Reactive oxygen species (ROS) are byproducts of aerobic metabolism and contribute to both physiological and pathological conditions as second messengers. ROS are essential for activation of T cells, ...but how ROS influence NKT cells is unknown. In the present study, we investigated the role of ROS in NKT cell function. We found that NKT cells, but not CD4 or CD8 T cells, have dramatically high ROS in the spleen and liver of mice but not in the thymus or adipose tissues. Accordingly, ROS-high NKT cells exhibited increased susceptibility and apoptotic cell death with oxidative stress. High ROS in the peripheral NKT cells were primarily produced by NADPH oxidases and not mitochondria. We observed that sorted ROS-high NKT cells were enriched in NKT1 and NKT17 cells, whereas NKT2 cells were dominant in ROS-low cells. Furthermore, treatment of NKT cells with antioxidants led to reduced frequencies of IFN-γ- and IL-17-expressing cells, indicating that ROS play a role in regulating the inflammatory function of NKT cells. The transcription factor promyelocytic leukemia zinc finger (PLZF) seemed to control the ROS levels. NKT cells from adipose tissues that do not express PLZF and those from PLZF haplodeficient mice have low ROS. Conversely, ROS were highly elevated in CD4 T cells from mice ectopically expressing PLZF. Thus, our findings demonstrate that PLZF controls ROS levels, which in turn governs the inflammatory function of NKT cells.
Cellular metabolism and signaling pathways are key regulators to determine conventional T cell fate and function, but little is understood about the role of cell metabolism for natural killer T (NKT) ...cell survival, proliferation, and function. We found that NKT cells operate distinct metabolic programming from CD4 T cells. NKT cells are less efficient in glucose uptake than CD4 T cells with or without activation. Gene-expression data revealed that, in NKT cells, glucose is preferentially metabolized by the pentose phosphate pathway and mitochondria, as opposed to being converted into lactate. In fact, glucose is essential for the effector functions of NKT cells and a high lactate environment is detrimental for NKT cell survival and proliferation. Increased glucose uptake and IFN-γ expression in NKT cells is inversely correlated with bacterial loads in response to bacterial infection, further supporting the significance of glucose metabolism for NKT cell function. We also found that promyelocytic leukemia zinc finger seemed to play a role in regulating NKT cells’ glucose metabolism. Overall, our study reveals that NKT cells use distinct arms of glucose metabolism for their survival and function.
T lymphocytes rely on several metabolic processes to produce the high amounts of energy and metabolites needed to drive clonal expansion and the development of effector functions. However, many of ...these pathways result in the production of reactive oxygen species (ROS), which have canonically been thought of as cytotoxic agents due to their ability to damage DNA and other subcellular structures. Interestingly, ROS has recently emerged as a critical second messenger for T cell receptor signaling and T cell activation, but the sensitivity of different T cell subsets to ROS varies. Therefore, the tight regulation of ROS production by cellular antioxidant pathways is critical to maintaining proper signal transduction without compromising the integrity of the cell. This review intends to detail the common metabolic sources of intracellular ROS and the mechanisms by which ROS contributes to the development of T cell-mediated immunity. The regulation of ROS levels by the glutathione pathway and the Nrf2-Keap1-Cul3 trimeric complex will be discussed. Finally, T cell-mediated autoimmune diseases exacerbated by defects in ROS regulation will be further examined in order to identify potential therapeutic interventions for these disorders.
IL-10 produced by dendritic cells (DC) can limit or terminate ongoing inflammatory responses by inhibiting the proinflammatory cytokine production. Currently, the molecular mechanism by which IL-10 ...suppresses cytokine production is still ill-defined. In this study, we showed that IL-10 produced by DC dampens myeloid differentiation factor (MyD)88-dependent, but not MyD88-independent signaling. At the molecular level, IL-10 induces ubiquitination and subsequent protein degradation of MyD88-dependent signaling molecules, including IL-1 receptor-associated kinase 4 and TNF-receptor associated factor 6. Protein degradation by IL-10 was associated with decreased phosphorylation of p38, JNK, and IKK. All of these events were prevented by either blocking IL-10 receptor signaling or inhibiting proteasome degradation. IL-10 induced LPS hyporesponsiveness using the same mechanisms, i.e., ubiquitination and protein degradation. Thus, a previously undescribed regulatory mechanism by which IL-10-mediated protein degradation contributes to the inhibition of inflammatory cytokine production and endotoxin tolerance in DC.
