1 2684 151 EVALUATION OF X CHROMOSOME INACTIVATION WITH RESPECT TO HLA GENETIC SUSCEPTIBILITY IN RHEUMATOID ARTHRITIS AND SYSTEMIC SCLEROSIS. BACKGROUND: AUTOIMMUNE DISEASES, INCLUDING RHEUMATOID ARTHRITIS (RA) AND SYSTEMIC SCLEROSIS (SSC) ARE CHARACTERIZED BY A STRONG GENETIC SUSCEPTIBILITY FROM THE HUMAN LEUCOCYTE ANTIGEN (HLA) LOCUS. ADDITIONALLY, DISORDERS OF EPIGENETIC PROCESSES, IN PARTICULAR NON-RANDOM X CHROMOSOME INACTIVATION (XCI), HAVE BEEN REPORTED IN MANY FEMALE-PREDOMINANT AUTOIMMUNE DISEASES. HERE WE TEST THE HYPOTHESIS THAT WOMEN WITH RA OR SSC WHO ARE STRONGLY GENETICALLY PREDISPOSED ARE LESS SUSCEPTIBLE TO XCI BIAS. METHODS: USING METHYLATION SENSITIVE GENOTYPING OF THE ANDROGEN RECEPTOR (AR) GENE, XCI PROFILES WERE PERFORMED IN PERIPHERAL BLOOD MONONUCLEAR CELLS FROM 161 WOMEN WITH RA, 96 WOMEN WITH SSC AND 100 HEALTHY WOMEN. HLA-DRB1 AND DQB1 WERE GENOTYPED. PRESENCE OF SPECIFIC AUTOANTIBODIES WAS DOCUMENTED FOR PATIENTS. XCI SKEWING WAS DEFINED AS HAVING A RATIO >/= 80:20 OF CELLS INACTIVATING THE SAME X CHROMOSOME. RESULTS: 110 WOMEN WITH RA, 68 WOMEN WITH SSC, AND 69 CONTROLS WERE INFORMATIVE FOR THE AR POLYMORPHISM. AMONG THEM 40.9% OF RA PATIENTS AND 36.8% OF SSC PATIENTS HAD SKEWED XCI COMPARED TO 17.4% OF HEALTHY WOMEN (P = 0.002 AND 0.018, RESPECTIVELY). PRESENCE OF RA-SUSCEPTIBILITY ALLELES CODING FOR THE "SHARED EPITOPE" CORRELATED WITH HIGHER SKEWING AMONG RA PATIENTS (P = 0.002) AND SUCH CORRELATION WAS NOT OBSERVED IN OTHER WOMEN, HEALTHY OR WITH SSC. PRESENCE OF SSC-SUSCEPTIBILITY ALLELES DID NOT CORRELATE WITH XCI PATTERNS AMONG SSC PATIENTS. CONCLUSION: DATA DEMONSTRATE XCI SKEWING IN BOTH RA AND SSC COMPARED TO HEALTHY WOMEN. UNEXPECTEDLY, SKEWED XCI OCCURS MORE OFTEN IN WOMEN WITH RA CARRYING THE SHARED EPITOPE, WHICH USUALLY REFLECTS SEVERE DISEASE. THIS REINFORCES THE VIEW THAT LOSS OF MOSAICISM IN PERIPHERAL BLOOD MAY BE A CONSEQUENCE OF CHRONIC AUTOIMMUNITY. 2016 2 31 26 A CASE OF INFECTION-ASSOCIATED ANTIPROTEINASE-3-NEGATIVE CYTOPLASMIC ANTINEUTROPHIL CYTOPLASMIC ANTIBODY PAUCI-IMMUNE FOCAL NECROTIZING GLOMERULONEPHRITIS. WE PRESENT THE CASE OF A MAN WITH GRAM-NEGATIVE SEPSIS AND EXPOSURE TO ORAL SILICA WHO DEVELOPED PAUCI-IMMUNE FOCAL NECROTIZING GLOMERULONEPHRITIS (PI-FNGN) IN THE SETTING OF A SUBACUTE POLYMICROBIAL CENTRAL VENOUS LINE (CVL) INFECTION. HE DEVELOPED A CYTOPLASMIC ANTINEUTROPHIL CYTOPLASMIC AUTOANTIBODY (C-ANCA) THAT WAS ANTIPROTEINASE-3 (PR-3) AND ANTIMYELOPEROXIDASE (MPO) ANTIBODY NEGATIVE. WE BELIEVE THIS IS THE FIRST REPORTED CASE OF GRAM-NEGATIVE SEPSIS-ASSOCIATED PI-FNGN. CHRONIC SILICA EXPOSURE IS A LEADING ENVIRONMENTAL RISK FACTOR IN THE DEVELOPMENT OF ANCA VASCULITIS. ORAL SILICA IS A COMMON PHARMACEUTICAL ADDITIVE AND ITS BIOAVAILABILITY IS BEING RECOGNIZED. ORAL SILICA, THEREFORE, MAY ALSO BE A RISK FOR DEVELOPMENT OF AUTOREACTIVITY. THE PI-FNGN RESOLVED WITH ANTIBIOTIC THERAPY ALONE. THE C-ANCA TITER DECLINED AS THE PI-FNGN RESOLVED. THE CASE SUPPORTS EXPERIMENTAL AND OBSERVATIONAL RESEARCH THAT ENVIRONMENTAL EXPOSURES ACT AS ADJUVANTS FOR AN IMMUNE RESPONSE AND ALSO PROVIDE EPIGENETIC TRIGGERS FOR AUTOREACTIVITY. THE C-ANCA WAS NEGATIVE FOR PR-3, ITS MAJOR ANTIGEN. C-ANCA ANTIGEN SPECIFICITY MAY DEPEND ON THE PATHOGENESIS OF THE UNDERLYING DISEASE, POTENTIALLY ELICITED BY A CROSS-REACTION OF AN ANTIBODY TO FOREIGN AND SELF TARGET ANTIGEN SEQUENCE HOMOLOGY OR ALTERNATIVELY ELICITED BY ANTIGENIC EPITOPE SPREAD. 