-specific pattern and an isoform-dependent manner in microglia. NEBULA opens up a new avenue for the broad application of mixed models to large-scale multi-subject single-cell data., The application of negative binomial mixed models (NBMMs) to single-cell data is computationally demanding. To address this issue, Liang He et al. have developed NEBULA, an efficient algorithm that can analyze differential gene expression or co-expression networks in multi-subject single-cell data sets, and validate it on snRNA-seq and scRNA-seq data sets comprising ~200k cells from cohorts of Alzheimer’s disease and multiple sclerosis patients.

Genome-wide association studies (GWAS) have identified genetic susceptibility loci for a variety of autoimmune and inflammatory diseases. These studies confirm the fundamental genetic basis of individual autoimmune diseases, and also point to shared etiological mechanisms across the spectrum of autoimmunity. While hundreds of genetic loci have been implicated in autoimmune diseases, the translation of individual susceptibility loci into specific molecular mechanisms for individual diseases remains difficult. This review highlights recent advances in the genetics of autoimmune disease, and the emerging use of epigenetic techniques to identify pathogenic cell types and causal molecular mechanisms of autoimmunity.

BackgroundBetter understanding of the association between characteristics of patients hospitalized with coronavirus disease 2019 (COVID-19) and outcome is needed to further improve upon patient management.MethodsImmunophenotyping Assessment in a COVID-19 Cohort (IMPACC) is a prospective, observational study of 1164 patients from 20 hospitals across the United States. Disease severity was assessed using a 7-point ordinal scale based on degree of respiratory illness. Patients were prospectively surveyed for 1 year after discharge for post-acute sequalae of COVID-19 (PASC) through quarterly surveys. Demographics, comorbidities, radiographic findings, clinical laboratory values, SARS-CoV-2 PCR and serology were captured over a 28-day period. Multivariable logistic regression was performed.FindingsThe median age was 59 years (interquartile range [IQR] 20); 711 (61%) were men; overall mortality was 14%, and 228 (20%) required invasive mechanical ventilation. Unsupervised clustering of ordinal score over time revealed distinct disease course trajectories. Risk factors associated with prolonged hospitalization or death by day 28 included age ≥ 65 years (odds ratio [OR], 2.01; 95% CI 1.28-3.17), Hispanic ethnicity (OR, 1.71; 95% CI 1.13-2.57), elevated baseline creatinine (OR 2.80; 95% CI 1.63- 4.80) or troponin (OR 1.89; 95% 1.03-3.47), baseline lymphopenia (OR 2.19; 95% CI 1.61-2.97), presence of infiltrate by chest imaging (OR 3.16; 95% CI 1.96-5.10), and high SARS-CoV2 viral load (OR 1.53; 95% CI 1.17-2.00). Fatal cases had the lowest ratio of SARS-CoV-2 antibody to viral load levels compared to other trajectories over time (p=0.001). 589 survivors (51%) completed at least one survey at follow-up with 305 (52%) having at least one symptom consistent with PASC, most commonly dyspnea (56% among symptomatic patients). Female sex was the only associated risk factor for PASC.InterpretationIntegration of PCR cycle threshold, and antibody values with demographics, comorbidities, and laboratory/radiographic findings identified risk factors for 28-day outcome severity, though only female sex was associated with PASC. Longitudinal clinical phenotyping offers important insights, and provides a framework for immunophenotyping for acute and long COVID-19.FundingNIH.

The T cell receptor (TCR) endows T cells with antigen specificity and is central to nearly all aspects of T cell function. Each naïve T cell has a unique TCR sequence that is stably maintained during cell division. In this way, the TCR serves as a molecular barcode that tracks processes such as migration, differentiation, and proliferation of T cells. Recent technological advances have enabled sequencing of the TCR from single cells alongside deep molecular phenotypes on an unprecedented scale. In this review, we discuss strengths and limitations of TCR sequences as molecular barcodes and their application to study immune responses following Programmed Death-1 (PD-1) blockade in cancer. Additionally, we consider applications of TCR data beyond use as a barcode.

