Inflammation is a critical component of the immune response. However, acute or chronic inflammation can be highly destructive. Uncontrolled inflammation forms the basis for allergy, asthma and various autoimmune disorders. Here we identified a signaling pathway that was exclusively responsible for the production of inflammatory cytokines but not for cytotoxicity. Recognition of tumor cells expressing the NK cell-activatory ligands H60 or CD137L by mouse natural killer (NK) cells led to efficient cytotoxicity and the production of inflammatory cytokines. Both of those effector functions required the kinases Lck, Fyn and PI(3)K (subunits p85α and p110δ) and the signaling protein PLC-γ2. However, a complex of Fyn and the adaptor ADAP exclusively regulated the production of inflammatory cytokines but not cytotoxicity in NK cells. That unique function of ADAP required a Carma1-Bcl-10-MAP3K7 signaling axis. Our results have identified molecules that can be targeted to regulate inflammation without compromising NK cell cytotoxicity.

One of the mechanisms by which tumors evade immune surveillance is through shedding of the major histocompatibility complex (MHC) class I chain-related protein A and B (MICA/B) from their cell surface. MICA/B are ligands for the activating receptor NKG2D on NK and CD8 T cells. This shedding reduces cell surface levels of MICA/B and impairs NKG2D recognition. Shed MICA/B can also mask NKG2D receptor and is thought to induce NKG2D internalization, further compromising immune surveillance by NK cells.

Influenza virus targets epithelial cells in the upper respiratory tract. Natural Killer (NK) cell-mediated early innate defense responses to influenza infection include the killing of infected epithelial cells and generation of anti-viral cytokines including interferon gamma (IFN-γ). To date, it is unclear how the underlying cytokine milieu during infection regulates NK cell effector functions. Our data show during influenza infection myeloid cell-derived IL-27 regulates the early-phase effector functions of NK cells in the bronchioalveolar and lung tissue. Lack of IL-27R (Il27ra-/-) or IL-27 (Ebi3-/-) resulted in impaired NK cell effector functions including the generation of anti-viral IFN-γ responses. We identify CD27+CD11b+ NK cells as the primary subset that expresses IL-27R, which predominantly produces IFN-γ within the upper respiratory tract of the infected mice. IL-27 alone was incapable of altering the effector functions of NK cells. However, IL-27 sensitizes NK cells to augment both in vitro and in vivo responses mediated via the NKG2D receptor. This 'priming' function of IL-27 is mediated partly via transcriptional pathways regulated by Mafs and Nrf2 transcriptionally regulating TFAM and CPT1. Our data for the first time establishes a novel role for IL-27 in regulating early-phase effector functions of NK cells during influenza infection.

Phosphoinositide 3-kinases (PI3Ks) are promising targets for therapeutic development in cancer. The class I PI3K isoform p110α has received considerable attention in oncology because the gene encoding p110α (PIK3CA) is frequently mutated in human cancer. However, little is known about the function of p110α in lymphocyte populations that modulate tumorigenesis. We used recently developed investigational inhibitors to compare the function of p110α and other isoforms in natural killer (NK) cells, a key cell type for immunosurveillance and tumor immunotherapy. Inhibitors of all class I isoforms (pan-PI3K) significantly impaired NK cell-mediated cytotoxicity and antibody-dependent cellular cytotoxicity against tumor cells, whereas p110α-selective inhibitors had no effect. In NK cells stimulated through NKG2D, p110α inhibition modestly reduced PI3K signaling output as measured by AKT phosphorylation. Production of IFN-γ and NK cell-derived chemokines was blocked by a pan-PI3K inhibitor and partially reduced by a p110δinhibitor, with lesser effects of p110α inhibitors. Oral administration of mice with MLN1117, a p110α inhibitor in oncology clinical trials, had negligible effects on NK subset maturation or terminal subset commitment. Collectively, these results support the targeting of PIK3CA mutant tumors with selective p110α inhibitors to preserve NK cell function.

Recent advances in single-cell technologies and an improved understanding of tumor antigens have empowered researchers to investigate tumor antigen-specific CD8+ T cells at the single-cell level. Peptide-MHC I tetramers are often utilized to enrich antigen-specific CD8+ T cells, which however, introduces the undesired risk of altering their clonal distribution or their transcriptional state. This study addresses the feasibility of utilizing tetramers to enrich antigen-specific CD8+ T cells for single-cell analysis.

The intracellular spatiotemporal organization of signaling events is critical for normal cellular function. In response to environmental stimuli, cells utilize highly organized signaling pathways that are subject to multiple layers of regulation. However, the molecular mechanisms that coordinate these complex processes remain an enigma. Scaffolding proteins (scaffolins) have emerged as critical regulators of signaling pathways, many of which have well-described functions in immune cells. IQGAP1, a highly conserved cytoplasmic scaffold protein, is able to curb, compartmentalize, and coordinate multiple signaling pathways in a variety of cell types. IQGAP1 plays a central role in cell-cell interaction, cell adherence, and movement via actin/tubulin-based cytoskeletal reorganization. Evidence also implicates IQGAP1 as an essential regulator of the MAPK and Wnt/β-catenin signaling pathways. Here, we summarize the recent advances on the cellular and molecular biology of IQGAP1. We also describe how this pleiotropic scaffolin acts as a true molecular puppeteer, and highlight the significance of future research regarding the role of IQGAP1 in immune cells.

Immune-checkpoint protein V-domain immunoglobulin suppressor of T-cell activation (VISTA) controls antitumor immunity and is a valuable target for cancer immunotherapy. This study identified a role of VISTA in regulating Toll-like receptor (TLR) signaling in myeloid cells and controlling myeloid cell-mediated inflammation and immunosuppression. VISTA modulated the polyubiquitination and protein expression of TRAF6. Consequently, VISTA dampened TLR-mediated activation of MAPK/AP-1 and IKK/NF-κB signaling cascades. At cellular levels, VISTA regulated the effector functions of myeloid-derived suppressor cells and tolerogenic dendritic cell (DC) subsets. Blocking VISTA augmented their ability to produce proinflammatory mediators and diminished their T cell-suppressive functions. These myeloid cell-dependent effects resulted in a stimulatory tumor microenvironment that promoted T-cell infiltration and activation. We conclude that VISTA is a critical myeloid cell-intrinsic immune-checkpoint protein and that the reprogramming of tolerogenic myeloid cells following VISTA blockade promotes the development of T cell-mediated antitumor immunity.