2010 3 1319 28 DEMETHYLATION OF THE PD-1 PROMOTER IS IMPRINTED DURING THE EFFECTOR PHASE OF CD8 T CELL EXHAUSTION. PD-1 IS AN INHIBITORY RECEPTOR THAT HAS A MAJOR ROLE IN T CELL DYSFUNCTION DURING CHRONIC INFECTIONS AND CANCER. WHILE DEMETHYLATION OF THE PD-1 PROMOTER DNA IS OBSERVED IN EXHAUSTED T CELLS ISOLATED FROM CHRONICALLY INFECTED INDIVIDUALS, LITTLE IS KNOWN ABOUT WHEN THIS STABLE DEMETHYLATION OF PD-1 PROMOTER DNA IS PROGRAMMED DURING THE COURSE OF A CHRONIC INFECTION. TO ASSESS IF PD-1 PROMOTER DNA DEMETHYLATION IS IMPACTED BY PROLONGED STIMULATION DURING EFFECTOR PHASE OF CHRONIC INFECTION, WE ADOPTIVELY TRANSFERRED VIRUS-SPECIFIC DAY 8 EFFECTOR CD8 T CELLS FROM MICE INFECTED WITH LYMPHOCYTIC CHORIOMENINGITIS VIRUS (LCMV) CLONE 13 INTO RECIPIENT MICE THAT HAD CLEARED AN ACUTE INFECTION. WE OBSERVED THAT LCMV-SPECIFIC CD8 T CELLS FROM CHRONICALLY INFECTED MICE MAINTAINED THEIR SURFACE EXPRESSION OF PD-1 EVEN AFTER TRANSFER INTO ACUTE IMMUNE MICE UNTIL DAY 45 POSTTRANSFER. INTERESTINGLY, THE PD-1 TRANSCRIPTIONAL REGULATORY REGION CONTINUED TO REMAIN UNMETHYLATED IN THESE DONOR CD8 T CELLS GENERATED FROM A CHRONIC INFECTION. THE OBSERVED MAINTENANCE OF PD-1 SURFACE EXPRESSION AND THE DEMETHYLATED PD-1 PROMOTER WERE NOT A RESULT OF RESIDUAL ANTIGEN IN THE RECIPIENT MICE, BECAUSE SIMILAR RESULTS WERE SEEN WHEN CHRONIC INFECTION-INDUCED EFFECTOR CELLS WERE TRANSFERRED INTO MICE INFECTED WITH A VARIANT STRAIN OF LCMV (LCMV V35A) BEARING A MUTATION IN THE COGNATE MAJOR HISTOCOMPATIBILITY COMPLEX CLASS I (MHC-I) EPITOPE THAT IS RECOGNIZED BY THE DONOR CD8 T CELLS. IMPORTANTLY, THE MAINTENANCE OF PD-1 PROMOTER DEMETHYLATION IN MEMORY CD8 T CELLS WAS COUPLED WITH IMPAIRED CLONAL EXPANSION AND HIGHER PD-1 RE-EXPRESSION UPON SECONDARY CHALLENGE. THESE DATA SHOW THAT THE IMPRINTING OF THE EPIGENETIC PROGRAM OF THE INHIBITORY RECEPTOR PD-1 OCCURS DURING THE EFFECTOR PHASE OF CHRONIC VIRAL INFECTION. IMPORTANCE: SINCE PD-1 IS A MAJOR INHIBITORY RECEPTOR REGULATING T CELL DYSFUNCTION DURING CHRONIC VIRAL INFECTION AND CANCERS, A BETTER UNDERSTANDING OF THE MECHANISMS THAT REGULATE PD-1 EXPRESSION IS IMPORTANT. IN THIS WORK, WE DEMONSTRATE THAT THE PD-1 EPIGENETIC PROGRAM IN ANTIGEN-SPECIFIC CD8 T CELLS IS FIXED DURING THE PRIMING PHASE OF CHRONIC INFECTION. 2016 4 2145 21 EPIGENETIC MAINTENANCE OF ACQUIRED GENE EXPRESSION PROGRAMS DURING MEMORY CD8 T CELL HOMEOSTASIS. MEMORY CD8 T CELLS HAVE A UNIQUE ABILITY TO PROVIDE LIFELONG IMMUNITY AGAINST PATHOGENS CONTAINING THEIR COGNATE EPITOPE. BECAUSE OF THEIR ABILITY TO PROVIDE LIFELONG PROTECTION, THE GENERATION OF MEMORY T CELLS IS NOW A MAJOR FOCUS FOR CURRENT VACCINATION OR ADOPTIVE CELL THERAPY APPROACHES TO TREAT CHRONIC VIRAL INFECTIONS AND CANCER. IT IS NOW CLEAR THAT MAINTENANCE OF MEMORY CD8 T CELLS OCCURS THROUGH A PROCESS OF ANTIGEN-INDEPENDENT HOMEOSTATIC PROLIFERATION, WHICH IS REGULATED IN PART BY THE GAMMA CHAIN CYTOKINES IL-7 AND IL-15. HERE, WE WILL DESCRIBE THE ROLE OF THESE CYTOKINES IN THE SURVIVAL AND SELF-RENEWAL OF MEMORY CD8 T CELLS. FURTHER, WE WILL DESCRIBE THE ROLE OF EPIGENETICS IN THE MAINTENANCE OF ACQUIRED FUNCTIONS AMONG MEMORY CD8 T CELLS DURING HOMEOSTATIC PROLIFERATION. 2018 5 295 30 AGING INDUCES B CELL DEFECTS AND DECREASED ANTIBODY RESPONSES TO INFLUENZA INFECTION AND VACCINATION. BACKGROUND: AGING IS CHARACTERIZED BY A PROGRESSIVE DECLINE IN THE CAPACITY OF THE IMMUNE SYSTEM TO FIGHT INFLUENZA VIRUS INFECTION AND TO RESPOND TO VACCINATION. AMONG THE SEVERAL FACTORS INVOLVED, IN ADDITION TO INCREASED FRAILTY AND HIGH-RISK CONDITIONS, THE AGE-ASSOCIATED DECREASE IN CELLULAR AND HUMORAL IMMUNE RESPONSES PLAYS A RELEVANT ROLE. THIS IS IN LARGE PART DUE TO INFLAMMAGING, THE CHRONIC LOW-GRADE INFLAMMATORY STATUS OF THE ELDERLY, ASSOCIATED WITH INTRINSIC INFLAMMATION OF THE IMMUNE CELLS AND DECREASED IMMUNE FUNCTION. RESULTS: AGING IS USUALLY ASSOCIATED WITH REDUCED INFLUENZA VIRUS-SPECIFIC AND INFLUENZA VACCINE-SPECIFIC ANTIBODY RESPONSES BUT SOME ELDERLY INDIVIDUALS WITH HIGHER PRE-EXPOSURE ANTIBODY TITERS, DUE TO A PREVIOUS INFECTION OR VACCINATION, HAVE LESS PROBABILITY TO GET INFECTED. EXAMPLES OF THIS EXCEPTION ARE THE ELDERLY INDIVIDUALS INFECTED DURING THE 2009 PANDEMIC SEASON WHO MADE ANTIBODIES WITH BROADER EPITOPE RECOGNITION AND HIGHER AVIDITY THAN THOSE MADE BY YOUNGER INDIVIDUALS. SEVERAL STUDIES HAVE ALLOWED THE IDENTIFICATION OF B CELL INTRINSIC