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder where recent evidence suggests pathogenesis may be mediated by inflammatory processes. The molecular architecture of the disease remains to be fully elucidated. We performed single-nucleus transcriptomics and unbiased proteomics using postmortem tissue obtained from the prefrontal cortex of 12 individuals with late-stage PD and age-matched controls. We analyzed ∼80,000 nuclei and identified eight major cell types, including brain-resident T cells, each with distinct transcriptional changes in line with the known genetics of PD. By analyzing Lewy body pathology in the same postmortem tissue, we found that α-synuclein pathology is inversely correlated with chaperone expression in excitatory neurons. Examining cell-cell interactions, we found a selective abatement of neuron-astrocyte interactions and enhanced neuroinflammation. Proteomic analyses of the same brains identified synaptic proteins in prefrontal cortex that were preferentially downregulated in PD. Strikingly, comparing this dataset to a regionally similar published analysis for Alzheimer’s disease (AD), we found no common differentially expressed genes in neurons, but identified many shared differentially expressed genes in glial cells, suggesting that disease etiology in PD and AD are likely distinct. These data are presented as a resource for interrogating the molecular and cellular basis of PD and other neurodegenerative diseases.One Sentence SummaryWe provide an extensive single cell analysis profiling nearly 80,000 brain nuclei from prefrontal cortex of late-stage Parkinson’s disease brains, demonstrate that α-synuclein pathology is inversely correlated with chaperone expression in excitatory neurons, found a selective abatement of neuron-astrocyte interactions with enhanced neuroinflammation, and augmented the study with proteomic analysis and cross-comparisons with Alzheimer’s disease datasets, providing valuable insights into the pathways of neurodegeneration and a deep definition of the underlying molecular pathology for Parkinson’s disease.

Background and ObjectiveTo determine whether rituximab is safe and potentially beneficial, warranting further investigation in an efficacy trial for acetylcholine receptor antibody-positive generalized myasthenia gravis (AChR-Ab+ gMG).MethodsThe B-Cell Targeted Treatment in MG (BeatMG) study was a randomized, double-blind, placebo-controlled, multicenter phase 2 trial that utilized a futility design. Individuals 21–90 years of age, with AChR-Ab+ gMG (MG Foundation of America Class II–IV) and receiving prednisone ≥15 mg/d were eligible. The primary outcome was a measure of steroid-sparing effect, defined as the proportion achieving ≥75% reduction in mean daily prednisone dose in the 4-weeks prior to week 52 and with clinical improvement or no significant worsening as compared to the 4-week period prior to randomization. The coprimary outcome was safety. Secondary outcomes included MG-specific clinical assessments. Fifty-two individuals were randomized (1:1) to a 2-cycle rituximab/placebo regimen, with follow-up through 52 weeks.ResultsOf the 52 participants included, mean ± SD age at enrollment was 55.1 ± 17.1 years; 23 (44.2%) were women and 31 (59.6%) were Myasthenia Gravis Foundation of America Class II. The mean ± SD baseline prednisone dose was 22.1 ± 9.7 mg/d. The primary steroid-sparing outcome was achieved in 60% of those on rituximab vs 56% on placebo. The study reached its futility endpoint (p = 0.03), suggesting that the predefined clinically meaningful improvement of 30% due to rituximab over placebo was unlikely to be achieved in a subsequent, larger trial. No safety issues were identified.DiscussionAlthough rituximab was safe and well-tolerated, these results suggest that there is a low probability of observing the defined clinically meaningful steroid-sparing effect over a 12-month period in a phase 3 trial of mild to moderately symptomatic AChR-Ab+ gMG.Classification of EvidenceThis study provides Class I evidence that for mild to moderate AChR-Ab+ gMG, compared with placebo, rituximab is safe but unlikely to reduce steroid use by an absolute difference of at least 30% at 1 year.Trial Registration InformationClinicalTrials.gov identifier: NCT02110706.

