Tracking the role of Aire in immune tolerance to the eye with a TCR transgenic mouse model.

Roughly one-half of mice with partial defects in two immune tolerance pathways (AireGW/+Lyn-/- mice) spontaneously develop severe damage to their retinas due to T cell reactivity to Aire-regulated interphotoreceptor retinoid-binding protein (IRBP). Single-cell T cell receptor (TCR) sequencing of CD4+ T cells specific for a predominate epitope of IRBP showed a remarkable diversity of autoantigen-specific TCRs with greater clonal expansions in mice with disease. TCR transgenic mice made with an expanded IRBP-specific TCR (P2.U2) of intermediate affinity exhibited strong but incomplete negative selection of thymocytes. This negative selection was absent in IRBP-/- mice and greatly defective in AireGW/+ mice. Most P2.U2+/- mice and all P2.U.2+/-AireGW/+ mice rapidly developed inflammation of the retina and adjacent uvea (uveitis). Aire-dependent IRBP expression in the thymus also promoted Treg differentiation, but the niche for this fate determination was small, suggesting differences in antigen presentation leading to negative selection vs. thymic Treg differentiation and a stronger role for negative selection in preventing autoimmune disease in the retina.

Parasite-induced TH1 cells and intestinal dysbiosis cooperate in IFN-γ-dependent elimination of Paneth cells.

Activation of Toll-like receptors (TLRs) by pathogens triggers cytokine production and T cell activation, immune defense mechanisms that are linked to immunopathology. Here we show that IFN-γ production by CD4(+) T(H)1 cells during mucosal responses to the protozoan parasite Toxoplasma gondii resulted in dysbiosis and the elimination of Paneth cells. Paneth cell death led to loss of antimicrobial peptides and occurred in conjunction with uncontrolled expansion of the Enterobacteriaceae family of Gram-negative bacteria. The expanded intestinal bacteria were required for the parasite-induced intestinal pathology. The investigation of cell type-specific factors regulating T(H)1 polarization during T. gondii infection identified the T cell-intrinsic TLR pathway as a major regulator of IFN-γ production in CD4(+) T cells responsible for Paneth cell death, dysbiosis and intestinal immunopathology.

Expression of A20 by dendritic cells preserves immune homeostasis and prevents colitis and spondyloarthritis.

Dendritic cells (DCs), which are known to support immune activation during infection, may also regulate immune homeostasis in resting animals. Here we show that mice lacking the ubiquitin-editing molecule A20 specifically in DCs spontaneously showed DC activation and population expansion of activated T cells. Analysis of DC-specific epistasis in compound mice lacking both A20 and the signaling adaptor MyD88 specifically in DCs showed that A20 restricted both MyD88-independent signals, which drive activation of DCs and T cells, and MyD88-dependent signals, which drive population expansion of T cells. In addition, mice lacking A20 specifically in DCs spontaneously developed lymphocyte-dependent colitis, seronegative ankylosing arthritis and enthesitis, conditions stereotypical of human inflammatory bowel disease (IBD). Our findings indicate that DCs need A20 to preserve immune quiescence and suggest that A20-dependent DC functions may underlie IBD and IBD-associated arthritides.

Dendritic cell expression of the signaling molecule TRAF6 is critical for gut microbiota-dependent immune tolerance.

The intracellular signaling molecule TRAF6 is critical for Toll-like receptor (TLR)-mediated activation of dendritic cells (DCs). We now report that DC-specific deletion of TRAF6 (TRAF6ΔDC) resulted, unexpectedly, in loss of mucosal tolerance, characterized by spontaneous development of T helper 2 (Th2) cells in the lamina propria and eosinophilic enteritis and fibrosis in the small intestine. Loss of tolerance required the presence of gut commensal microbiota but was independent of DC-expressed MyD88. Further, TRAF6ΔDC mice exhibited decreased regulatory T (Treg) cell numbers in the small intestine and diminished induction of iTreg cells in response to model antigen. Evidence suggested that this defect was associated with diminished DC expression of interleukin-2 (IL-2). Finally, we demonstrate that aberrant Th2 cell-associated responses in TRAF6ΔDC mice could be mitigated via restoration of Treg cell activity. Collectively, our findings reveal a role for TRAF6 in directing DC maintenance of intestinal immune tolerance through balanced induction of Treg versus Th2 cell immunity.