DEFECTS ACCOUNTING FOR SUB-OPTIMAL ANTIBODY RESPONSES OF ELDERLY INDIVIDUALS. THESE DEFECTS INCLUDE 1) REDUCED CLASS SWITCH RECOMBINATION, RESPONSIBLE FOR THE GENERATION OF A SECONDARY RESPONSE OF CLASS SWITCHED ANTIBODIES, 2) REDUCED DE NOVO SOMATIC HYPERMUTATION OF THE ANTIBODY VARIABLE REGION, 3) REDUCED BINDING AND NEUTRALIZATION CAPACITY, AS WELL AS BINDING SPECIFICITY, OF THE SECRETED ANTIBODIES, 4) INCREASED EPIGENETIC MODIFICATIONS THAT ARE ASSOCIATED WITH LOWER ANTIBODY RESPONSES, 5) INCREASED FREQUENCIES OF INFLAMMATORY B CELL SUBSETS, AND 6) SHORTER TELOMERES. CONCLUSIONS: ALTHOUGH INFLUENZA VACCINATION REPRESENTS THE MOST EFFECTIVE WAY TO PREVENT INFLUENZA INFECTION, VACCINES WITH GREATER IMMUNOGENICITY ARE NEEDED TO IMPROVE THE RESPONSE OF ELDERLY INDIVIDUALS. RECENT ADVANCES IN TECHNOLOGY HAVE MADE POSSIBLE A BROAD APPROACH TO BETTER UNDERSTAND THE AGE-ASSOCIATED CHANGES IN IMMUNE CELLS, NEEDED TO DESIGN TAILORED VACCINES AND EFFECTIVE THERAPEUTIC STRATEGIES THAT WILL BE ABLE TO IMPROVE THE IMMUNE RESPONSE OF VULNERABLE INDIVIDUALS. 2020 6 3223 37 HELICOBACTER PYLORI INFECTION AND AUTOIMMUNE DISEASES; IS THERE AN ASSOCIATION WITH SYSTEMIC LUPUS ERYTHEMATOSUS, RHEUMATOID ARTHRITIS, AUTOIMMUNE ATROPHY GASTRITIS AND AUTOIMMUNE PANCREATITIS? A SYSTEMATIC REVIEW AND META-ANALYSIS STUDY. AUTOIMMUNE DISEASES ARE CONSIDERED AS ONE OF THE MOST IMPORTANT DISORDERS OF THE IMMUNE SYSTEM, IN WHICH THE PROLONGED AND CHRONIC PROCESSES ELIMINATE SELF-TOLERANCE TO THE AUTO-ANTIGENS. THE PREVALENCE OF AUTOIMMUNE DISEASES HAS BEEN INCREASING WORLDWIDE IN THE RECENT YEARS. ACCORDING TO THE LITERATURE, BIOLOGICAL PROCESSES SUCH AS THE HOST GENOME, EPIGENETIC EVENTS, ENVIRONMENTAL CONDITION, DRUG CONSUMPTION, AND INFECTIOUS AGENTS ARE THE MOST IMPORTANT RISK FACTORS THAT MAKE THE HOST SUSCEPTIBLE TO THE DEVELOPMENT OF AUTOIMMUNE DISEASES. IN THE RECENT YEARS, THE ROLE OF HELICOBACTER PYLORI IN THE INDUCTION OF AUTOIMMUNE DISEASES HAS ATTRACTED EXTENSIVE ATTENTION. VIA MOLECULAR MIMICRY, EPITOPE SPREADING, BYSTANDER ACTIVATION, POLYCLONAL ACTIVATION, DYSREGULATION IN IMMUNE RESPONSE, AND HIGHLY IMMUNE-DOMINANT VIRULENCE, SUCH AS CAGA, H. PYLORI CAUSES TISSUE DAMAGE, POLARITY, AND PROLIFERATION OF THE HOST CELLS LEADING TO THE MODULATION OF HOST IMMUNE RESPONSES. MOREOVER, GIVEN THE LARGE POPULATION WORLDWIDE INFECTED WITH H. PYLORI, IT SEEMS LIKELY THAT THE BACTERIUM MAY DEVELOP INTO AUTOIMMUNE DISEASES THROUGH DYSREGULATION OF THE IMMUNE RESPONSE. THE FREQUENCY AND RELATIONSHIP BETWEEN H. PYLORI INFECTION AND SYSTEMIC LUPUS ERYTHEMATOSUS, RHEUMATOID ARTHRITIS, AUTOIMMUNE ATROPHY GASTRITIS, AND AUTOIMMUNE PANCREATITIS WERE EVALUATED USING THE DATA FROM 43 STUDIES INVOLVING 5052 PATIENTS. ACCORDING TO STATISTICAL ANALYSIS IT IS PROBABLE THAT INFECTION WITH MORE VIRULENT STRAINS OF H. PYLORI (SUCH AS H. PYLORI CAGA POSITIVE) CAN INCREASE THE RISK OF AUTOIMMUNE DISEASES. IN ADDITION, IT WAS SHOWN THAT INFECTION WITH H. PYLORI CAN PREVENT THE DEVELOPMENT OF ATROPHIC GASTRITIS BY STIMULATING INFLAMMATION IN THE GASTRIC ANTRUM. HOWEVER, FUTURE STUDIES SHOULD CONFIRM THE VALIDITY OF THIS STUDY. 2021 7 4964 24 PATHOGENETIC AND CLINICAL ASPECTS OF ANTI-NEUTROPHIL CYTOPLASMIC AUTOANTIBODY-ASSOCIATED VASCULITIDES. ANTI-NEUTROPHIL CYTOPLASMIC AUTOANTIBODIES (ANCA) TARGETING PROTEINASE 3 (PR3) AND MYELOPEROXIDASE EXPRESSED BY INNATE IMMUNE CELLS (NEUTROPHILS AND MONOCYTES) ARE SALIENT DIAGNOSTIC AND PATHOGENIC FEATURES OF SMALL VESSEL VASCULITIS, COMPRISING GRANULOMATOSIS WITH POLYANGIITIS (GPA), MICROSCOPIC POLYANGIITIS, AND EOSINOPHILIC GPA. GENETIC STUDIES SUGGEST THAT ANCA-ASSOCIATED VASCULITIDES (AAV) CONSTITUTE SEPARATE DISEASES, WHICH SHARE COMMON IMMUNOLOGICAL AND PATHOLOGICAL FEATURES, BUT ARE OTHERWISE HETEROGENEOUS. THE SUCCESSFUL THERAPEUTIC USE OF ANTI-CD20 ANTIBODIES EMPHASIZES THE PROMINENT ROLE OF ANCA AND POSSIBLY OTHER AUTOANTIBODIES IN THE PATHOGENESIS OF AAV. HOWEVER, TO