HIV-1 gene expression is regulated by host and viral factors that interact with viral motifs and is influenced by proviral integration sites. Here, expression variation among integrants was followed ...for hundreds of individual proviral clones within polyclonal populations throughout successive rounds of virus and cultured cell replication, with limited findings using CD4+ cells from donor blood consistent with observations in immortalized cells. Tracking clonal behavior by proviral "zip codes" indicated that mutational inactivation during reverse transcription was rare, while clonal expansion and proviral expression states varied widely. By sorting for provirus expression using a GFP reporter in the nef open reading frame, distinct clone-specific variation in on/off proportions were observed that spanned three orders of magnitude. Tracking GFP phenotypes over time revealed that as cells divided, their progeny alternated between HIV transcriptional activity and non-activity. Despite these phenotypic oscillations, the overall GFP+ population within each clone was remarkably stable, with clones maintaining clone-specific equilibrium mixtures of GFP+ and GFP- cells. Integration sites were analyzed for correlations between genomic features and the epigenetic phenomena described here. Integrants inserted in the sense orientation of genes were more frequently found to be GFP negative than those in the antisense orientation, and clones with high GFP+ proportions were more distal to repressive H3K9me3 peaks than low GFP+ clones. Clones with low frequencies of GFP positivity appeared to expand more rapidly than clones for which most cells were GFP+, even though the tested proviruses were Vpr-. Thus, much of the increase in the GFP- population in these polyclonal pools over time reflected differential clonal expansion. Together, these results underscore the temporal and quantitative variability in HIV-1 gene expression among proviral clones that are conferred in the absence of metabolic or cell-type dependent variability, and shed light on cell-intrinsic layers of regulation that affect HIV-1 population dynamics.
Myeloid differentiation primary response protein 88 (MyD88) is classically known as an adaptor, linking TLR and IL-1R to downstream signaling pathways in the innate immune system. In addition to its ...role in innate immune cells, MyD88 has been shown to play an important role in T cells. How MyD88 regulates helper T-cell differentiation remains largely unknown, however. Here we demonstrate that MyD88 is an important regulator of IL-17-producing CD4⁺ T helper cells (Th17) cell proliferation. MyD88-deficient CD4⁺ T cells showed a defect in Th17 cell differentiation, but not in Th1 cell or Th2 cell differentiation. The impaired IL-17 production from MyD88-deficient CD4⁺ T cells is not a result of defective RAR-related orphan receptor yt (RORyt) expression. Instead, MyD88 is essential for sustaining the mammalian target of rapamycin (mTOR) activation necessary to promote Th17 cell proliferation by linking IL-1 and IL-23 signaling. MyD88-deficient CD4⁺ T cells showed impaired mTOR activation and, consequently, reduced Th17 cell proliferation. Importantly, the absence of MyD88 in T cells ameliorated disease in the experimental autoimmune encephalomyelitis model. Taken together, our results demonstrate that MyD88 has a dual function in Th17 cells by delivering IL-1 signaling during the early differentiation stage and integrating IL-23 signaling to the mTOR complex to expand committed Th17 cells.
Iron has long been established as a critical mediator of T cell development and proliferation. However, the mechanisms by which iron controls CD4 T cell activation and expansion remain poorly ...understood. In this study, we show that stimulation of CD4 T cells from C57BL/6 mice not only decreases total and labile iron levels but also leads to changes in the expression of iron homeostatic machinery. Additionally, restraining iron availability in vitro severely inhibited CD4 T cell proliferation and cell cycle progression. Although modulating cellular iron levels increased IL-2 production by activated T lymphocytes, CD25 expression and pSTAT5 levels were decreased, indicating that iron is necessary for IL-2R-mediated signaling. We also found that iron deprivation during T cell stimulation negatively impacts mitochondrial function, which can be reversed by iron supplementation. In all, we show that iron contributes to activation-induced T cell expansion by positively regulating IL-2R signaling and mitochondrial function.