The brain is an immune-privileged organ such that immune cell infiltration is highly regulated and better tolerating the introduction of antigen to reduce risk of harmful inflammation. Thus, the composition and the nature of the immune response is fundamentally different in the brain where avoiding immunopathology is prioritized compared to other peripheral organs. While the principle of immune privilege in the central nervous system (CNS) still holds true, the role of the immune system in the CNS has been revisited over the recent years. This redefining of immune privilege in the brain is a result of the recent re-discovery of the extensive CNS meningeal lymphatic system and the identification of resident T cells in the brain, meningeal layers, and its surrounding cerebrospinal fluid (CSF) in both humans and rodents. While neuro-immune interactions have been classically studied in the context of neuroinflammatory disease, recent works have also elucidated unconventional roles of immune-derived cytokines in neurological function, highlighting the many implications and potential of neuro-immune interactions. As a result, the study of neuro-immune interactions is becoming increasingly important in understanding both CNS homeostasis and disease. Here, we review the anatomically distinct immune compartments within the brain, the known mechanisms of leukocyte trafficking and infiltration into the CNS and unique transcriptional and functional characteristics of CNS-resident immune cells.

Immune checkpoint blockade has demonstrated success in treating cancer but can lead to immune-related adverse events (irAEs), illustrating the centrality of these pathways in tolerance. Here, we describe programmed cell death protein 1 (PD-1) control of T cell responses, focusing on its unique restraint of regulatory T cell function. We examine successes and limitations of checkpoint blockade immunotherapy and review clinical and mechanistic features of irAEs. Last, we discuss strategies to modulate PD-1 blockade to enhance antitumor immunity while limiting autoimmunity.

T cell-B cell interaction is the key immune response to protect the host from severe viral infection. However, how T cells support B cells to exert protective humoral immunity in humans is not well understood. Here, we use COVID-19 as a model of acute viral infections and analyze CD4

B cell depletion in patients with relapsing-remitting multiple sclerosis (RRMS) markedly prevents new MRI-detected lesions and disease activity, suggesting the hypothesis that altered B cell function leads to the activation of T cells driving disease pathogenesis. Here, we performed comprehensive analyses of CD40 ligand- (CD40L-) and IL-21-stimulated memory B cells from patients with MS and healthy age-matched controls, modeling the help of follicular helper T cells (Tfh cells), and found a differential gene expression signature in multiple B cell pathways. Most striking was the impaired TIGIT expression on MS-derived B cells mediated by dysregulation of the transcription factor TCF4. Activated circulating Tfh cells (cTfh cells) expressed CD155, the ligand of TIGIT, and TIGIT on B cells revealed their capacity to suppress the proliferation of IL-17-producing cTfh cells via the TIGIT/CD155 axis. Finally, CCR6+ cTfh cells were significantly increased in patients with MS, and their frequency was inversely correlated with that of TIGIT+ B cells. Together, these data suggest that the dysregulation of negative feedback loops between TIGIT+ memory B cells and cTfh cells in MS drives the activated immune system in this disease.