B cell-intrinsic MyD88 signaling prevents the lethal dissemination of commensal bacteria during colonic damage.

The Toll-like receptor adaptor protein MyD88 is essential for the regulation of intestinal homeostasis in mammals. In this study, we determined that Myd88-deficient mice are susceptible to colonic damage that is induced by dextran sulfate sodium (DSS) administration resulting from uncontrolled dissemination of intestinal commensal bacteria. The DSS-induced mortality of Myd88-deficient mice was completely prevented by antibiotic treatment to deplete commensal bacteria. By using cell type-specific Myd88-deficient mice, we established that B cell-intrinsic MyD88 signaling plays a central role in the resistance to DSS-induced colonic damage via the production of IgM and complement-mediated control of intestinal bacteria. Our results indicate that the lack of intact MyD88 signaling in B cells, coupled with impaired epithelial integrity, enables commensal bacteria to function as highly pathogenic organisms, causing rapid host death.

Selective utilization of Toll-like receptor and MyD88 signaling in B cells for enhancement of the antiviral germinal center response.

The contribution of Toll-like receptor (TLR) signaling to T cell-dependent (TD) antibody responses was assessed by using mice lacking the TLR signaling adaptor MyD88 in individual cell types. When a soluble TLR9 ligand was used as adjuvant for a protein antigen, MyD88 was required in dendritic cells but not in B cells to enhance the TD antibody response, regardless of the inherent immunogenicity of the antigen. In contrast, a TLR9 ligand contained within a virus-like particle substantially augmented the TD germinal center IgG antibody response, and this augmentation required B cell MyD88. The ability of B cells to discriminate between antigens based on the physical form of a TLR ligand probably reflects an adaptation to facilitate strong antiviral antibody responses.

Incidence, predictors and impact of stroke on mortality among patients with acute coronary syndromes following percutaneous coronary intervention-Results from the PROMETHEUS registry.

BACKGROUND: Stroke represents a potentially calamitous complication among patients with acute coronary syndrome (ACS) undergoing percutaneous intervention (PCI). Data on the distribution of stroke occurrence post-PCI and its impact on mortality are scarce. OBJECTIVES: We sought to determine the incidence, predictors and impact of stroke on mortality in ACS patients undergoing PCI. METHODS: A total of 19,914 ACS patients underwent PCI in the PROMETHEUS multicenter observational study. We calculated the cumulative stroke incidence at 30 days and 1 year using the Kaplan Meier method. We also compared the distribution of stroke, myocardial infarction (MI), and bleeding across time and evaluated their overlap. Predictors of stroke were identified through multivariable Cox-regression. Stroke, MI, and bleeding were assessed as time-updated covariates to estimate how each impacts subsequent mortality. RESULTS: We found that 244 patients had a stroke within 1 year, a cumulative incidence of 1.5%. Previous cerebrovascular disease was the strongest predictor for post-PCI stroke, followed by ST-elevation MI presentation, hypertension, non-ST-elevation MI presentation, smoking, female sex, and age. Mortality risk was significantly higher among those who had a stroke versus those who did not (adjusted HR 4.84, p < .0001). However, the association attenuated over time with a much larger effect in the first 30 days of its occurrence (adjusted HR 17.7; 95% CI: 12.3-25.4, p < .0001) versus beyond 30 days (adjusted HR 1.22; 95% CI: 0.6-2.46, p = .58). CONCLUSIONS: Stroke occurrence within 1 year was not uncommon for ACS patients undergoing PCI. When compared with MI and bleeding, stroke had a substantial impact on mortality that attenuated rapidly over time.

B Cell-Intrinsic MyD88 Signaling Promotes Initial Cell Proliferation and Differentiation To Enhance the Germinal Center Response to a Virus-like Particle.

