Specialized pro-resolving mediators (SPMs) are enzymatically derived from essential fatty acids and have important roles in orchestrating the resolution of tissue inflammation -that is, catabasis. Host responses to tissue infection elicit acute inflammation in an attempt to control invading pathogens. SPMs are lipid mediators that are part of a larger family of pro-resolving molecules, which includes proteins and gases, that together restrain inflammation and resolve the infection. These immunoresolvents are distinct from immunosuppressive molecules as they not only dampen inflammation but also promote host defence. Here, we focus primarily on SPMs and their roles in lung infection and inflammation to illustrate the potent actions these mediators play in restoring tissue homeostasis after an infection.Acute inflammation is a vital response to infection that is initiated within seconds of pathogen detection 1 . Granulocytes are rapidly recruited to sites of infection 2 , where they become activated and augment the resident capacity of infected tissue to kill and ultimately clear the pathogen 3 . These early events in the host response to infection are essential for survival and are coordinated by several families of pro-inflammatory mediators, including lipid mediators (such as prostaglandins and leukotrienes), cytokines and chemokines. These pro-inflammatory mediators have overlapping and distinct functions and ultimately induce an increase in vascular permeability and orchestrate leukocyte recruitment. This leads to the cardinal signs of tissue inflammation -namely calor, rubor, tumor, dolor and potentially functio laesa (FIG. 1).Recently, a new array of molecules that function in the resolution of inflammation were elucidated and named specialized pro-resolving mediators (SPMs) 4,5 . Many of these SPMs are produced during the acute inflammatory response 6 , and their structure, biosynthesis and organic synthesis have been recently reviewed (see REF. 5). Typically, acute inflammatory responses to pathogens are self-limiting, and there is a growing appreciation that SPMs have pivotal anti-inflammatory and anti-infective roles in tissue catabasis 4 . For effective Correspondence to B.D.L. blevy@partners.org. Competing interests statementThe authors declare competing interests: see Web version for details. DATABASES ClinicalTrials.gov: http://www.clinicaltrials.gov ALL LINKS ARE ACTIVE IN THE ONLINE PDF HHS Public AccessAuthor manuscript Nat Rev Immunol. Author manuscript; available in PMC 2017 January 18. Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript resolution of inflammation to occur in tissues, cessation of granulocyte recruitment is required in conjunction with the recruitment and differentiation of macrophages, which help clear inflammatory cells and tissue debris to restore tissue homeostasis 7 . Granulocytes in the tissue undergo apoptosis during the resolution of inflammation to prevent bystander tissue injury occurring from the release of potentially toxic cellular conten...

This study compared second generation chimeric antigen receptors encoding signaling domains composed of CD28, ICOS and 4-1BB. Here we report that certain CARs endow T cells with the ability to undergo long-term autonomous proliferation. Transduction of primary human T-cell with lentiviral vectors encoding some of the CARs resulted in sustained proliferation for up to three months following a single stimulation through the TCR. Sustained numeric expansion was independent of cognate antigen and did not require the addition of exogenous cytokines or feeder cells after a single stimulation of the TCR and CD28. Results from gene array and functional assays linked sustained cytokine secretion and expression of T-bet, EOMES and GATA-3 to the effect. Sustained expression of the endogenous IL2 locus has not been reported in primary T cells. Sustained proliferation was dependent on CAR structure and high expression, the latter of which was necessary but not sufficient. The mechanism involves constitutive signaling through NF-kB, Akt, Erk and NFAT. The propagated CAR T cells retained a diverse TCR repertoire and cellular transformation was not observed. The CARs with a constitutive growth phenotype displayed inferior antitumor effects and engraftment in vivo. Therefore the design of CARs that have a non-constitutive growth phenotype may be a strategy to improve efficacy and engraftment of CAR T cells. The identification of CARs that confer constitutive or non-constitutive growth patterns may explain observations that CAR T cells have differential survival patterns in clinical trials.

The respiratory system, which includes the trachea, airways, and distal alveoli, is a complex multi-cellular organ that intimately links with the cardiovascular system to accomplish gas exchange. In this review and as members of the NIH/NHLBI-supported Progenitor Cell Translational Consortium, we discuss key aspects of lung repair and regeneration. We focus on the cellular compositions within functional niches, cell-cell signaling in homeostatic health, the responses to injury, and new methods to study lung repair and regeneration. We also provide future directions for an improved understanding of the cell biology of the respiratory system, as well as new therapeutic avenues.

The lung alveolus is the functional unit of the respiratory system required for gas exchange. During the transition to air breathing at birth, biophysical forces are thought to shape the emerging tissue niche. However, the intercellular signaling that drives these processes remains poorly understood. Applying a multimodal approach, we identified alveolar type 1 (AT1) epithelial cells as a distinct signaling hub. Lineage tracing demonstrates that AT1 progenitors align with receptive, force-exerting myofibroblasts in a spatial and temporal manner. Through single-cell chromatin accessibility and pathway expression (SCAPE) analysis, we demonstrate that AT1-restricted ligands are required for myofibroblasts and alveolar formation. These studies show that the alignment of cell fates, mediated by biophysical and AT1-derived paracrine signals, drives the extensive tissue remodeling required for postnatal respiration.

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Alveolar epithelial regeneration is essential for recovery from devastating lung diseases. This process occurs when type II alveolar pneumocytes (AT2 cells) proliferate and transdifferentiate into type I alveolar pneumocytes (AT1 cells). We used genome-wide analysis of chromatin accessibility and gene expression following acute lung injury to elucidate repair mechanisms. AT2 chromatin accessibility changed substantially following injury to reveal STAT3 binding motifs adjacent to genes that regulate essential regenerative pathways. Single-cell transcriptome analysis identified brain-derived neurotrophic factor (Bdnf) as a STAT3 target gene with newly accessible chromatin in a unique population of regenerating AT2 cells. Furthermore, the BDNF receptor tropomyosin receptor kinase B (TrkB) was enriched on mesenchymal alveolar niche cells (MANCs). Loss or blockade of AT2-specific Stat3, Bdnf or mesenchyme-specific TrkB compromised repair and reduced Fgf7 expression by niche cells. A TrkB agonist improved outcomes in vivo following lung injury. These data highlight the biological and therapeutic importance of the STAT3-BDNF-TrkB axis in orchestrating alveolar epithelial regeneration.