TH17 cells require ongoing classic IL-6 receptor signaling to retain transcriptional and functional identity

Acting in concert with TGF-b, IL-6 signaling induces Th17 cell development by programming Th17-related genes via STAT3. A role for IL-6 signaling beyond the inductive phase of Th17 cell development has not been defined, as IL-23 signaling downstream of Th17 cell induction also activates STAT3 and is thought responsible for Th17 cell maintenance. Here, we find that IL-6 signaling is required for both induction and maintenance of Th17 cells; IL-6Ra–deficient Th17 cells rapidly lost their Th17 phenotype and did not cause disease in two models of colitis. Cotransfer of WT Th17 cells with IL-6Ra–deficient Th17 cells induced colitis but was unable to rescue phenotype loss of the latter. High IL-6 in the colon promoted classic, or cis, rather than trans receptor signaling that was required for maintenance of Th17 cells. Thus, ongoing classic IL6 signaling underpins the Th17 program and is required for Th17 cell maintenance and function

Implication of major adverse postoperative events and myocardial injury on disability and survival: A planned subanalysis of the ENIGMA-II trial

BACKGROUND: Globally, \u3e300 million patients have surgery annually, and ≤20% experience adverse postoperative events. We studied the impact of both cardiac and noncardiac adverse events on 1-year disability-free survival after noncardiac surgery. METHODS: We used the study cohort from the Evaluation of Nitrous oxide in Gas Mixture of Anesthesia (ENIGMA-II) trial, an international randomized trial of 6992 noncardiac surgical patients. All were ≥45 years of age and had moderate to high cardiac risk. The primary outcome was mortality within 1 postoperative year. We defined 4 separate types of postoperative adverse events. Major adverse cardiac events (MACEs) included myocardial infarction (MI), cardiac arrest, and myocardial revascularization with or without troponin elevation. MI was defined using the third Universal Definition and was blindly adjudicated. A second cohort consisted of patients with isolated troponin increases who did not meet the definition for MI. We also considered a cohort of patients who experienced major adverse postoperative events (MAPEs), including unplanned admission to intensive care, prolonged mechanical ventilation, wound infection, pulmonary embolism, and stroke. From this cohort, we identified a group without troponin elevation and another with troponin elevation that was not judged to be an MI. Multivariable Cox proportional hazard models for death at 1 year and assessments of proportionality of hazard functions were performed and expressed as an adjusted hazard ratio (aHR) and 95% confidence intervals (CIs). RESULTS: MACEs were observed in 469 patients, and another 754 patients had isolated troponin increases. MAPEs were observed in 631 patients. Compared with control patients, patients with a MACE were at increased risk of mortality (aHR, 3.36 [95% CI, 2.55-4.46]), similar to patients who suffered a MAPE without troponin elevation (n = 501) (aHR, 2.98 [95% CI, 2.26-3.92]). Patients who suffered a MAPE with troponin elevation but without MI had the highest risk of death (n = 116) (aHR, 4.29 [95% CI, 2.89-6.36]). These 4 types of adverse events similarly affected 1-year disability-free survival. CONCLUSIONS: MACEs and MAPEs occur at similar frequencies and affect survival to a similar degree. All 3 types of postoperative troponin elevation in this analysis were associated, to varying degrees, with increased risk of death and disability

IL-21 and IL-6 Are Critical for Different Aspects of B Cell Immunity and Redundantly Induce Optimal Follicular Helper CD4 T Cell (Tfh) Differentiation

Cytokines are important modulators of lymphocytes, and both interleukin-21 (IL-21) and IL-6 have proposed roles in T follicular helper (Tfh) differentiation, and directly act on B cells. Here we investigated the absence of IL-6 alone, IL-21 alone, or the combined lack of IL-6 and IL-21 on Tfh differentiation and the development of B cell immunity in vivo. C57BL/6 or IL-21−/− mice were treated with a neutralizing monoclonal antibody against IL-6 throughout the course of an acute viral infection (lymphocytic choriomeningitis virus, LCMV). The combined absence of IL-6 and IL-21 resulted in reduced Tfh differentiation and reduced Bcl6 protein expression. In addition, we observed that these cytokines had a large impact on antigen-specific B cell responses. IL-6 and IL-21 collaborate in the acute T-dependent antiviral antibody response (90% loss of circulating antiviral IgG in the absence of both cytokines). In contrast, we observed reduced germinal center formation only in the absence of IL-21. Absence of IL-6 had no impact on germinal centers, and combined absence of both IL-21 and IL-6 revealed no synergistic effect on germinal center B cell development. Studying CD4 T cells in vitro, we found that high IL-21 production was not associated with high Bcl6 or CXCR5 expression. TCR stimulation of purified naïve CD4 T cells in the presence of IL-6 also did not result in Tfh differentiation, as determined by Bcl6 or CXCR5 protein expression. Cumulatively, our data indicates that optimal Tfh formation requires IL-21 and IL-6, and that cytokines alone are insufficient to drive Tfh differentiation