Although TLR signaling in B cells has been implicated in the germinal center (GC) responses during viral infections and autoimmune diseases, the underlying mechanism is unclear. Bacterial phage Qß-derived virus-like particle (Qß-VLP) contains TLR ligands, which can enhance Qß-VLP-induced Ab response, including GC response, through TLR/MyD88 signaling in B cells. In this study, by examining Ag-specific B cell response to Qß-VLP, we found that lack of B cell MyD88 from the beginning of the immune response led to a more severe defect in the GC scale than abolishing MyD88 at later time points of the immune response. Consistently, B cell-intrinsic MyD88 signaling significantly enhanced the initial proliferation of Ag-specific B cells, which was accompanied with a dramatic increase of plasma cell generation and induction of Bcl-6+ GC B cell precursors. In addition, B cell-intrinsic MyD88 signaling promoted strong T-bet expression independent of IFN-γ and led to the preferential isotype switching to IgG2a/c. Thus, by promoting the initial Ag-specific B cell proliferation and differentiation, B cell-intrinsic MyD88 signaling enhanced both T-independent and T-dependent Ab responses elicited by Qß-VLP. This finding will provide additional insight into the role of TLR signaling in antiviral immunity, autoimmune diseases, and vaccine design.

The prevalence, predictors and outcomes of guideline-directed medical therapy in patients with acute myocardial infarction undergoing PCI, an analysis from the PROMETHEUS registry.

OBJECTIVES: To investigate the prevalence, predictors and associations between guideline-directed medical therapy (GDMT) and clinical outcomes in acute myocardial infarction (AMI) patients undergoing percutaneous coronary intervention (PCI) from eight academic centers in the United States. BACKGROUND: Evidence for GDMT in patients with AMI comes from randomized controlled trials. The use of GDMT in clinical practice is unknown in this setting. METHODS: PROMETHEUS is a multicenter observational registry comprising 19,914 patients with acute coronary syndrome (ACS) undergoing PCI. Patients with AMI were divided into two groups based on the prescription of GDMT or not (non-GDMT) at discharge. GDMT was defined according to American College of Cardiology/American Heart Association (ACC/AHA) class I recommendations, specifically, dual antiplatelet therapy, statin and beta-blocker for all AMI patients, and additional ACEI/ARB in patients with left ventricular ejection fraction (LVEF) less than 40%, hypertension, diabetes mellitus (DM) or chronic kidney disease (CKD). The primary endpoint was major adverse cardiovascular events (MACE) defined as a composite of all-cause death, MI, stroke or unplanned target vessel revascularization (TVR) at 1 year. RESULTS: Out of 4,834 patients with AMI, 3,356 (69.4%) patients were discharged on GDMT. Patients receiving GDMT were more often younger and male. Compared with non-GDMT patients, GDMT patients had a significantly lower frequency of comorbidities. Predictors of greater GDMT prescription at discharge were ST-segment elevation myocardial infarction (STEMI), and increased body mass index (BMI), whereas hypertension, prior PCI, anemia and CKD were associated with less GDMT prescription. At 1 year, the use of GDMT was associated with a significantly lower incidence of MACE (13.7% vs. 22.5%; adjusted HR 0.68; 95%CI 0.58-0.80; P < 0.001), death (3.7% vs. 9.4%; adjusted HR 0.61; 95%CI 0.46-0.80; P < 0.001), and unplanned TVR (8.4% vs. 11.3%; adjusted HR 0.76; 95%CI 0.61-0.96; P = 0.020). However, there were no significant differences in the incidence of MI (4.3% vs. 7.0%; adjusted HR 0.75; 95%CI 0.56-1.01; P = 0.056), stroke (1.5% vs. 2.0%; adjusted HR 0.79; 95%CI 0.47-1.34; P = 0.384) between the two groups. CONCLUSION: In a contemporary practice setting in the United States, GDMT was utilized in just over two-thirds of AMI patients undergoing PCI. Predictors of GDMT prescription at discharge included STEMI, BMI and absence of hypertension, CKD, anemia or prior PCI. Use of GDMT was associated with significantly lower risk of 1-year MACE and mortality.

Use of prasugrel and clinical outcomes in African-American patients treated with percutaneous coronary intervention for acute coronary syndromes.