ELUCIDATE CAUSAL EFFECTS IN AAV, A BETTER UNDERSTANDING OF THE COMPLEX INTERPLAY LEADING TO THE EMERGENCE OF B LYMPHOCYTES THAT PRODUCE PATHOGENIC ANCA REMAINS A CHALLENGE. DIFFERENT SCENARIOS SEEM POSSIBLE; E.G., THE BREAK OF TOLERANCE INDUCED BY A SHIFT FROM NON-PATHOGENIC TOWARD PATHOGENIC AUTOANTIGEN EPITOPES IN INFLAMED TISSUE. THIS REVIEW GIVES A BRIEF OVERVIEW ON CURRENT KNOWLEDGE ABOUT GENETIC AND EPIGENETIC FACTORS, BARRIER DYSFUNCTION AND CHRONIC NON-RESOLVING INFLAMMATION, NECRO-INFLAMMATORY AUTO-AMPLIFICATION OF CELLULAR DEATH AND INFLAMMATION, ALTERED AUTOANTIGEN PRESENTATION, ALTERNATIVE COMPLEMENT PATHWAY ACTIVATION, ALTERATIONS WITHIN PERIPHERAL AND INFLAMED TISSUE-RESIDING T- AND B-CELL POPULATIONS, ECTOPIC LYMPHOID TISSUE NEOFORMATION, THE CHARACTERIZATION OF PR3-SPECIFIC T-CELLS, PROPERTIES OF ANCA, LINKS BETWEEN AUTOIMMUNE DISEASE AND INFECTION-TRIGGERED PATHOLOGY, AND ANIMAL MODELS IN AAV. 2018 8 2421 29 EPIGENETIC SIGNATURE OF PD-1+ TCF1+ CD8 T CELLS THAT ACT AS RESOURCE CELLS DURING CHRONIC VIRAL INFECTION AND RESPOND TO PD-1 BLOCKADE. WE HAVE RECENTLY DEFINED A NOVEL POPULATION OF PD-1 (PROGRAMMED CELL DEATH 1)+ TCF1 (T CELL FACTOR 1)+ VIRUS-SPECIFIC CD8 T CELLS THAT FUNCTION AS RESOURCE CELLS DURING CHRONIC LCMV INFECTION AND PROVIDE THE PROLIFERATIVE BURST SEEN AFTER PD-1 BLOCKADE. SUCH CD8 T CELLS HAVE BEEN FOUND IN OTHER CHRONIC INFECTIONS AND ALSO IN CANCER IN MICE AND HUMANS. THESE CD8 T CELLS EXHIBIT STEM-LIKE PROPERTIES UNDERGOING SELF-RENEWAL AND ALSO DIFFERENTIATING INTO THE TERMINALLY EXHAUSTED CD8 T CELLS. HERE WE COMPARED THE EPIGENETIC SIGNATURE OF STEM-LIKE CD8 T CELLS WITH EXHAUSTED CD8 T CELLS. ATAC-SEQ ANALYSIS SHOWED THAT STEM-LIKE CD8 T CELLS HAD A UNIQUE SIGNATURE IMPLICATING ACTIVITY OF HMG (TCF) AND RHD (NF-KAPPAB) TRANSCRIPTION FACTOR FAMILY MEMBERS IN CONTRAST TO HIGHER ACCESSIBILITY TO ETS AND RUNX MOTIFS IN EXHAUSTED CD8 T CELLS. IN ADDITION, REGULATORY REGIONS OF THE TRANSCRIPTION FACTORS TCF7 AND ID3 WERE MORE ACCESSIBLE IN STEM-LIKE CELLS WHEREAS PRDM1 AND ID2 WERE MORE ACCESSIBLE IN EXHAUSTED CD8 T CELLS. WE ALSO COMPARED THE EPIGENETIC SIGNATURES OF THE 2 CD8 T CELL SUBSETS FROM CHRONICALLY INFECTED MICE WITH EFFECTOR AND MEMORY CD8 T CELLS GENERATED AFTER AN ACUTE LCMV INFECTION. BOTH CD8 T CELL SUBSETS GENERATED DURING CHRONIC INFECTION WERE STRIKINGLY DIFFERENT FROM CD8 T CELL SUBSETS FROM ACUTE INFECTION. INTERESTINGLY, THE STEM-LIKE CD8 T CELL SUBSET FROM CHRONIC INFECTION, DESPITE SHARING KEY FUNCTIONAL PROPERTIES WITH MEMORY CD8 T CELLS, HAD A VERY DISTINCT EPIGENETIC PROGRAM. THESE RESULTS SHOW THAT THE CHRONIC STEM-LIKE CD8 T CELL PROGRAM REPRESENTS A SPECIFIC ADAPTATION OF THE T CELL RESPONSE TO PERSISTENT ANTIGENIC STIMULATION. 2019 9 1262 24 CUTTING EDGE: PROLONGED EXPOSURE TO HIV REINFORCES A POISED EPIGENETIC PROGRAM FOR PD-1 EXPRESSION IN VIRUS-SPECIFIC CD8 T CELLS. AG-SPECIFIC CD8 T CELLS PLAY A CRITICAL ROLE IN CONTROLLING HIV INFECTION BUT EVENTUALLY LOSE ANTIVIRAL FUNCTIONS IN PART BECAUSE OF EXPRESSION AND SIGNALING THROUGH THE INHIBITORY PROGRAMMED DEATH-1 (PD-1) RECEPTOR. TO BETTER UNDERSTAND THE IMPACT OF PROLONGED TCR LIGATION ON REGULATION OF PD-1 EXPRESSION IN HIV-SPECIFIC CD8 T CELLS, WE INVESTIGATED THE CAPACITY OF VIRUS-SPECIFIC CD8 T CELLS TO MODIFY THE PD-1 EPIGENETIC PROGRAM AFTER REDUCTION IN VIRAL LOAD. WE OBSERVED THAT THE TRANSCRIPTIONAL REGULATORY REGION WAS UNMETHYLATED IN THE PD-1(HI) HIV-SPECIFIC CD8 T CELLS, WHEREAS IT REMAINED METHYLATED IN DONOR-MATCHED NAIVE CELLS AT ACUTE AND CHRONIC STAGES OF INFECTION. SURPRISINGLY, THE PD-1 PROMOTER REMAINED UNMETHYLATED IN HIV-SPECIFIC CD8 T CELLS FROM SUBJECTS WITH A VIRAL LOAD CONTROLLED BY ANTIVIRAL THERAPY FOR >2 Y OR FROM ELITE CONTROLLERS. TOGETHER, THESE DATA DEMONSTRATE THAT THE EPIGENETIC PROGRAM AT THE PD-1 LOCUS BECOMES FIXED AFTER PROLONGED EXPOSURE TO HIV VIRUS. 