We show the presence of lymphoid tissue‐resident PLZF+CD45RA+RO+CD4 T cells in humans. They express HLA‐DR, granzyme B, and perforin and are low on CCR7 like terminally differentiated effector memory ...(Temra) cells and are likely generated from effector T cells (Te) or from central (Tcm) or effector (Tem) memory T (Tcm) cells during immune responses. Tn, Naïve T cells.
AbstractA multi-centre, randomised, double-blinded, active-controlled, parallel-group clinical trial was carried out to assess the immunogenicity and safety of NBP608—a newly developed ...live-attenuated zoster vaccine in Korea—relative to Zostavax® in healthy adults aged 50 years or older. Immune responses to the vaccine were evaluated by glycoprotein enzyme-linked immunosorbent assay (gpELISA) and enzyme-linked immunosorbent spot (ELISPOT) assays using the interferon (IFN)-γ and interleukin (IL)-2 FluoroSpot kit 6 weeks after vaccination. Safety was monitored for 26 weeks based on subjects’ diaries, spontaneous reports from subjects, and history taking by the investigators. A total of 845 subjects participated in the screening, and 823 received the vaccination (413 in the NBP608 group and 411 in the comparator group). The gpELISA-determined geometric mean fold rise from baseline to post NBP608 vaccination was 2.75 95% confidence interval, CI (2.57, 2.94). The gpELISA-determined adjusted geometric mean titers (GMTs) of NBP608 and the comparator were 1346.37 95% CI (1273.99, 1422.87) and 1674.94 95% CI (1585.35, 1769.58), respectively. The adjusted GMT ratio of NBP608 to the comparator was 0.80 95% CI (0.75, 0.87). There was no statistically significant difference between two groups in terms of the geometric mean spot numbers determined by IFN-γ and IL-2 ELISPOT assays at 6 weeks post vaccination (P = 0.7232, 0.3844). The incidence of adverse events (AEs) within 6 weeks post vaccination was 49.82% overall (410/823, 941 cases), 50.73% (209/412, 474 cases) in the NBP608 group, and 48.91% (201/411, 467 cases) in the comparator group. The difference in AE rate between the two groups was not statistically significant (P = 0.6010). Most AEs were mild, with a rate of 83.12% in the NBP608 group and 75.37% in the comparator group. Thus, NBP608 is non-inferior to Zostavax® in terms of inducing the immune response and can be safely administered to adults aged 50 years or older. ClinicalTrials.gov Identifier: NCT03120364.
Natural killer T (NKT) cells operate distinctly different metabolic programming from CD4 T cells, including a strict requirement for glutamine to regulate cell homeostasis. However, the underlying ...mechanisms remain unknown. Here, we report that at a steady state, NKT cells have higher glutamine levels than CD4 T cells and that NKT cells increase glutaminolysis on activation. Activated NKT cells use glutamine to fuel the tricarboxylic acid cycle and glutathione synthesis. In addition, glutamine-derived nitrogen enables protein glycosylation via the hexosamine biosynthesis pathway (HBP). Each of these branches of glutamine metabolism seems to be critical for NKT cell homeostasis and mitochondrial functions. Glutaminolysis and HBP differentially regulate interleukin-4 (IL-4) and interferon γ (IFNγ) production. Glutamine metabolism appears to be controlled by AMP-activated protein kinase (AMPK)-mammalian target of rapamycin complex 1 (mTORC1) signaling. These findings highlight a distinct metabolic requirement of NKT cells compared with CD4 T cells, which may have therapeutic implications in the treatment of certain nutrient-restricted diseases.
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•Glutamine-enabled TCA cycle, GSH synthesis, and HBP are critical for NKT cell homeostasis•Glutaminolysis and HBP differentially regulate IL-4 and IFNγ production by NKT cells•Glutamine metabolism in NKT cells appears to be controlled by AMPK-mTORC1 signaling
Kumar et al. report that NKT cells rely on glutamine for their homeostasis and functions. Glutamine does this by supporting mitochondrial functions, maintaining redox balance, and supporting glycosylation processes in NKT cells.
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