OBJECTIVE: To investigate the use of prasugrel after percutaneous coronary intervention (PCI) in African American (AA) patients presenting with acute coronary syndrome (ACS). BACKGROUND: AA patients are at higher risk for adverse cardiovascular outcomes after PCI and may derive greater benefit from the use of potent antiplatelet therapy. METHODS: Using the multicenter PROMETHEUS observational registry of ACS patients treated with PCI, we grouped patients by self-reported AA or other races. Clinical outcomes at 90-day and 1-year included non-fatal myocardial infarction (MI), major adverse cardiac events (composite of death, MI, stroke, or unplanned revascularization) and major bleeding. RESULTS: The study population included 2,125 (11%) AA and 17,707 (89%) non-AA patients. AA patients were younger, more often female (46% vs. 30%) with a higher prevalence of diabetes mellitus, chronic kidney disease, and prior coronary intervention than non-AA patients. Although AA patients more often presented with troponin (+) ACS, prasugrel use was much less common in AA vs. non-AA (11.9% vs. 21.4%, respectively, P = 0.001). In addition, the use of prasugrel increased with the severity of presentation in non-AA but not in AA patients. Multivariable logistic regression showed AA race was an independent predictor of reduced use of prasugrel (0.42 [0.37-0.49], P < 0.0001). AA race was independently associated with a significantly higher risk of MI at 90-days and 1 year after PCI. CONCLUSIONS: Despite higher risk clinical presentation and worse 1-year ischemic outcomes, AA race was an independent predictor of lower prasugrel prescription in a contemporary population of ACS patients undergoing PCI.

Associations between use of prasugrel vs clopidogrel and outcomes by type of acute coronary syndrome: an analysis from the PROMETHEUS registry.

We sought to investigate the utilization of prasugrel and its association with outcomes relative to clopidogrel in three typical subgroups of ACS in a real-world setting. Prasugrel is superior to clopidogrel for reducing risk of ischemic events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI), but is associated with an increased risk of bleeding complications. PROMETHEUS was a retrospective multicenter observational study of 19,913 ACS patients undergoing PCI from 8 centers in the United States between 2010 and 2013. Major adverse cardiovascular events (MACE) were defined as a composite of all-cause mortality, myocardial infarction, stroke or unplanned revascularization. The study cohort included 3285 (16.5%) patients with ST-segment elevation myocardial infarction (STEMI), 5412 (27.2%) patients with NSTEMI and 11,216 (56.3%) patients with unstable angina (UA). The frequency of prasugrel use at discharge was highest in STEMI and lowest in UA patients, 27.3% versus 22.2% versus 18.9% (p < 0.001). Use of prasugrel vs clopidogrel was associated with a lower rate of MACE in STEMI, NSTEMI, or UA at 1 year, but the differences were attenuated for all groups except for patients with UA (adjusted HR 0.81, 95% CI 0.69-0.94, p = 0.006) after propensity adjusted analysis. After adjustment, there was no difference in bleeding risk between prasugrel and clopidogrel for all groups at 1 year. STEMI patients were more likely to receive prasugrel compared to NSTEMI and UA patients. Prasugrel was associated with reduced adverse outcomes compared with clopidogrel in unadjusted analyses, findings that were largely attenuated upon adjustment and suggest preferential use of prasugrel in low vs high risk patients.

MyD88 Shapes Vaccine Immunity by Extrinsically Regulating Survival of CD4+ T Cells during the Contraction Phase.

Soaring rates of systemic fungal infections worldwide underscore the need for vaccine prevention. An understanding of the elements that promote vaccine immunity is essential. We previously reported that Th17 cells are required for vaccine immunity to the systemic dimorphic fungi of North America, and that Card9 and MyD88 signaling are required for the development of protective Th17 cells. Herein, we investigated where, when and how MyD88 regulates T cell development. We uncovered a novel mechanism in which MyD88 extrinsically regulates the survival of activated T cells during the contraction phase and in the absence of inflammation, but is dispensable for the expansion and differentiation of the cells. The poor survival of activated T cells in Myd88-/- mice is linked to increased caspase3-mediated apoptosis, but not to Fas- or Bim-dependent apoptotic pathways, nor to reduced expression of the anti-apoptotic molecules Bcl-2 or Bcl-xL. Moreover, TLR3, 7, and/or 9, but not TLR2 or 4, also were required extrinsically for MyD88-dependent Th17 cell responses and vaccine immunity. Similar MyD88 requirements governed the survival of virus primed T cells. Our data identify unappreciated new requirements for eliciting adaptive immunity and have implications for designing vaccines.

