Natural killer (NK) cells are innate lymphocytes that directly kill tumor and pathogen-infected cells upon activation by cytokines and NK cell receptors (NKRs) without previous sensitization. It is known that cell metabolism affects the differentiation and effector functions of immune cells. For instance, interleukin−2 and interleukin−15 treatment increases glycolysis and oxidative phosphorylation (OXPHOS) in NK cells to support their effector functions. However, little is known about the metabolic reprogramming of human NK cells upon their activation by NKRs. In this study, we investigated the metabolism of NK cells stimulated via NKRs. We found that NK cells upregulated glycolysis and OXPHOS in response to anti-CD16 antibody or NKG2D ligand engagement. Inhibition of either glycolysis or OXPHOS impaired NK cell production of interferon-γ. Interestingly, inhibition of glycolysis but not OXPHOS decreased NK cell killing and dampened NK cell degranulation and Fas ligand expression, suggesting that glycolysis is more critical for NKR-activated cell cytotoxicity. Thus, our study provides insight into understanding the metabolic requirements underlying different effector functions of human NK cells.

Apart from their killer identity, natural killer (NK) cells have integral roles in shaping the tumor microenvironment. Through immune gene deconvolution, the present study revealed an interplay between NK cells and myeloid-derived suppressor cells (MDSCs) in nonresponders of immune checkpoint therapy. Given that the mechanisms governing the outcome of NK cell–to–myeloid cell interactions remain largely unknown, we sought to investigate the cross-talk between NK cells and suppressive myeloid cells. Upon contact with tumor-experienced NK cells, monocytes and neutrophils displayed increased expression of MDSC-related suppressive factors along with increased capacities to suppress T cells. These changes were accompanied by impaired antigen presentation by monocytes and increased ER stress response by neutrophils. In a cohort of patients with sarcoma and breast cancer, the production of interleukin-6 (IL-6) by tumor-infiltrating NK cells correlated with S100A8/9 and arginase-1 expression by MDSCs. At the same time, NK cell–derived IL-6 was associated with tumors with higher major histocompatibility complex class I expression, which we further validated with b2m -knockout (KO) tumor mice models. Similarly in syngeneic wild-type and IL-6 KO mouse models, we then demonstrated that the accumulation of MDSCs was influenced by the presence of such regulatory NK cells. Inhibition of the IL-6/signal transducer and activator of transcription 3 (STAT3) axis alleviated suppression of T cell responses, resulting in reduced tumor growth and metastatic dissemination. Together, these results characterize a critical NK cell–mediated mechanism that drives the development of MDSCs during tumor immune escape.

MicroRNAs (miRNAs) are short noncoding RNAs that regulate gene expression and are important for pre-B and follicular B lymphopoiesis as demonstrated, respectively, by mb-1-Cre– and cd19-Cre–mediated deletion of Dicer, the RNase III enzyme critical for generating mature miRNAs. To explore the role of miRNAs in B-cell terminal differentiation, we use Aicda-Cre to specifically delete Dicer in activated B cells where activation-induced cytidine deaminase is highly expressed. We demonstrate that mutant mice fail to produce high-affinity class-switched antibodies and generate memory B and long-lived plasma cells on immunization with a T cell–dependent antigen. More importantly, germinal center (GC) B-cell formation is drastically compromised in the absence of Dicer, as a result of defects in cell proliferation and survival. Dicer-deficient GC B cells express higher levels of cell cycle inhibitor genes and proapoptotic protein Bim. Ablation of Bim could partially rescue the defect in GC B-cell formation in Dicer-deficient mice. Taken together, our data suggest that Dicer and probably miRNAs are critical for GC B-cell formation during B-cell terminal differentiation.

Cell metabolism plays a pivotal role in regulating the effector functions of immune cells. Stimulatory cytokines, such as interleukin (IL)-2 or IL-12 and IL-15, activate glycolysis and oxidative phosphorylation in natural killer (NK) cells to support their enhanced effector functions. IL-10, a pleiotropic cytokine, is known to suppress macrophage activation but stimulate NK cells. However, it remains unclear if IL-10 has an effect on the metabolism of human NK cells and if so, what metabolic mechanisms are affected, and how these metabolic changes are regulated and contribute to the effector functions of NK cells. In this study, we demonstrate that IL-10 upregulates both glycolysis and oxidative phosphorylation in human NK cells, and these metabolic changes are crucial for the enhanced effector functions of NK cells. Mechanistically, we unravel that IL-10 activates the mammalian target of rapamycin complex 1 (mTORC1) to regulate metabolic reprogramming in human NK cells.

Natural Killer (NK) cells are a type of innate lymphoid cells that play a crucial role in immunity by killing virally infected or tumor cells and secreting cytokines and chemokines. NK cell-mediated immunotherapy has emerged as a promising approach for cancer treatment due to its safety and effectiveness. NK cell engagers (NKCEs), such as BiKE (bispecific killer cell engager) or TriKE (trispecific killer cell engager), are a novel class of antibody-based therapeutics that exhibit several advantages over other cancer immunotherapies harnessing NK cells. By bridging NK and tumor cells, NKCEs activate NK cells and lead to tumor cell lysis. A growing number of NKCEs are currently undergoing development, with some already in clinical trials. However, there is a need for more comprehensive studies to determine how the molecular design of NKCEs affects their functionality and manufacturability, which are crucial for their development as off-the-shelf drugs for cancer treatment. In this review, we summarize current knowledge on NKCE development and discuss critical factors required for the production of effective NKCEs.

Lipid rafts are plasma membrane microdomains that are enriched in cholesterol, glycosphingolipids, and glycosylphosphatidylinositol-anchored proteins and play an important role in the signaling of ITAM-bearing lymphocyte antigen receptors. Dectin-1 is a C-type lectin receptor (CLR) that recognizes beta-glucan in the cell walls of fungi and triggers signal transduction via its cytoplasmic hemi-ITAM. However, it is not known if similar to antigen receptors, Dectin-1 would also signal via lipid rafts and if the integrity of lipid raft microdomains is important for the physiological functions mediated by Dectin-1. We demonstrate here using sucrose gradient ultracentrifugation and confocal microscopy that Dectin-1 translocates to lipid rafts upon stimulation of dendritic cells (DCs) with the yeast derivative zymosan or beta-glucan. In addition, two key signaling molecules, Syk and PLCgamma2 are also recruited to lipid rafts upon the activation of Dectin-1, suggesting that lipid raft microdomains facilitate Dectin-1 signaling. Disruption of lipid raft integrity with the synthetic drug, methyl-beta-cyclodextrin (betamD) leads to reduced intracellular Ca2+ flux and defective Syk and ERK phosphorylation in Dectin-1-activated DCs. Furthermore, betamD-treated DCs have significantly attenuated production of IL-2, IL-10, and TNFalpha upon Dectin-1 engagement, and they also exhibit impaired phagocytosis of zymosan particles. Taken together, the data indicate that Dectin-1 and perhaps also other CLRs are recruited to lipid rafts upon activation and that the integrity of lipid rafts is important for the signaling and cellular functions initiated by this class of innate receptors.