Toll-like receptors (TLRs) are the best characterized pattern recognition receptors. Individual TLRs recruit diverse combinations of adaptor proteins, triggering signal transduction pathways and leading to the activation of various transcription factors, including nuclear factor kappaB, activation protein 1 and interferon regulatory factors. Interleukin-2 is one of the molecules produced by mouse dendritic cells after stimulation by different pattern recognition receptor agonists. By analogy with the events after T-cell receptor engagement leading to interleukin-2 production, it is therefore plausible that the stimulation of TLRs on dendritic cells may lead to activation of the Ca(2+)/calcineurin and NFAT (nuclear factor of activated T cells) pathway. Here we show that mouse dendritic cell stimulation with lipopolysaccharide (LPS) induces Src-family kinase and phospholipase Cgamma2 activation, influx of extracellular Ca(2+) and calcineurin-dependent nuclear NFAT translocation. The initiation of this pathway is independent of TLR4 engagement, and dependent exclusively on CD14. We also show that LPS-induced NFAT activation via CD14 is necessary to cause the apoptotic death of terminally differentiated dendritic cells, an event that is essential for maintaining self-tolerance and preventing autoimmunity. Consequently, blocking this pathway in vivo causes prolonged dendritic cell survival and an increase in T-cell priming capability. Our findings reveal novel aspects of molecular signalling triggered by LPS in dendritic cells, and identify a new role for CD14: the regulation of the dendritic cell life cycle through NFAT activation. Given the involvement of CD14 in disease, including sepsis and chronic heart failure, the discovery of signal transduction pathways activated exclusively via CD14 is an important step towards the development of potential treatments involving interference with CD14 functions.

A Numb/p53 circuitry exerts a potent tumor-suppressor function in the mammary gland by safeguarding against the emergence of cancer stem cells with unchecked self-renewal and tumorigenic potential.

Natural killer (NK) cells have antitumor, antiviral, and antibacterial functions, and efforts are being made to manipulate them in immunotherapeutic approaches. However, their activation mechanisms remain poorly defined, particularly during bacterial infections. Here, we show that upon lipopolysaccharide or E. coli exposure, dendritic cells (DCs) produce three cytokines-interleukin 2 (IL-2), IL-18, and interferon β (IFN-β)-necessary and sufficient for NK cell activation. IFN-β enhances NK cell activation by inducing IL-15 and IL-15 receptor α not only in DCs but, surprisingly, also in NK cells. This process allows the transfer of IL-15 on NK cell surface and its cis presentation. cis-presented NK cell-derived and trans-presented DC-derived IL-15 contribute equally to optimal NK cell activation.

Under the action of near-infrared radiation, shape anisotropic gold nanoparticles emit two-photon luminescence and release heat. Accordingly, they have been proposed for imaging, photothermal therapies and thermo-controlled drug delivery. In all these applications particular care must be given to control the nanoparticle − cell interaction and the thermal efficiency of the nanoparticles, while minimizing their intrinsic cytotoxicity. We present here the characterization of the cell interaction of newly developed branched gold nanostars, obtained by laurylsulfobetaine-driven seed-growth synthesis. The study provides information on the size distribution, the shape anisotropy, the cellular uptake and cytotoxicity of the gold nanostars as well as their intracellular dynamic behavior by means of two-photon luminescence imaging, fluorescence correlation spectroscopy and particle tracking. The results show that the gold nanostars are internalized as well as the widely used gold nanorods and are less toxic under prolonged treatments. At the same time they display remarkable twophoton luminescence and large extinction under polarized light in the near-infrared region of the spectrum, 800−950 nm. Gold nanostars appear then a valuable alternative to other elongated or in-homogeneous nanoparticles for cell imaging.

Natural killer (NK) cells are critical players against tumors. The outcome of anti-tumor vaccination protocols depends on the efficiency of NK-cell activation, and efforts are constantly made to manipulate them for immunotherapeutic approaches. Thus, a better understanding of NK-cell activation dynamics is needed. NK-cell interactions with accessory cells and trafficking between secondary lymphoid organs and tumoral tissues remain poorly characterized. Here, we show that upon triggering innate immunity with lipopolysaccharide (LPS), NK cells are transiently activated, leave the lymph node, and infiltrate the tumor, delaying its growth. Interestingly, NK cells are not actively recruited at the draining lymph node early after LPS administration, but continue their regular homeostatic turnover. Therefore, NK cells resident in the lymph node at the time of LPS administration become activated and exert anti-tumor functions. NK-cell activation correlates with the establishment of prolonged interactions with dendritic cells (DCs) in lymph nodes, as observed by two-photon microscopy. Close DC and NK-cell contacts are essential for the localized delivery of DC-derived IL-18 to NK cells, a strict requirement in NK-cell activation.