Use of prasugrel vs clopidogrel and outcomes in patients with acute coronary syndrome undergoing percutaneous coronary intervention in contemporary clinical practice: Results from the PROMETHEUS study.

BACKGROUND AND OBJECTIVES: We sought to determine the frequency of use and association between prasugrel and outcomes in acute coronary syndrome patients undergoing percutaneous coronary intervention (PCI) in clinical practice. METHODS: PROMETHEUS was a multicenter observational registry of acute coronary syndrome patients undergoing PCI from 8 centers in the United States that maintained a prospective PCI registry for patient outcomes. The primary end points were major adverse cardiovascular events at 90days, a composite of all-cause death, nonfatal myocardial infarction, stroke, or unplanned revascularization. Major bleeding was defined as any bleeding requiring hospitalization or blood transfusion. Hazard ratios (HRs) were generated using multivariable Cox regression and stratified by the propensity to treat with prasugrel. RESULTS: Of 19,914 patients (mean age 64.4years, 32% female), 4,058 received prasugrel (20%) and 15,856 received clopidogrel (80%). Prasugrel-treated patients were younger with fewer comorbid risk factors compared with their counterparts receiving clopidogrel. At 90days, there was a significant association between prasugrel use and lower major adverse cardiovascular event (5.7% vs 9.6%, HR 0.58, 95% CI 0.50-0.67, P<.0001) and bleeding (1.9% vs 2.9%, HR 0.65, 95% CI 0.51-0.83, P<.001). After propensity stratification, associations were attenuated and no longer significant for either outcome. Results remained consistent using different approaches to adjusting for potential confounders. CONCLUSIONS: In contemporary clinical practice, patients receiving prasugrel tend to have a lower-risk profile compared with those receiving clopidogrel. The lower ischemic and bleeding events associated with prasugrel use were no longer evident after accounting for these baseline differences.

"Dangerous crystals".

Uric acid (UA) crystals are a potent stimulator of inflammation, but how they activate immune cells is not known. In this issue of Immunity, Ng et al. (2008) provide evidence suggesting that UA activates the Syk kinase via membrane cholesterol.

Toll-like receptors activate innate and adaptive immunity by using dendritic cell-intrinsic and -extrinsic mechanisms.

Toll-like receptors (TLRs) play prominent roles in initiating immune responses to infection, but their roles in particular cell types in vivo are not established. Here we report the generation of mice selectively lacking the crucial TLR-signaling adaptor MyD88 in dendritic cells (DCs). In these mice, the early production of inflammatory cytokines, especially IL-12, was substantially reduced after TLR stimulation. Whereas the innate interferon-gamma response of natural killer cells and of natural killer T cells and the Th1 polarization of antigen-specific CD4(+) T cells were severely compromised after treatment with a soluble TLR9 ligand, they were largely intact after administration of an aggregated TLR9 ligand. These results demonstrate that the physical form of a TLR ligand affects which cells can respond to it and that DCs and other innate immune cells can respond via TLRs and collaborate in promoting Th1 adaptive immune responses to an aggregated stimulus.

Sex-related differences in outcomes among men and women under 55 years of age with acute coronary syndrome undergoing percutaneous coronary intervention: Results from the PROMETHEUS study.

BACKGROUND: Young women undergoing percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) experience greater adverse events than men, potentially due to under-treatment. We sought to compare the 1-year outcomes by sex in patients ≤55 years of age from a contemporary PCI cohort. METHODS: PROMETHEUS was a retrospective multicenter observational US study comparing outcomes in clopidogrel and prasugrel treated patients following ACS PCI. MACE was defined as a composite of death, myocardial infarction, stroke or unplanned revascularization. Clinically significant bleeding was defined as bleeding requiring transfusion or hospitalization. Hazard ratios were generated using multivariable Cox proportional hazards regression. RESULTS: The study cohort included 4,851 patients of which 1,162 (24.0%) were women and 3,689 (76.0%) were men. In this cohort, the prevalence of diabetes (41.0 vs. 27.9%) and chronic kidney disease (12.7 vs. 7.2%) was higher among women compared with men. Irrespective of sex, prasugrel was used in less than one-third of patients (31.8% in men vs. 28.1% in women, P = 0.01). Unadjusted, 1-year MACE (21.1% vs. 16.2%, P < 0.001) and bleeding (3.6% vs. 2.2%, P = 0.01) was significantly higher in women compared with men, but these results were no longer significant after adjustment for risk (HR 1.13, 95% CI 0.94-1.36 for MACE and HR 1.31, 95% CI 0.85-2.04 for bleeding). CONCLUSION: Women ≤ 55 years of age undergoing ACS PCI have significantly greater comorbidities than young men. Despite a higher risk clinical phenotype in women, prasugrel use was significantly lower in women than men. Female sex was associated with a significantly higher risk of 1-year MACE and bleeding than male sex, findings that are attributable to baseline differences. © 2016 Wiley Periodicals, Inc.