2013 10 4596 24 NATURAL KILLER CELLS IN HUMAN IMMUNODEFICIENCY VIRUS-1 INFECTION: SPOTLIGHT ON THE IMPACT OF HUMAN CYTOMEGALOVIRUS. HUMAN CYTOMEGALOVIRUS (HCMV) HAS BEEN CLOSELY ASSOCIATED WITH THE HUMAN RACE ACROSS EVOLUTIONARY TIME. HCMV CO-INFECTION IS NEARLY UNIVERSAL IN HUMAN IMMUNODEFICIENCY VIRUS-1 (HIV-1)-INFECTED INDIVIDUALS AND REMAINS AN IMPORTANT COFACTOR IN HIV-1 DISEASE PROGRESSION EVEN IN THE ERA OF EFFECTIVE ANTIRETROVIRAL TREATMENT. HCMV INFECTION HAS BEEN SHOWN TO HAVE A BROAD AND POTENT INFLUENCE ON THE HUMAN IMMUNE SYSTEM AND HAS BEEN LINKED WITH THE DISCOVERY AND CHARACTERIZATION OF ADAPTIVE NATURAL KILLER (NK) CELLS. DISTINCT NK-CELL SUBSETS, PREDOMINATELY EXPRESSING THE ACTIVATING RECEPTOR NKG2C AND THE MARKER OF TERMINAL DIFFERENTIATION CD57, EXPAND IN RESPONSE TO HCMV. THESE NK-CELL POPULATIONS ENGAGED IN THE LONG-LASTING INTERACTION WITH HCMV, IN ADDITION TO CHARACTERISTIC BUT VARIABLE EXPRESSION OF SURFACE RECEPTORS, EXHIBIT REDUCED EXPRESSION OF SIGNALING PROTEINS AND TRANSCRIPTION FACTORS EXPRESSED BY CANONICAL NK CELLS. BROAD EPIGENETIC MODIFICATIONS DRIVE THE EMERGENCE AND PERSISTENCE OF HCMV-ADAPTED NK CELLS THAT HAVE DISTINCT FUNCTIONAL CHARACTERISTICS. NKG2C(+) NK-CELL EXPANSIONS HAVE BEEN OBSERVED IN HIV-1 INFECTED PATIENTS AND OTHER ACUTE AND CHRONIC VIRAL INFECTIONS BEING SYSTEMATICALLY ASSOCIATED WITH HCMV SEROPOSITIVITY. THE LATTER IS POTENTIALLY AN IMPORTANT CONFOUNDING VARIABLE IN STUDIES FOCUSED ON THE CELLULAR NK-CELL RECEPTOR REPERTOIRE AND FUNCTIONAL CAPACITY. HERE, FOCUSING ON HIV-1 INFECTION WE REVIEW THE EVIDENCE IN FAVOR OF "ADAPTIVE" CHANGES LIKELY INDUCED BY HCMV CO-INFECTION IN NK-CELL SUBSETS. WE HIGHLIGHT A NUMBER OF KEY QUESTIONS AND HOW INSIGHTS INTO THE ADAPTIVE BEHAVIOR OF NK CELLS WILL INFORM NEW STRATEGIES EXPLOITING THEIR UNIQUE PROPERTIES IN THE FIGHT AGAINST HIV-1. 2017 11 4726 16 NOT-SO-OPPOSITE ENDS OF THE SPECTRUM: CD8(+) T CELL DYSFUNCTION ACROSS CHRONIC INFECTION, CANCER AND AUTOIMMUNITY. CD8(+) T CELLS ARE CRITICAL MEDIATORS OF CYTOTOXIC EFFECTOR FUNCTION IN INFECTION, CANCER AND AUTOIMMUNITY. IN CANCER AND CHRONIC VIRAL INFECTION, CD8(+) T CELLS UNDERGO A PROGRESSIVE LOSS OF CYTOKINE PRODUCTION AND CYTOTOXICITY, A STATE TERMED T CELL EXHAUSTION. IN AUTOIMMUNITY, AUTOREACTIVE CD8(+) T CELLS RETAIN THE CAPACITY TO EFFECTIVELY MEDIATE THE DESTRUCTION OF HOST TISSUES. ALTHOUGH THE CLINICAL OUTCOME DIFFERS IN EACH CONTEXT, CD8(+) T CELLS ARE CHRONICALLY EXPOSED TO ANTIGEN IN ALL THREE. THESE CHRONICALLY STIMULATED CD8(+) T CELLS SHARE SOME COMMON PHENOTYPIC FEATURES, AS WELL AS TRANSCRIPTIONAL AND EPIGENETIC PROGRAMMING, ACROSS DISEASE CONTEXTS. A BETTER UNDERSTANDING OF THESE CD8(+) T CELL STATES MAY REVEAL NOVEL STRATEGIES TO AUGMENT CLEARANCE OF CHRONIC VIRAL INFECTION AND CANCER AND TO MITIGATE SELF-REACTIVITY LEADING TO TISSUE DAMAGE IN AUTOIMMUNITY. 2021 12 3861 25 ISOLATION OF HUMAN ANTIGEN-SPECIFIC REGULATORY T CELLS WITH HIGH SUPPRESSIVE FUNCTION. ADOPTIVE TRANSFER OF REGULATORY T (TREG) CELLS COULD BE AN ALTERNATIVE TO CHRONIC IMMUNOSUPPRESSION FOR PREVENTION OF ALLOGENEIC GRAFT REJECTION. WHILE POLYSPECIFIC TREG CELLS CAN PREVENT IMMUNE RESPONSES UNDER LYMPHOPENIC CONDITIONS, AG-SPECIFIC TREG CELLS ARE NEEDED TO TREAT AUTOIMMUNITY AND GRAFT REJECTION. YET, RELIABLE MARKERS FOR AG-SPECIFIC TREG CELLS ARE MISSING. WE REPORT THAT LATENCY-ASSOCIATED PEPTIDE (LAP) AND GLYCOPROTEIN A REPETITIONS PREDOMINANT (GARP) CAN IDENTIFY HUMAN AG-SPECIFIC TREG CELLS. IN ADDITION, WE SHOW THAT THE DEPLETION OF CD154(+) CELLS FROM LAP(+) OR GARP(+) TREG CELLS INCREASES THE TREG-CELL PURITY TO OVER 90%, AS ASSESSED BY EPIGENETIC ANALYSIS. THESE AG-SPECIFIC TREG CELLS CAN BE ISOLATED MAGNETICALLY AND MIGHT CONTRIBUTE TO THE DEVELOPMENT OF GMP-BASED PROTOCOLS. IN ADDITION, AG-SPECIFIC TREG CELLS ARE FUNCTIONALLY FAR SUPERIOR TO CD4(+) CD25(HIGH) OR CD4(+) CD25(HIGH) CD127(LOW) TREG CELLS IN VITRO AND IN PREVENTING STRONG ALLOREACTIONS IN HUMANIZED MICE. THEY COULD, THEREFORE, HAVE A HIGH THERAPEUTIC POTENTIAL FOR THE CONTROL OF ALLOIMMUNE, AUTOIMMUNE, AND ALLERGIC IMMUNE RESPONSES IN PATIENTS. 