Factors Guiding Cd4 T Cell Fate Bifurcations

Naïve CD4 T cells differentiate into a variety of phenotypically and functionally distinct subsets uniquely tailored to the specific inflammatory context. Despite the extraordinary heterogeneity of potential fate outcomes, two distinct but related functional bifurcations appear common to all inflammatory contexts. Following activation, CD4 T cells either home to the site of inflammation and influence peripheral events or remain in the secondary lymphoid tissue to modulate central processes. Similarly, activated cells either drive or suppress inflammation. These functional bifurcations are coincident and sufficiently independent to allow for the simultaneous generation of all four potential outcomes. Pro-inflammatory cells retained in the lymphoid tissue develop into T follicular helpers (Tfh), while traditional non-Tfh effector subsets migrate to the periphery. Each exists in mutual opposition to a specific anti-inflammatory counterpart. Induced regulatory T cells (iTreg cells) suppress peripheral inflammation, while T follicular regulatory cells (Tfr) are found in secondary lymphoid tissues. These populations develop in response to all major pathogen types and in the context of autoimmunity, and undergo similar qualitative changes relevant to the specific inflammatory context. Thus, the complexity of CD4 T cell differentiation can be collapsed into discrete binary outcomes along two functional dimensions. Application of this conceptual framework allows for the identification of factors and processes relevant to a broad array of inflammatory contexts and informs experimental design. Intentional isolation of a single functional axis simplifies experimental results into binary outcomes. Thus we have pursued two separate sets of studies, each designed to examine a different functional dimension. In the first set of experiments, we show that differential expression of IL-2 by recently activated naïve cells defines precursors fated for central versus peripheral function, with the Tfh compartment exclusively supplied by former IL-2 producers. The transcriptional bifurcations underlying these fate outcomes occur simultaneously, precede cell division, and are directly linked to TCR signal strength. In the second set of experiments, we address the development of pro-inflammatory and suppressive populations. We show that insulin-like growth factors (Igfs) reciprocally regulate the differentiation of iTreg and Th17 cell populations, biasing both the amplitude and quality of the pro-inflammatory response. Igfs suppress iTreg cell differentiation, augment Th17 cell development, and enhance expression of key effector genes in mature Th17 cells

Emerging Complexity in CD4+T Lineage Programming and Its Implications in Colorectal Cancer

The intestinal immune system has the difficult task of protecting a large environmentally exposed single layer of epithelium from pathogens without allowing inappropriate inflammatory responses. Unmitigated inflammation drives multiple pathologies, including the development of colorectal cancer. CD4+T cells mediate both the suppression and promotion of intestinal inflammation. They comprise an array of phenotypically and functionally distinct subsets tailored to a specific inflammatory context. This diversity of form and function is relevant to a broad array of pathologic and physiologic processes. The heterogeneity underlying both effector and regulatory T helper cell responses to colorectal cancer, and its impact on disease progression, is reviewed herein. Importantly, T cell responses are dynamic; they exhibit both quantitative and qualitative changes as the inflammatory context shifts. Recent evidence outlines the role of CD4+T cells in colorectal cancer responses and suggests possible mechanisms driving qualitative alterations in anti-cancer immune responses. The heterogeneity of T cells in colorectal cancer, as well as the manner and mechanism by which they change, offer an abundance of opportunities for more specific, and likely effective, interventional strategies.</jats:p

Insulin-like growth factors are essential for the differentiation of Th17s in EAE (LYM8P.635)