Toll-like receptor 9 signaling acts on multiple elements of the germinal center to enhance antibody responses.

Recent studies have demonstrated important roles of nucleic acid-sensing Toll-like receptors (TLRs) in promoting protective antibody responses against several viruses. To dissect how recognition of nucleic acids by TLRs enhances germinal center (GC) responses, mice selectively deleted for myeloid differentiation primary-response protein 88 (MyD88) in B cells or dendritic cells (DCs) were immunized with a haptenated protein antigen bound to a TLR9 ligand. TLR9 signaling in DCs led to greater numbers of follicular helper T (TFH) cells and GC B cells, and accelerated production of broad-affinity antihapten IgG. In addition to modulating GC selection by increasing inducible costimulator (ICOS) expression on TFH cells and reducing the number of follicular regulatory T cells, MyD88-dependent signaling in B cells enhanced GC output by augmenting a class switch to IgG2a, affinity maturation, and the memory antibody response. Thus, attachment of a TLR9 ligand to an oligovalent antigen acted on DCs and B cells to coordinate changes in the T-cell compartment and also promoted B cell-intrinsic effects that ultimately programmed a more potent GC response.

APOBEC3 enzymes restrict marginal zone B cells.

In general, a long-lasting immune response to viruses is achieved when they are infectious and replication competent. In the mouse, the neutralizing antibody response to Friend murine leukemia virus is contributed by an allelic form of the enzyme Apobec3 (abbreviated A3). This is counterintuitive because A3 directly controls viremia before the onset of adaptive antiviral immune responses. It suggests that A3 also affects the antibody response directly. Here, we studied the relative size of cell populations of the adaptive immune system as a function of A3 activity. We created a transgenic mouse that expresses all seven human A3 enzymes and compared it to WT and mouse A3-deficient mice. A3 enzymes decreased the number of marginal zone B cells, but not the number of follicular B or T cells. When mouse A3 was knocked out, the retroelement hitchhiker-1 and sialyl transferases encoded by genes close to it were overexpressed three and two orders of magnitude, respectively. We suggest that A3 shifts the balance, from the fast antibody response mediated by marginal zone B cells with little affinity maturation, to a more sustained germinal center B-cell response, which drives affinity maturation and, thereby, a better neutralizing response.

Germinal centers and autoimmune disease in humans and mice.

Antibodies are involved in the pathogenesis of many autoimmune diseases. Although the mechanisms underlying the antibody response to infection or vaccination are reasonably well understood, we still have a poor understanding of the nature of autoimmune antibody responses. The most well studied are the anti-nuclear antibody responses characteristic of systemic lupus erythematosus and studies over the past decade or so have demonstrated a critical role for signaling by TLR7 and/or TLR9 in B cells to promote these responses. These Toll-like receptors (TLRs) can promote T-cell-independent extrafollicular antibody responses with a heavy-chain class switch and a low degree of somatic mutation, but they can also strongly boost the germinal center response that gives rise to high-affinity antibodies and long-lived plasma cells. TLRs have been shown to enhance affinity maturation in germinal center responses to produce high-affinity neutralizing antibodies in several virus infection models of mice. Although more data are needed, it appears that anti-nuclear antibodies in mouse models of lupus and in lupus patients can be generated by either pathway, provided there are genetic susceptibility alleles that compromise B-cell tolerance at one or another stage. Limited data in other autoimmune diseases suggest that the germinal center response may be the predominant pathway leading to autoantibodies in those diseases. A better understanding of the mechanisms of autoantibody production may ultimately be helpful in the development of targeted therapeutics for lupus or other autoimmune diseases.