2014 13 1033 33 CITRULLINATION OF AUTOANTIGENS IMPLICATES NETOSIS IN THE INDUCTION OF AUTOIMMUNITY. TOLERANCE BLOCKS THE EXPRESSION OF AUTOANTIBODIES, WHEREAS AUTOIMMUNITY PROMOTES IT. HOW TOLERANCE BREAKS AND AUTOANTIBODY PRODUCTION BEGINS THUS ARE CRUCIAL QUESTIONS FOR UNDERSTANDING AND TREATMENT OF AUTOIMMUNE DISEASES. EVIDENCE IMPLICATES CELL DEATH AND AUTOANTIGEN MODIFICATIONS IN THE INITIATION OF AUTOIMMUNE REACTIONS. ONE FORM OF NEUTROPHIL CELL DEATH CALLED NETOSIS DESERVES ATTENTION BECAUSE IT REQUIRES THE POST-TRANSLATIONAL MODIFICATION OF HISTONES AND RESULTS IN THE EXTRACELLULAR RELEASE OF CHROMATIN. NETOSIS RECEIVED ITS NAME FROM NET, THE ACRONYM GIVEN TO NEUTROPHIL EXTRACELLULAR TRAP. THE EXTRACELLULAR CHROMATIN INCORPORATES HISTONES IN WHICH ARGININES HAVE BEEN CONVERTED TO CITRULLINES BY PEPTIDYLARGININE DEIMINASE IV (PAD4). THE DEIMINATED CHROMATIN MAY FUNCTION TO CAPTURE OR 'TRAP' BACTERIAL PATHOGENS, THUS GENERATING AN EXTRACELLULAR COMPLEX OF DEIMINATED HISTONES AND BACTERIAL CELL ADJUVANTS. THE COMPLEX OF BACTERIAL ANTIGENS AND DEIMINATED CHROMATIN MAY BE INTERNALISED BY HOST PHAGOCYTES DURING ACUTE INFLAMMATORY CONDITIONS, AS ARISE DURING BACTERIAL INFECTIONS OR CHRONIC AUTOINFLAMMATORY DISORDERS. THE UPTAKE AND PROCESSING OF DEIMINATED CHROMATIN TOGETHER WITH BACTERIAL ADJUVANTS BY PHAGOCYTES MAY INDUCE THE PRESENTATION OF MODIFIED HISTONE EPITOPES AND CO-STIMULATION, THUS YIELDING A POWERFUL STIMULUS TO BREAK TOLERANCE. AUTOANTIBODIES TO DEIMINATED HISTONES ARE PREVALENT IN FELTY'S SYNDROME PATIENTS AND ARE PRESENT IN SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) AND PATIENTS WITH RHEUMATOID ARTHRITIS (RA). THESE OBSERVATIONS CLEARLY IMPLICATE HISTONE DEIMINATION AS AN EPIGENETIC MARK THAT CAN ACT AS AN AUTOANTIBODY STIMULANT. 2014 14 407 30 ANALYSIS OF FOXP3+ REGULATORY T CELLS THAT DISPLAY APPARENT VIRAL ANTIGEN SPECIFICITY DURING CHRONIC HEPATITIS C VIRUS INFECTION. WE REPORTED PREVIOUSLY THAT A PROPORTION OF NATURAL CD25(+) CELLS ISOLATED FROM THE PBMC OF HCV PATIENTS CAN FURTHER UPREGULATE CD25 EXPRESSION IN RESPONSE TO HCV PEPTIDE STIMULATION IN VITRO, AND PROPOSED THAT VIRUS-SPECIFIC REGULATORY T CELLS (TREG) WERE PRIMED AND EXPANDED DURING THE DISEASE. HERE WE DESCRIBE EPIGENETIC ANALYSIS OF THE FOXP3 LOCUS IN HCV-RESPONSIVE NATURAL CD25(+) CELLS AND SHOW THAT THESE CELLS ARE NOT ACTIVATED CONVENTIONAL T CELLS EXPRESSING FOXP3, BUT HARD-WIRED TREG WITH A STABLE FOXP3 PHENOTYPE AND FUNCTION. OF APPROXIMATELY 46,000 GENES ANALYZED IN GENOME WIDE TRANSCRIPTION PROFILING, ABOUT 1% WERE DIFFERENTIALLY EXPRESSED BETWEEN HCV-RESPONSIVE TREG, HCV-NON-RESPONSIVE NATURAL CD25(+) CELLS AND CONVENTIONAL T CELLS. EXPRESSION PROFILES, INCLUDING CELL DEATH, ACTIVATION, PROLIFERATION AND TRANSCRIPTIONAL REGULATION, SUGGEST A SURVIVAL ADVANTAGE OF HCV-RESPONSIVE TREG OVER THE OTHER CELL POPULATIONS. SINCE NO TREG-SPECIFIC ACTIVATION MARKER IS KNOWN, WE TESTED 97 NS3-DERIVED PEPTIDES FOR THEIR ABILITY TO ELICIT CD25 RESPONSE (ASSUMING IT IS A SURROGATE MARKER), ACCOMPANIED BY HIGH RESOLUTION HLA TYPING OF THE PATIENTS. SOME REACTIVE PEPTIDES OVERLAPPED WITH PREVIOUSLY DESCRIBED EFFECTOR T CELL EPITOPES. OUR DATA OFFERS NEW INSIGHTS INTO HCV IMMUNE EVASION AND TOLERANCE, AND HIGHLIGHTS THE NON-SELF SPECIFIC NATURE OF TREG DURING INFECTION. 