Patients with radiologically isolated syndrome (RIS) exhibit CNS lesions suggestive of multiple sclerosis (MS) in the absence of overt neurological symptoms characteristic of the disease. They may have concurrent brain atrophy, subtle cognitive impairment, and intrathecal inflammation. At least half ultimately develop MS, cementing RIS as preclinical MS for many. However, high-quality data, including immunologic biomarkers, to guide treatment decisions in this population are lacking. Early intervention with ocrelizumab, a humanized monoclonal antibody approved for relapsing and primary progressive MS that targets CD20The CELLO clinical trial, a phase 4, multicenter, randomized, double-blind, placebo-controlled study conducted as an academic-industry collaboration, aims to (1) assess the efficacy of ocrelizumab in patients with RIS and (2) identify biomarkers indicative of emerging autoimmunity as well as immune recovery after transient B-cell depletion. The study will enroll 100 participants across ≥15 sites. Participants will be aged 18 to 40 years, have RIS (defined as meeting 2017 revised McDonald criteria for dissemination in space), and have either been diagnosed with RIS within the last 5 years or have had new brain lesions identified within 5 years of study entry. A screening program of first-degree relatives of patients with MS will be used to boost recruitment. Eligible patients will be randomized 1:1 to receive 3 courses of ocrelizumab or placebo at baseline, week 24, and week 48. Patients will subsequently be followed up for ≥3 years. The primary outcome is time to development of new radiological or clinical evidence of MS. Secondary and exploratory objectives will investigate neuroimaging, serological and immunologic biomarkers, cognitive function, and patient-reported outcomes. A substudy using single-cell RNA sequencing to characterize blood and CSF immune cells will assess markers associated with conversion to clinical MS.The CELLO study will improve the understanding of B-cell biology in early MS disease pathophysiology, characterize the emergence of CNS autoimmunity, and provide evidence to inform treatment decision-making for individuals with RIS.GOV: NCT04877457.

Single-cell technology can be used to understand the genetic basis of human diseases

Compared with sequencing-based global genomic profiling, cytometry labels targeted surface markers on millions of cells in parallel either by conjugated rare earth metal particles or Unique Molecular Identifier (UMI) barcodes. Correct annotation of these cells to specific cell types is a key step in the analysis of these data. However, there is no computational tool that automatically annotates single cell proteomics data for cell type inference. In this manuscript, we propose an automated single cellproteomics dataannotation approach calledProtAnnoto facilitate cell type assignments without laborious manual gating. ProtAnno is designed to incorporate information from annotated single cell RNA-seq (scRNA-seq), CITE-seq, and prior data knowledge (which can be imprecise) on biomarkers for different cell types. We have performed extensive simulations to demonstrate the accuracy and robustness of ProtAnno. For several single cell proteomics datasets that have been manually labeled, ProtAnno was able to correctly label most single cells. In summary, ProtAnno offers an accurate and robust tool to automate cell type annotations for large single cell proteomics datasets, and the analysis of such annotated cell types can offer valuable biological insights.

Recent work both in vitro and in in vivo animal models has implicated sodium as one of a number of environmental factors in the induction of autoimmune disease, although direct experimental evidence in patients was lacking (1, 2). In PNAS, Huhn et al. (3) find that male patients with multiple sclerosis (MS) and mice with experimental autoimmune encephalitis (EAE) have elevated skin sodium deposition relative to healthy controls, as measured by sodium MRI (23Na-MRI). By quantitatively demonstrating disease-specific elevations in tissue salt stores, they establish the biological relevance of salt as an environmental risk factor for autoimmunity and the utility of 23Na-MRI for studying this phenomenon in vivo. There has been a marked increase in the incidence of autoimmune diseases in the last half-century. While the underlying genetic basis of this class of diseases has recently been elucidated implicating predominantly immune response genes (4, 5), changes in environmental factors must ultimately be driving this increase (Fig. 1). We and others have recently demonstrated that higher but physiologic salt conditions activate the p38/MAPK pathway involving NFAT5 and the serum- and glucocorticoid-inducible kinase 1 (SGK1) during cytokine-induced Th17 polarization (1, 2). Gene silencing or chemical inhibition of p38/MAPK, NFAT5, or SGK1 abrogated the high-salt–induced Th17 cell development. In animal models, high-salt diets caused mice to develop more severe EAE (1, 2) Fig. 1. MS, as with all autoimmune diseases, results from a bad outcome of gene–environmental interactions. Over 233 genetic variants have been identified that interact with environmental triggers including smoking, vitamin D, Epstein–Barr virus, and now as shown here salt that influence immune anatomic niches including the gut, adipose tissue, meninges, and skin that leads to the activation of myelin reactive T cells that initiate MS. It was also … [↵][1]1To whom correspondence may be addressed. Email: david.hafler{at}yale.edu. [1]: #xref-corresp-1-1