Mouse Natural Killer (NK) Cells Express the Nerve Growth Factor Receptor TrkA, which Is Dynamically Regulated

Background: Nerve growth factor (NGF) is a neurotrophin crucial for the development and survival of neurons. It also acts on cells of the immune system which express the NGF receptors TrkA and p75 NTR and can be produced by them. However, mouse NK cells have not yet been studied in this context. Methodology/Principal Findings: We used cell culture, flow cytometry, confocal microscopy and ELISA assays to investigate the expression of NGF receptors by NK cells and their secretion of NGF. We show that resting NK cells express TrkA and that the expression is different on NK cell subpopulations defined by the relative presence of CD27 and CD11b. Expression of TrkA is dramatically increased in IL-2-activated NK cells. The p75 NTR is expressed only on a very low percentage of NK cells. Functionally, NGF moderately inhibits NK cell degranulation, but does not influence proliferation or cytokine production. NK cells do not produce NGF. Conclusions/Significance: We demonstrate for the first time that mouse NK cells express the NGF receptor TrkA and tha

PI3Kγ is a molecular switch that controls immune suppression

Macrophages play critical, but opposite, roles in acute and chronic inflammation and cancer1,2,3,4,5. In response to pathogens or injury, inflammatory macrophages express cytokines that stimulate cytotoxic T cells, whereas macrophages in neoplastic and parasitic diseases express anti-inflammatory cytokines that induce immune suppression and may promote resistance to T cell checkpoint inhibitors1,2,3,4,5,6,7. Here we show that macrophage PI 3-kinase γ controls a critical switch between immune stimulation and suppression during inflammation and cancer. PI3Kγ signalling through Akt and mTor inhibits NFκB activation while stimulating C/EBPβ activation, thereby inducing a transcriptional program that promotes immune suppression during inflammation and tumour growth. By contrast, selective inactivation of macrophage PI3Kγ stimulates and prolongs NFκB activation and inhibits C/EBPβ activation, thus promoting an immunostimulatory transcriptional program that restores CD8+ T cell activation and cytotoxicity. PI3Kγ synergizes with checkpoint inhibitor therapy to promote tumour regression and increased survival in mouse models of cancer. In addition, PI3Kγ-directed, anti-inflammatory gene expression can predict survival probability in cancer patients. Our work thus demonstrates that therapeutic targeting of intracellular signalling pathways that regulate the switch between macrophage polarization states can control immune suppression in cancer and other disorders

Effect of diesel on chemokines and chemokine receptors involved in helper T cell type 1/type 2 recruitment in patients with asthma.

The objective of this study was to evaluate if diesel exhausts could favor helper T cell type (Th) 2-associated allergic reactions either through an increased production of Th2-associated chemokines and of their associated receptors or through a decrease of Th1-attracting chemokines and chemokine receptors. Diesel but not allergen exposure of peripheral blood mononuclear cells from subjects with allergy induced a release of I-309, whereas both diesel and Der p 1 induced an early but transient release of monokine induced by IFN-gamma and a late release of pulmonary and activation-regulated chemokine. Although both Th1- and Th2-attracting chemokines were induced, the resulting effect was an increased chemotactic activity on Th2 but not Th1 cells. Surprisingly, diesel induced a late increase in the expression of the Th1-associated CXC receptor 3 and CC receptor 5. T cell CXC receptor 3 upregulation was not associated with an increased migration to its ligands. These two antagonistic effects have been previously reported as a scavenger mechanism to clear chemokines. Altogether, these results suggest that diesel, even without allergen, may amplify a type 2 immune response but that it can also increase late Th1-associated chemokine receptor expression, perhaps as a scavenger mechanism to clear pro-Th1 chemokines and promote the Th2 pathway.In VitroJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Low expression of the pan neurotrophin receptor p75^NTR on fresh and activated mouse NK cells.

<p>Splenocytes were stained with anti-NK1.1, anti-CD3 and anti-p75^NTR Ab or isotype control as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015053#s2" target="_blank">Materials and Methods</a>, and analyzed by flow cytometry. Dead cells were excluded by staining with Live Dead cell marker. A gate was set on NK cells (CD3-NK1.1+). Only a weak expression of p75^NTR (grey lines) relative to isotype control (dashed lines) was observed at day 0 (left panel) and after 5 days of culture in the presence of IL-2 (right panel). Data shown are from one representative experiment out of three performed.</p

NGF reduces NK cell degranulation but does not influence IFNγ production.

<p>A and B: Fresh splenocytes were assessed for degranulation (A), reflected by the percentage of CD107a+ NK cells (CD3-NK1.1+), and for cytokine production (B), reflected by the percentage of IFNγ+ NK cells (CD3-NK1.1+). C and D: the same experiment was performed on NK cells (CD3-NK1.1+) cultured for three days in the presence of IL-2 alone (open histograms) or of IL-2+ NGF (100 ng/ml, filled histograms). The white bars correspond to cells cultured during three days with IL-2 alone, and the grey bars correspond to cells cultured with IL-2+ NGF during the same period. On day three, cells from both culture conditions were incubated during five hours in the different conditions shown on the X-axis. Dead cells were excluded by staining with Live Dead cell marker. NGF inhibits degranulation to a certain extent in the condition IL-2+ IL-12+ IL-18+ NGF. The data shown are the means ± SEM of three experiments.</p

TrkA expression on NK cells as assessed by confocal microscopy.

<p>Cells were prepared for confocal microscopy as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015053#s2" target="_blank">Materials and Methods</a>. TrkA, but not p75^NTR, is expressed by activated NK cells (green staining). On fresh NK cells (NK Day 0), the expression level of TrkA is probably too low to be evidenced by confocal microscopy, in contrast to flow cytometry. PC12 is a rat pheochromocytoma cell line that serves as positive control, as it expresses both TrkA and p75^NTR at high levels. The bar corresponds to 3 µm. Data shown are from one representative experiment out of three performed.</p

NGF does not influence NK cell proliferation.

<p>CFSE-stained splenocytes were cultured for three days in the presence of IL-2 and NGF at various concentrations; A: 0 pM (0 ng/ml), B: 0.1 pM (0.001 ng/ml), C: 1 pM, D: 3 pM, E: 10 pM (0.1 ng/ml), F: 10⁴ pM (100 ng/ml). Then NK cells (CD3-NK1.1+) were analysed by flow cytometry. Every peak of CFSE fluorescence corresponds to one generation of cells. Data shown are from one representative experiment out of three performed.</p

Expression of TrkA on NK cells is different depending on the organs and the NK cell subpopulation.

<p>A: NK cells (CD3-NK1.1+) from spleen, lung, bone marrow and peripheral blood were stained with anti-TrkA and anti-p75^NTR Ab and analyzed by flow cytometry. Dead cells were excluded by staining with Live Dead cell marker. The percentage of TrkA+ NK cells is highest in bone marrow and lowest in blood, whereas p75^NTR was expressed only on 3% of NK cells from spleen, lung and bone marrow. B: NK cells (CD3-NK1.1+) from the above mentioned organs were subdivided on the basis of the relative expression of CD27 and CD11b. TrkA expression is lowest on the CD27-CD11b+ population. The data shown are the means ± SEM of three experiments. *: p<0.05.</p