2009 15 5901 18 T-CELL HETEROGENEITY, PROGENITOR-PROGENY RELATIONSHIPS, AND FUNCTION DURING LATENT AND CHRONIC VIRAL INFECTIONS. UPON RESOLUTION OF AN ACUTE VIRAL INFECTION, DURING LATENT-REACTIVATING INFECTION AND DURING CHRONIC ACTIVE INFECTIONS VIRUS-SPECIFIC T-CELLS DIFFERENTIATE INTO DISTINCT SUBSETS THAT DIFFER IN PHENOTYPE, LONGEVITY, TRANSCRIPTIONAL, METABOLIC, AND EPIGENETIC PROFILES, AND EFFECTOR FUNCTIONS. WITH RECENT ADVANCES IN SINGLE-CELL PROFILING, THIS SUBSTANTIAL HETEROGENEITY HAS BECOME APPARENT AND NEW SUBSETS OF VIRUS-SPECIFIC T CELLS, EITHER OF STABLE OR TRANSITORY NATURE, ARE BEING IDENTIFIED. A UNIFYING PRINCIPLE OF T CELLS EMERGING IN THESE DIFFERENT CONDITIONS IS THEIR PRECURSOR-PROGENY RELATIONSHIP. FOR ACUTE AND RESOLVED VIRAL INFECTIONS, THIS RELATIONSHIP BECOMES APPARENT DURING RE-CHALLENGE, WHEREAS A CONSTANT DIFFERENTIATION OF PROGENITOR T CELLS INTO MORE DIFFERENTIATED CELLS OCCURS DURING LATENT-REACTIVATING AND ACTIVE CHRONIC VIRAL INFECTIONS. IN THIS REVIEW, WE SUMMARIZE AND DISCUSS CURRENT KNOWLEDGE ABOUT T-CELL HETEROGENEITY AND PROGENITOR-PROGENY RELATIONSHIPS IN THE SETTING OF PERSISTENT VIRAL INFECTIONS. 2023 16 1007 23 CHRONIC VIRUS INFECTION ENFORCES DEMETHYLATION OF THE LOCUS THAT ENCODES PD-1 IN ANTIGEN-SPECIFIC CD8(+) T CELLS. FUNCTIONALLY EXHAUSTED T CELLS HAVE HIGH EXPRESSION OF THE PD-1 INHIBITORY RECEPTOR, AND THERAPIES THAT BLOCK PD-1 SIGNALING SHOW PROMISE FOR RESOLVING CHRONIC VIRAL INFECTIONS AND CANCER. BY USING HUMAN AND MURINE SYSTEMS OF ACUTE AND CHRONIC VIRAL INFECTIONS, WE ANALYZED EPIGENETIC REGULATION OF PD-1 EXPRESSION DURING CD8(+) T CELL DIFFERENTIATION. DURING ACUTE INFECTION, NAIVE TO EFFECTOR CD8(+) T CELL DIFFERENTIATION WAS ACCOMPANIED BY A TRANSIENT LOSS OF DNA METHYLATION OF THE PDCD1 LOCUS THAT WAS DIRECTLY COUPLED TO THE DURATION AND STRENGTH OF T CELL RECEPTOR SIGNALING. FURTHER DIFFERENTIATION INTO FUNCTIONAL MEMORY CELLS COINCIDED WITH PDCD1 REMETHYLATION, PROVIDING AN ADAPTED PROGRAM FOR REGULATION OF PD-1 EXPRESSION. IN CONTRAST, THE PDCD1 REGULATORY REGION WAS COMPLETELY DEMETHYLATED IN EXHAUSTED CD8(+) T CELLS AND REMAINED UNMETHYLATED EVEN WHEN VIRUS TITERS DECREASED. THIS LACK OF DNA REMETHYLATION LEAVES THE PDCD1 LOCUS POISED FOR RAPID EXPRESSION, POTENTIALLY PROVIDING A SIGNAL FOR PREMATURE TERMINATION OF ANTIVIRAL FUNCTIONS. 2011 17 3025 37 GENETICS AND PATHOPHYSIOLOGY OF GRANULOMATOSIS WITH POLYANGIITIS (GPA) AND ITS MAIN AUTOANTIGEN PROTEINASE 3. GRANULOMATOSIS WITH POLYANGIITIS (GPA) IS A SEVERE AUTOIMMUNE DISEASE AND ONE OF THE SMALL VESSEL ANTI-NEUTROPHIL CYTOPLASMIC ANTIBODY (ANCA)-ASSOCIATED VASCULITIDES. ALTHOUGH ITS ETIOLOGY AND PATHOPHYSIOLOGY ARE STILL WIDELY UNKNOWN, IT IS ACCEPTED THAT INFECTIONS, ENVIRONMENTAL FACTORS, EPIGENETIC MODIFICATIONS, AND A GENETIC PREDISPOSITION PROVIDE THE BASIS FOR THIS SYSTEMIC DISORDER. GPA TYPICALLY EVOLVES INTO TWO PHASES: AN INITIAL PHASE CHARACTERIZED BY EAR, NOSE AND THROAT (ENT) MANIFESTATIONS, SUCH AS CHRONIC SINUSITIS AND OTITIS, ULCERATION OF THE ORAL CAVITY AND PHARYNX, AS WELL AS PULMONARY NODULES AND A SEVERE GENERALIZED PHASE, DEFINED BY THE OCCURRENCE OF RAPIDLY PROGRESSIVE GLOMERULONEPHRITIS, PULMONARY HEMORRHAGE, AND ARTHRITIS. ANCAS, DIRECTED AGAINST THE NEUTROPHILIC ENZYMES PROTEINASE 3 AND MYELOPEROXIDASE, ARE PRESENT IN UP TO 90% OF THE AFFECTED PATIENTS IN THE SYSTEMIC PHASE. AS THE HUMORAL IMMUNITY IS PREDOMINANTLY DIRECTED AGAINST NEUTROPHILIC ANTIGENS, IT IS APPARENT THAT NEUTROPHILS PLAY A CRITICAL ROLE IN GPA BOTH AS TARGET AND EFFECTOR CELLS. ALTHOUGH GPA PATHOGENESIS IS NOT WELL KNOWN, SOME SUSCEPTIBILITY GENES AND LOCI HAVE BEEN IDENTIFIED BY CANDIDATE GENE APPROACHES, GENOME-WIDE ASSOCIATION STUDIES, AND META-ANALYSES, AS WELL AS FAMILIAL ASSOCIATION STUDIES. SUCH GENES ARE CTLA4, PTPN22, COL11A2, SERPINA1, AND THE MHC CLASS II GENE CLUSTER. THIS REVIEW HIGHLIGHTS THE CLINICAL, PATHOPHYSIOLOGICAL, AND GENETIC BACKGROUND OF GPA AND AIMS TO GIVE AN OVERVIEW OF RECENT EFFORTS TO IDENTIFY GPA SUSCEPTIBILITY GENES. WE POINT OUT THE GENETIC BASIS OF THE MAIN AUTOANTIGEN PR3 AND WHY IT IS SO DIFFICULT TO ESTABLISH A MURINE GPA MODEL. 