Follicular helper T (Tfh) cells provide selection signals to germinal center B cells, which is essential for long-lived antibody responses. High CXCR5 and low CCR7 expression facilitates their homing to B cell follicles and distinguishes them from T helper 1 (Th1), Th2, and Th17 cells. Here, we showed that Bcl-6 directs Tfh cell differentiation: Bcl-6-deficient T cells failed to develop into Tfh cells and could not sustain germinal center responses, whereas forced expression of Bcl-6 in CD4(+) T cells promoted expression of the hallmark Tfh cell molecules CXCR5, CXCR4, and PD-1. Bcl-6 bound to the promoters of the Th1 and Th17 cell transcriptional regulators T-bet and RORgammat and repressed IFN-gamma and IL-17 production. Bcl-6 also repressed expression of many microRNAs (miRNAs) predicted to control the Tfh cell signature, including miR-17-92, which repressed CXCR5 expression. Thus, Bcl-6 positively directs Tfh cell differentiation, through combined repression of miRNAs and transcription factors.

Objective. In the sanroque mouse model of lupus, pathologic germinal centers (GCs) arise due to increased numbers of follicular helper T (Tfh) cells, resulting in high-affinity anti-double-stranded DNA antibodies that cause end-organ inflammation, such as glomerulonephritis. The purpose of this study was to examine the hypothesis that this pathway could account for a subset of patients with systemic lupus erythematosus (SLE).Methods. An expansion of Tfh cells is a causal, and therefore consistent, component of the sanroque mouse phenotype. We validated the enumeration of circulating T cells resembling Tfh cells as a biomarker of this expansion in sanroque mice, and we performed a comprehensive comparison of the surface phenotype of circulating and tonsillar Tfh cells in humans. This circulating biomarker was enumerated in SLE patients (n ‫؍‬ 46), Sjögren's syndrome patients (n ‫؍‬ 17), and healthy controls (n ‫؍‬ 48) and was correlated with disease activity and end-organ involvement.Results. In sanroque mice, circulating Tfh cells increased in proportion to their GC counterparts, making circulating Tfh cells a feasible human biomarker of this novel mechanism of breakdown in GC tolerance. In a subset of SLE patients (14 of 46), but in none of the controls, the levels of circulating Tfh cells (defined as circulating CXCR5؉CD4؉ cells with high expression of Tfh-associated molecules, such as inducible T cell costimulator or programmed death 1) were increased. This cellular phenotype did not vary with time, disease activity, or treatment, but it did correlate with the diversity and titers of autoantibodies and with the severity of end-organ involvement.Conclusion. These findings in SLE patients are consistent with the autoimmune mechanism in sanroque mice and identify Tfh effector molecules as possible therapeutic targets in a recognizable subset of patients with SLE.

Hyper -immunoglobulin E syndrome (HIES) is a primary immune defi ciency characterized by

Engagement of cytokine receptors by specific ligands activate Janus kinase–signal transducer and activator of transcription (STAT) signaling pathways. The exact roles of STATs in human lymphocyte behavior remain incompletely defined. Interleukin (IL)-21 activates STAT1 and STAT3 and has emerged as a potent regulator of B cell differentiation. We have studied patients with inactivating mutations in STAT1 or STAT3 to dissect their contribution to B cell function in vivo and in response to IL-21 in vitro. STAT3 mutations dramatically reduced the number of functional, antigen (Ag)-specific memory B cells and abolished the ability of IL-21 to induce naive B cells to differentiate into plasma cells (PCs). This resulted from impaired activation of the molecular machinery required for PC generation. In contrast, STAT1 deficiency had no effect on memory B cell formation in vivo or IL-21–induced immunoglobulin secretion in vitro. Thus, STAT3 plays a critical role in generating effector B cells from naive precursors in humans. STAT3-activating cytokines such as IL-21 thus underpin Ag-specific humoral immune responses and provide a mechanism for the functional antibody deficit in STAT3-deficient patients.

for the DahLIA Investigators and the Australian and New Zealand Intensive Care Society Clinical Trials Group IMPORTANCE Effective therapy has not been established for patients with agitated delirium receiving mechanical ventilation. OBJECTIVE To determine the effectiveness of dexmedetomidine when added to standard care in patients with agitated delirium receiving mechanical ventilation. DESIGN, SETTING, AND PARTICIPANTS The Dexmedetomidine to Lessen ICU Agitation (DahLIA) study was a double-blind, placebo-controlled, parallel-group randomized clinical trial involving 74 adult patients in whom extubation was considered inappropriate because of the severity of agitation and delirium. The study was conducted at 15 intensive care units in Australia and New Zealand from May 2011 until December 2013. Patients with advanced dementia or traumatic brain injury were excluded. INTERVENTIONS Bedside nursing staff administered dexmedetomidine (or placebo) initially at a rate of 0.5 μg/kg/h and then titrated to rates between 0 and 1.5 μg/kg/h to achieve physician-prescribed sedation goals. The study drug or placebo was continued until no longer required or up to 7 days. All other care was at the discretion of the treating physician. MAIN OUTCOMES AND MEASURES Ventilator-free hours in the 7 days following randomization. There were 21 reported secondary outcomes that were defined a priori. RESULTS Of the 74 randomized patients (median age, 57 years; 18 [24%] women), 2 withdrew consent later and 1 was found to have been randomized incorrectly, leaving 39 patients in the dexmedetomidine group and 32 patients in the placebo group for analysis. Dexmedetomidine increased ventilator-free hours at 7 days compared with placebo (median, 144.8 hours vs 127.5 hours, respectively; median difference between groups, 17.0 hours [95% CI, 4.0 to 33.2 hours]; P = .01). Among the 21 a priori secondary outcomes, none were significantly worse with dexmedetomidine, and several showed statistically significant benefit, including reduced time to extubation (median, 21.9 hours vs 44.3 hours with placebo; median difference between groups, 19.5 hours [95% CI, 5.3 to 31.1 hours]; P < .001) and accelerated resolution of delirium (median, 23.3 hours vs 40.0 hours; median difference between groups, 16.0 hours [95% CI, 3.0 to 28.0 hours]; P = .01). Using hierarchical Cox modeling to adjust for imbalanced baseline characteristics, allocation to dexmedetomidine was significantly associated with earlier extubation (hazard ratio, 0.47 [95% CI, 0.27-0.82]; P = .007). CONCLUSIONS AND RELEVANCE Among patients with agitated delirium receiving mechanical ventilation in the intensive care unit, the addition of dexmedetomidine to standard care compared with standard care alone (placebo) resulted in more ventilator-free hours at 7 days. The findings support the use of dexmedetomidine in patients such as these.