Regulation Of Natural Killer Cell Development And Function By Activating Receptor Signaling Pathways

Natural killer (NK) cells are lymphocytes of the innate immune system that recognize and eliminate virally infected and transformed cells through their release of cytotoxic granules and production of inflammatory cytokines. The balance of intracellular signals received through NK cell activating and inhibitory receptors dictates these functions and generates target cell specificity during development. Many signaling pathways downstream of activating receptors contribute to these processes, however, what pathways and what signaling proteins contribute to NK cell development and function are not fully understood While NK cells do not possess an antigen-specific immunoreceptor, they do express a variety of germline-encoded activating and inhibitory receptors. MHC I-binding inhibitory receptors, including those of the Ly49 and KIR families, are expressed in a variegated manner, which creates ligand-specific diversity within the NK cell pool. In this thesis, I demonstrate that signals derived from activating receptors are critical for induction of Ly49 receptors/KIRs during NK cell development; activation signals through SLP-76 increased the probability of the Ly49 bi-directional Pro1 promoter to transcribe in the forward versus the reverse direction, leading to stable Ly49 receptor expression and receptor diversity in mature NK cells. Not only does activation through SLP-76 impact NK cell development, but downstream signaling pathways also impact NK cell function. Sustained Ca2+ signaling, known as store-operated Ca2+ entry (SOCE), occurs downstream of NK cell activating receptor engagement. CD8+ T cells require SOCE for cytokine production and cytotoxicity; however, less is known about its role in NK cells. In this thesis, I use mice deficient in STIM1/2, which are required for SOCE, to examine the contribution of sustained Ca2+ signaling to NK cell function. Surprisingly, we found that while SOCE is required for NK cell IFNγ production in an NFAT-dependent manner, NK cell degranulation and tumor rejection in vivo remained intact in the absence of SOCE. Our data suggest that mouse NK cells utilize different signaling mechanisms for cytotoxicity compared to other cytotoxic lymphocytes. In summary, NK cell activating receptor signals and downstream signaling pathways contribute greatly to the development and function of NK cells, allowing them to effectively eliminate cancer and virally infected cells

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Regulation of Natural Killer Cell Development and Function by Activating Receptor Signaling Pathways

Natural killer (NK) cells are lymphocytes of the innate immune system that recognize and eliminate virally infected and transformed cells through their release of cytotoxic granules and production of inflammatory cytokines. The balance of intracellular signals received through NK cell activating and inhibitory receptors dictates these functions and generates target cell specificity during development. Many signaling pathways downstream of activating receptors contribute to these processes, however, what pathways and what signaling proteins contribute to NK cell development and function are not fully understood. While NK cells do not possess an antigen-specific immunoreceptor, they do express a variety of germline-encoded activating and inhibitory receptors. MHC I-binding inhibitory receptors, including those of the Ly49 and KIR families, are expressed in a variegated manner, which creates ligand-specific diversity within the NK cell pool. In this thesis, I demonstrate that signals derived from activating receptors are critical for induction of Ly49 receptors/KIRs during NK cell development; activation signals through SLP-76 increased the probability of the Ly49 bi-directional Pro1 promoter to transcribe in the forward versus the reverse direction, leading to stable Ly49 receptor expression and receptor diversity in mature NK cells. Not only does activation through SLP-76 impact NK cell development, but downstream signaling pathways also impact NK cell function. Sustained Ca 2+ signaling, known as store-operated Ca2+ entry (SOCE), occurs downstream of NK cell activating receptor engagement. CD8+ T cells require SOCE for cytokine production and cytotoxicity; however, less is known about its role in NK cells. In this thesis, I use mice deficient in STIM1/2, which are required for SOCE, to examine the contribution of sustained Ca2+ signaling to NK cell function. Surprisingly, we found that while SOCE is required for NK cell IFNγ production in an NFAT-dependent manner, NK cell degranulation and tumor rejection in vivo remained intact in the absence of SOCE. Our data suggest that mouse NK cells utilize different signaling mechanisms for cytotoxicity compared to other cytotoxic lymphocytes. In summary, NK cell activating receptor signals and downstream signaling pathways contribute greatly to the development and function of NK cells, allowing them to effectively eliminate cancer and virally infected cells

Correction: Activating Receptor Signals Drive Receptor Diversity in Developing Natural Killer Cells.

[This corrects the article DOI: 10.1371/journal.pbio.1002526.]

Cutting Edge: Murine NK Cells Degranulate and Retain Cytotoxic Function without Store-Operated Calcium Entry

International audienceSustained Ca2+ signaling, known as store-operated calcium entry (SOCE), occurs downstream of immunoreceptor engagement and is critical for cytotoxic lymphocyte signaling and effector function. CD8(+) T cells require sustained Ca2+ signaling for inflammatory cytokine production and the killing of target cells; however, much less is known about its role in NK cells. In this study, we use mice deficient in stromal interacting molecules 1 and 2, which are required for SOCE, to examine the contribution of sustained Ca2+ signaling to murine NK cell function. Surprisingly, we found that, although SOCE is required for NK cell IFN-gamma production in an NFAT-dependent manner, NK cell degranulation/cytotoxicity and tumor rejection in vivo remained intact in the absence of sustained Ca2+ signaling. Our data suggest that mouse NK cells use different signaling mechanisms for cytotoxicity compared with other cytotoxic lymphocytes