Abstract Insulin-like growth factors (Igfs) are highly conserved proteins similar to pro-insulin in both sequence and structure. They function primarily by binding the Igf1 receptor (Igf1R) and exert pleiotropic effects on many tissues throughout life. These factors were shown to be essential for the normal development and proliferation of B and T lymphocytes, and to positively influence their proliferation and survival following activation. But early attempts to identify potential roles in T cell differentiation and function lead to conflicting results, and the field was largely abandoned. More recent advances in our understanding of T cell biology, however, including the discovery of Th17 and Treg C4s, have permitted a more sophisticated analysis of the role of this system in T cells. Our data indicate that Th17 and Treg CD4s express Igf1R and insulin-like growth factor binding protein 4 (Igfbp4), a critical regulator of Igf activity, at much higher levels than other CD4 T cells, and appear uniquely capable of responding to Igfs. Exogenous Igfs promote Th17 and suppress Treg differentiation in-vitro, yet fail to influence Th1 or Th2 differentiation. Deletion of Igf1R leads to a defect in Stat3 phosphorylation and IL17a production, and enhanced Treg differentiation in-vitro. Mice lacking Igf1R on T cells are substantially protected from Experimental Autoimmune Encephalomyelitis, an effect that can be recapitulated through the in-vivo administration of Igf1R blocking antibodies.</jats:p

Roles of Bcl6 and Blimp1 in CD4 T follicular helper (Tfh) lineage commitment (99.11)

Abstract A distinct CD4 effector T cell subset, called T follicular helper cells (Tfh), is required for proper B cell responses in vivo. The mutually antagonistic transcription factors Bcl6 and Blimp1 play central but opposing roles in Tfh differentiation (Johnston et al., Science 2009). Bcl6 is both necessary and sufficient for in vivo Tfh differentiation, while Blimp1 specifically inhibits it. Expression of both Bcl6 and Blimp1, controlled temporally and spatially by cell-cell contact and multiple cytokines, is necessary for a normal CD4 T cell response. Naïve CD4 T cells express Bcl6 mRNA prior to, and independent of, commitment to the Tfh lineage. Bcl6 contains multiple functional domains and can affect different transcriptional outcomes depending on the local chromatin and co-repressor environment. Bcl6 repression of Blimp1 requires the co-repressor MTA3, which binds the Bcl6 RDII domain. We show that a loss of function mutation in the Bcl6 RDII domain results in a total failure of CD4 T cells to proliferate in vivo following infection with LCMV. We posit that this proliferation defect is a result of the failure to control expression of Blimp1, a strongly anti-proliferative protein, immediately following activation. Conversely, failure to attain adequate Blimp1 expression also results in an abnormal antiviral CD4 T cell response. Taken together, our findings suggest that the roles of Bcl6 and Blimp1 in CD4 T cells extend beyond Tfh lineage commitment.</jats:p

Hemolysis Index and Potassium Reporting

Abstract Objectives In vitro hemolysis generates a spurious increase in potassium. Roche Diagnostics recently revised its recommended guidelines for potassium reporting on cobas analyzers. By dramatically reducing the allowable degree of hemolysis, these guidelines would increase specimen rejection rates. We attempted to balance the desire to avoid inaccurate results with the clinical implications of increased specimen rejection rates. Methods We downloaded hemolytic indices (HI) for 80,795 specimens tested at our institution on cobas chemistry analyzers in 1 month and evaluated potential specimen rejection rates based on the new criteria. We also spiked nonhemolyzed samples with hemolyzed blood to assess the influence of HI values on potassium measurements. Results The new recommendations would lead to specimen rejection rates of 76% in the neonatal intensive care unit (NICU), 41% in the emergency department (ED), 16% in inpatient specimens, and 9% in outpatient samples. Our current criteria of reporting potassium concentrations in inpatient and outpatient specimens with HI ≤100 and in NICU and ED specimens with HI ≤300 and additional interpretive guidance for HI values between 100 and 300 reduce unnecessary specimen rejections to 3% in NICU, 2% in ED and inpatients, and less than 1% in outpatients without significantly increasing the number of clinically consequential incorrect results. Conclusions The new recommendations would lead to unacceptably high specimen rejection rates. Laboratories should develop context-specific, evidence-based reporting criteria that minimize reporting of inaccurate results without disrupting delivery of care. </jats:sec

Radiation-induced intracranial osteosarcoma of the anterior skull base after treatment of esthesioneuroblastoma

Esthesioneuroblastoma (ENB) is an uncommon sinonasal cancer of the olfactory neuroepithelium that is typically treated with surgical resection followed by radiation therapy. Radiation-induced intracranial osteosarcoma of the skull base is a rare but devastating long-term complication of radiation therapy in this region. Here, we present a case of an 82-year-old patient who developed radiation-induced osteosarcoma of the anterior skull base and paranasal sinuses 10 years after radiation therapy following resection of an ENB. Older patients may be at risk of developing this complication earlier and with a worse prognosis relative to younger patients. Treating physicians/surgeons should be aware of this devastating complication. Patients who are treated with high-dose radiation therapy in this region should be followed for many years.</jats:p