2016 18 991 26 CHRONIC STIMULATION DRIVES HUMAN NK CELL DYSFUNCTION AND EPIGENETIC REPROGRAMING. A POPULATION OF NATURAL KILLER (NK) CELLS EXPRESSING THE ACTIVATING RECEPTOR NKG2C AND THE MATURATION MARKER CD57 EXPANDS IN RESPONSE TO HUMAN CYTOMEGALOVIRUS (HCMV) INFECTION. CD3-CD56DIMCD57+NKG2C+ NK CELLS ARE SIMILAR TO CD8+ MEMORY T CELLS WITH RAPID AND ROBUST EFFECTOR FUNCTION UPON RE-STIMULATION, PERSISTENCE, AND EPIGENETIC REMODELING OF THE IFNG LOCUS. CHRONIC ANTIGEN STIMULATION DRIVES CD8+ MEMORY T CELL PROLIFERATION WHILE ALSO INDUCING GENOME-WIDE EPIGENETIC REPROGRAMING AND DYSFUNCTION. WE HYPOTHESIZED THAT CHRONIC STIMULATION COULD SIMILARLY INDUCE EPIGENETIC REPROGRAMING AND DYSFUNCTION IN NK CELLS. HERE WE SHOW THAT CHRONIC STIMULATION OF ADAPTIVE NK CELLS THROUGH NKG2C USING PLATE-BOUND AGONISTIC ANTIBODIES IN COMBINATION WITH IL-15 DROVE ROBUST PROLIFERATION AND ACTIVATION OF CD3-CD56DIMCD57+NKG2C+ NK CELLS WHILE SIMULTANEOUSLY INDUCING HIGH EXPRESSION OF THE CHECKPOINT INHIBITORY RECEPTORS LAG-3 AND PD-1. MARKED INDUCTION OF CHECKPOINT INHIBITORY RECEPTORS WAS ALSO OBSERVED ON THE SURFACE OF ADAPTIVE NK CELLS CO-CULTURED WITH HCMV-INFECTED ENDOTHELIAL CELLS. CHRONICALLY STIMULATED ADAPTIVE NK CELLS WERE DYSFUNCTIONAL WHEN CHALLENGED WITH TUMOR TARGETS. THESE CELLS EXHIBITED A PATTERN OF EPIGENETIC REPROGRAMING, WITH GENOME-WIDE ALTERATIONS IN DNA METHYLATION. OUR STUDY HAS IMPORTANT IMPLICATIONS FOR CANCER IMMUNOTHERAPY AND SUGGEST THAT EXHAUSTED NK CELLS COULD BE TARGETED WITH INHIBITORY CHECKPOINT RECEPTOR BLOCKADE. 2019 19 1306 22 DEFINING 'T CELL EXHAUSTION'. 'T CELL EXHAUSTION' IS A BROAD TERM THAT HAS BEEN USED TO DESCRIBE THE RESPONSE OF T CELLS TO CHRONIC ANTIGEN STIMULATION, FIRST IN THE SETTING OF CHRONIC VIRAL INFECTION BUT MORE RECENTLY IN RESPONSE TO TUMOURS. UNDERSTANDING THE FEATURES OF AND PATHWAYS TO EXHAUSTION HAS CRUCIAL IMPLICATIONS FOR THE SUCCESS OF CHECKPOINT BLOCKADE AND ADOPTIVE T CELL TRANSFER THERAPIES. IN THIS VIEWPOINT ARTICLE, 18 EXPERTS IN THE FIELD TELL US WHAT EXHAUSTION MEANS TO THEM, RANGING FROM COMPLETE LACK OF EFFECTOR FUNCTION TO ALTERED FUNCTIONALITY TO PREVENT IMMUNOPATHOLOGY, WITH POTENTIAL DIFFERENCES BETWEEN CANCER AND CHRONIC INFECTION. THEIR RESPONSES HIGHLIGHT THE DICHOTOMY BETWEEN TERMINALLY DIFFERENTIATED EXHAUSTED T CELLS THAT ARE TCF1(-) AND THE SELF-RENEWING TCF1(+) POPULATION FROM WHICH THEY DERIVE. THESE TCF1(+) CELLS ARE CONSIDERED BY SOME TO HAVE STEM CELL-LIKE PROPERTIES AKIN TO MEMORY T CELL POPULATIONS, BUT THE DEVELOPMENTAL RELATIONSHIPS ARE UNCLEAR AT PRESENT. RECENT STUDIES HAVE ALSO HIGHLIGHTED AN IMPORTANT ROLE FOR THE TRANSCRIPTIONAL REGULATOR TOX IN DRIVING THE EPIGENETIC ENFORCEMENT OF EXHAUSTION, BUT KEY QUESTIONS REMAIN ABOUT THE POTENTIAL TO REVERSE THE EPIGENETIC PROGRAMME OF EXHAUSTION AND HOW THIS MIGHT AFFECT THE PERSISTENCE OF T CELL POPULATIONS. 2019 20 2146 21 EPIGENETIC MANIPULATION RESTORES FUNCTIONS OF DEFECTIVE CD8(+) T CELLS FROM CHRONIC VIRAL INFECTION. FUNCTIONAL EXHAUSTION OF ANTIGEN-SPECIFIC T CELLS IS A DEFINING CHARACTERISTIC OF MANY CHRONIC INFECTIONS, BUT THE UNDERLYING MECHANISMS OF T CELL DYSFUNCTION ARE NOT WELL UNDERSTOOD. EPIGENETICS PLAYS AN IMPORTANT ROLE IN THE CONTROL OF T CELL DEVELOPMENT, DIFFERENTIATION, AND FUNCTION. TO EXAMINE IF EPIGENETICS ALSO PLAYS A ROLE IN T CELL EXHAUSTION, WE ANALYZED CHROMATIN REMODELING IN CD8(+) T CELLS FROM MICE WITH CHRONIC LYMPHOCYTIC CHORIOMENINGITIS VIRUS INFECTION. WE OBSERVED DOWNREGULATION OF DIACETYLATED HISTONE H3 IN BOTH VIRUS-SPECIFIC AND TOTAL CD8(+) T CELLS, AND FUNCTIONAL DEFECTS NOT ONLY IN VIRUS-SPECIFIC CD8(+) T CELLS BUT ALSO WITHIN THE TOTAL CD8(+) T CELL POPULATION. IN VITRO TREATMENT OF THESE EXHAUSTED CD8(+) T CELLS WITH HISTONE DEACETYLASE INHIBITORS RESTORED DIACETYLATED HISTONE H3 LEVELS, AND IMPROVED THEIR IMMUNE FUNCTIONS. UPON ADOPTIVE TRANSFER, THESE TREATED CD8(+) T CELLS DEVELOPED INTO FUNCTIONAL MEMORY T CELLS IN VIVO THAT ENHANCED PROTECTIVE IMMUNITY. THESE RESULTS DEFINE A ROLE OF EPIGENETICS IN T CELL EXHAUSTION AND SUGGEST EPIGENETIC MANIPULATION AS A NOVEL MOLECULAR THERAPY TO RESTORE IMMUNE FUNCTIONS. 2014