Innate immunity
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Respiratory burst function of neutrophils is thought to play a pivotal role in the development of pathologies such as indirect (extra-pulmonary) acute lung injury (iALI), as well as sepsis. The current study was conducted to determine the effect of an HIV transactivator of transcription (TAT)-fusion protein containing a soluble N-ethylmaleimide-sensitive factor attachment protein receptor domain from synaptosome-associated protein-23 (SNAP-23) on the shock/sepsis- and sepsis-enhanced neutrophil burst capacity using the clinical relevant two-hit iALI mouse model and the classical cecal ligation and puncture (CLP) septic model. TAT-SNAP-23 significantly decreased the blood neutrophil respiratory burst in vitro, and also in vivo in CLP and hemorrhaged mice. ⋯ Consistent with this, treatment of TAT-SNAP-23 significantly reduced the disruption of lung tissue architecture and protein concentration of bronchoalveolar lavage fluid in iALI mice compared with vehicle-treated iALI mice. In addition, although TAT-SNAP-23 did not alter the extent of local cytokine/chemokine expression, the in vitro migration capacity of neutrophils was blunted from septic and hemorrhagic mice. These data support our hypothesis that TAT-SNAP-23 reduces neutrophil dysfunction in iALI and sepsis by inhibiting neutrophil respiratory burst.
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Gamma delta T-cells have been shown to be important in the early immunoinflammatory response to injury, which can be independent of infection. This sterile inflammatory response is believed to be, in part, associated with danger-associated molecular patterns (DAMPs). Mitochondrial DAMPs (MTDs) have been shown to be important in trauma-induced neutrophil activation, but it is unknown whether MTDs activate other innate immune cells, such as γδ T-cells. ⋯ Both the percentage of cells positive for TLRs and the degree of expression increased. MTDs also induced the production of IL-1β, IL-6, IL-10, RANTES, fibroblast growth factor-basic and vascular endothelial growth factor by γδ T-cells. These findings support the concept that the MTDs released after tissue/cellular injury are capable of activating γδ T-cells, thus initiating sterile inflammation, as well as subsequent healing processes.
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Randomized Controlled Trial Clinical Trial
Body mass index is not associated with cytokine induction during experimental human endotoxemia.
A higher body mass index (BMI) appears to be associated with lower mortality in critically ill patients, possibly explained by an altered innate immune response. However, the precise relationship between BMI and the innate immune response in humans in vivo is unknown. We investigated the relationship between BMI and the systemic cytokine response during experimental human endotoxemia. ⋯ No significant correlations were found between BMI and levels of any of the cytokines or body temperature. No relationship between BMI and the cytokine response was found in healthy volunteers subjected to experimental endotoxemia. These data question the relationship between BMI and cytokine responses in critical illness.
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It is now established that IL-17 has a broad pro-inflammatory potential in mammalian host defense, in inflammatory disease and in autoimmunity, whereas little is known about its anti-inflammatory potential and inhibitory feedback mechanisms. Here, we examined whether IL-17A can inhibit the extracellular release of IL-23 protein, the upstream regulator of IL-17A producing lymphocyte subsets, that is released from macrophages during pulmonary inflammation. We characterized the effect of IL-17A on IL-23 release in several models of pulmonary inflammation, evaluated the presence of IL-17 receptor A (RA) and C (RC) on human alveolar macrophages and assessed the role of the Rho family GTPase Rac1 as a mediator of the effect of IL-17A on the release of IL-23 protein. ⋯ We detected IL-17RA and IL-17RC on human alveolar macrophages, and found that in vitro stimulation of these cells with IL-17A protein, after exposure to LPS, decreased IL-23 protein in conditioned medium, but not IL-23 p19 or p40 mRNA. This study indicates that IL-17A can partially inhibit the release of IL-23 protein during pulmonary inflammation, presumably by stimulating the here demonstrated receptor units IL-17RA and IL-17RC on alveolar macrophages. Hypothetically, the demonstrated mechanism may serve as negative feedback to protect from excessive IL-17A signaling and to control antibacterial host defense once it is activated.
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Alterations in innate immunity that predispose to chronic obstructive pulmonary disease (COPD) exacerbations are poorly understood. We examined innate immunity gene expression in peripheral blood polymorphonuclear leukocytes (PMN) and monocytes stimulated by Haemophilus influenzae and Streptococcus pneumoniae. Thirty COPD patients (15 rapid and 15 non-rapid lung function decliners) and 15 smokers without COPD were studied. ⋯ Exposure to bacterial pathogens causes characteristic innate immune responses in peripheral blood monocytes and PMN in COPD. Bacterial exposure significantly alters the expression of TNF-α in COPD patients, although not consistently. There did not appear to be major differences in innate immune responses between rapid and non-rapid decliners.