Project description:Natural killer cells belong to the family of innate lymphoid cells comprising the frontline defense against infected and transformed cells. Development and activation of natural killer cells is highly dependent on interleukin-15 signaling. However, very little is known about the transcription program driving this process. The transcription factor Runx3 is highly expressed in natural killer cells, but its function in these cells is largely unknown. We show that loss of Runx3 impaired interleukin-15-dependent accumulation of mature natural killer cells in vivo and under culture conditions and pregnant Runx3(-/-) mice completely lack the unique population of interleukin-15-dependent uterine natural killer cells. Combined chromatin immunoprecipitation sequencing and differential gene expression analysis of wild-type versus Runx3-deficient in vivo activated splenic natural killer cells revealed that Runx3 cooperates with ETS and T-box transcription factors to drive the interleukin-15-mediated transcription program during activation of these cells. Runx3 functions as a nuclear regulator during interleukin-15-dependent activation of natural killer cells by regulating the expression of genes involved in proliferation, maturation, and migration. Similar studies with additional transcription factors will allow the construction of a more detailed transcriptional network that controls natural killer cell development and function.
Project description:Natural killer (NK) cells are important effector cells in the control of infections. The cellular and molecular signals required for NK cell activation in vivo remain poorly defined. By using a mouse model for the inducible ablation of dendritic cells (DCs), we showed that the in vivo priming of NK cell responses to viral and bacterial pathogens required the presence of CD11c(high) DCs. After peripheral Toll-like receptor (TLR) stimulation, NK cells were recruited to local lymph nodes, and their interaction with DCs resulted in the emergence of effector NK cells in the periphery. NK cell priming was dependent on the recognition of type I IFN signals by DCs and the subsequent production and trans-presentation of IL-15 by DCs to resting NK cells. CD11c(high) DC-derived IL-15 was necessary and sufficient for the priming of NK cells. Our data define a unique in vivo role of DCs for the priming of NK cells, revealing a striking and previously unappreciated homology to T lymphocytes of the adaptive immune system.
Project description:Physical and social environments influence immune homeostasis within adipose tissue, yet the mechanisms remain poorly defined. We report that an enriched environment (EE) housing modulates the immune cell population in white adipose tissue of mice including an increase in the abundance of natural killer (NK) cells. EE upregulates the expression of IL-15 and its receptor IL-15Rα specifically within mature adipocytes. Mechanistically, we show that hypothalamic brain-derived neurotrophic factor (BDNF) upregulates IL-15 production in adipocytes via sympathetic β-adrenergic signaling. Overexpressing BDNF mediated by recombinant adeno-associated virus (rAAV) vector in the hypothalamus expands adipose NK cells. Conversely, inhibition of hypothalamic BDNF signaling via gene transfer of a dominant negative TrkB receptor suppresses adipose NK cells. In white adipose tissue, overexpression of IL-15 using an adipocyte-specific rAAV vector stimulates adipose NK cells and inhibits the progression of subcutaneous melanoma, whereas local IL-15 knockdown blocks the EE effect. These results suggest that bio-behavioral factors regulate adipose NK cells via a hypothalamic BDNF-sympathoneural-adipocyte IL-15 axis. Targeting this pathway may have therapeutic significance for cancer.
Project description:The secondary analyses for correlates of risk of infection in the RV144 HIV-1 vaccine trial implicated vaccine-induced antibody-dependent cellular cytotoxicity (ADCC) responses in the observed protection, highlighting the importance of assessing such responses in ongoing and future HIV-1 vaccine trials. However, in vitro assays that detect ADCC activity in plasma from HIV-1 infected seropositive individuals are not always effective at detecting ADCC activity in plasma from HIV-1 vaccine recipients. In vivo, ADCC-mediating antibodies must operate at the site of infection, where effector cells are recruited and activated by a local milieu of chemokines and cytokines. Based on previous findings that interleukin 15 (IL-15) secretion increases during acute HIV-1 infection and enhances NK cell-mediated cytotoxicity, we hypothesized that IL-15 pretreatment of NK effector cells could be used to improve killing of infected cells by vaccine-induced antibodies capable of mediating ADCC. Using the HIV-1 infectious molecular clone (IMC)-infected target cell assay along with plasma samples from HIV-1 vaccine recipients, we found that IL-15 treatment of effector cells improved the ability of the vaccine-induced antibodies to recruit effector cells for ADCC. Through immunophenotyping experiments, we showed that this improved killing was likely due to IL-15 mediated activation of NK effector cells and higher intracellular levels of perforin and granzyme B in the IL-15 pretreated NK cells. We also found that using a 4-fold dilution series of plasma and subtraction of pre-vaccination responses resulted in lowest response rates among placebo recipients and significant separation between treatment groups. This represents the first attempt to utilize IL-15-treated effector cells and optimized analytical approaches to improve the detection of HIV-1 vaccine-induced ADCC responses and will inform analyses of future HIV vaccine clinical trials.
Project description:Cerebral malaria is a deadly complication of Plasmodium infection and involves blood brain barrier (BBB) disruption following infiltration of white blood cells. During experimental cerebral malaria (ECM), mice inoculated with Plasmodium berghei ANKA-infected red blood cells develop a fatal CM-like disease caused by CD8+ T cell-mediated pathology. We found that treatment with interleukin-15 complex (IL-15C) prevented ECM, whereas IL-2C treatment had no effect. IL-15C-expanded natural killer (NK) cells were necessary and sufficient for protection against ECM. IL-15C treatment also decreased CD8+ T cell activation in the brain and prevented BBB breakdown without influencing parasite load. IL-15C induced NK cells to express IL-10, which was required for IL-15C-mediated protection against ECM. Finally, we show that ALT-803, a modified human IL-15C, mediates similar induction of IL-10 in NK cells and protection against ECM. These data identify a regulatory role for cytokine-stimulated NK cells in the prevention of a pathogenic immune response.
Project description:Background:In the current study, we determined the effects of interleukin (IL)-21 on human natural killer (NK) cells and monocyte responses during Mycobacterium tuberculosis (Mtb) infection. Methods:We found that Mtb stimulated CD4+ and NK T cells from healthy individuals with latent tuberculosis infection (LTBI+) are major sources of IL-21. CD4+ cells from tuberculosis patients secreted less IL-21 than did CD4+ cells from healthy LTBI+ individuals. Interleukin-21 had no direct effect on Mtb-stimulated monocytes. Results:Interleukin-21-activated NK cells produced interferon (IFN)-γ, perforin, granzyme B, and granulysin; lysed Mtb-infected monocytes; and reduced Mtb growth. Interleukin-21-activated NK cells also enhanced IL-1β, IL-18, and CCL4/macrophage-inflammatory protein (MIP)-1β production and reduced IL-10 production by Mtb-stimulated monocytes. Recombinant IL-21 (1) inhibited Mtb growth, (2) enhanced IFN-γ, IL-1β, IL-18, and MIP-1β, and (3) reduced IL-10 expression in the lungs of Mtb-infected Rag2 knockout mice. Conclusions:These findings suggest that activated T cells enhance NK cell responses to lyse Mtb-infected human monocytes and restrict Mtb growth in monocytes through IL-21 production. Interleukin-21-activated NK cells also enhance the immune response by augmenting IL-1β, IL-18, and MIP-1β production and reducing IL-10 production by monocytes in response to an intracellular pathogen.