The Application of Drugs and Nano-Therapies Targeting Immune Cells in Hypoxic Inflammation

Immune cells are pivotal in the dynamic interplay between hypoxia and inflammation. During hypoxic conditions, HIF-1α, a crucial transcription factor, facilitates the adaptation of immune cells to the hypoxic micro-environment. This adaptation includes regulating immune cell metabolism, significantly impacting inflammation development. Strategies for anti-inflammatory and hypoxic relief have been proposed, aiming to disrupt the hypoxia-inflammation nexus. Research extensively focuses on anti-inflammatory agents and materials that target immune cells. These primarily mitigate hypoxic inflammation by encouraging M2-macrophage polarization, restraining neutrophil proliferation and infiltration, and maintaining Treg/TH17 balance. Additionally, oxygen-releasing nano-materials play a significant role. By alleviating hypoxia and clearing reactive oxygen species (ROS), these nano-materials indirectly influence immune cell functions. This paper delves into the response of immune cells under hypoxic conditions and the resultant effects on inflammation. It provides a comprehensive overview of various therapies targeting specific immune cells for anti-inflammatory purposes and explores nano-materials that either carry or generate oxygen to alleviate anoxic micro-environments.

Transcriptional signature of durable effector T cells elicited by a replication defective HCMV vaccine

Human cytomegalovirus (HCMV) is a leading infectious cause of birth defects and the most common opportunistic infection that causes life-threatening diseases post-transplantation; however, an effective vaccine remains elusive. V160 is a live-attenuated replication defective HCMV vaccine that showed a 42.4% efficacy against primary HCMV infection among seronegative women in a phase 2b clinical trial. Here, we integrated the multicolor flow cytometry, longitudinal T cell receptor (TCR) sequencing, and single-cell RNA/TCR sequencing approaches to characterize the magnitude, phenotype, and functional quality of human T cell responses to V160. We demonstrated that V160 de novo induces IE-1 and pp65 specific durable polyfunctional effector CD8 T cells that are comparable to those induced by natural HCMV infection. We identified a variety of V160-responsive T cell clones which exhibit distinctive "transient" and "durable" expansion kinetics, and revealed a transcriptional signature that marks durable CD8 T cells post-vaccination. Our study enhances the understanding of human T-cell immune responses to V160 vaccination.

CD39 (ENTPD1) in tumors: a potential therapeutic target and prognostic biomarker

As a regulator of the dynamic balance between immune-activated extracellular ATP and immunosuppressive adenosine, CD39 ectonucleotidase impairs the ability of immune cells to exert anticancer immunity and plays an important role in the immune escape of tumor cells within the tumor microenvironment. In addition, CD39 has been studied in cancer patients to evaluate the prognosis, the efficacy of immunotherapy (e.g., PD-1 blockade) and the prediction of recurrence. This article reviews the importance of CD39 in tumor immunology, summarizes the preclinical evidence on targeting CD39 to treat tumors and focuses on the potential of CD39 as a biomarker to evaluate the prognosis and the response to immune checkpoint inhibitors in tumors.

MAITabolism2 - the emerging understanding of MAIT cell metabolism and their role in metabolic disease

Mucosal associated invariant T (MAIT) cells are a population of unconventional innate T cells due to their non-MHC restriction and rapid effector responses. MAIT cells can recognise bacterial derived antigens presented on the MHC-like protein via their semi-restricted T cell receptor (TCR). Upon TCR triggering MAIT cells rapidly produce a range of effector molecules including cytokines, lytic granules and chemokines. This rapid and robust effector response makes MAIT cells critical in host responses against many bacterial pathogens. MAIT cells can also respond independent of their TCR via innate cytokines such as interleukin (IL)-18, triggering cytokine production, and are important in anti-viral responses. In addition to their protective role, MAIT cells have been implicated in numerous inflammatory diseases, including metabolic diseases often contributing to the pathogenesis via their robust cytokine production. Effector cells such as MAIT cells require significant amounts of energy to support their potent responses, and the type of nutrients available can dictate the functionality of the cell. Although data on MAIT cell metabolism is just emerging, several recent studies are starting to define the intrinsic metabolic requirements and regulators of MAIT cells. In this review we will outline our current understanding of MAIT cell metabolism, and outline their role in metabolic disease, and how disease-related changes in extrinsic metabolism can alter MAIT cell responses.

Potential pathogenic mechanism of type 1 X-linked lymphoproliferative syndrome caused by a mutation of SH2D1A gene in an infant: A case report

BACKGROUND

X-linked lymphoproliferative syndrome (XLP) is a rare X-linked recessive inborn errors of immunity. The pathogenesis of XLP might be related to phophatidylinositol-3-kinase (PI3K)-associated pathways but insight details remain unclear. This study was to study an infant XLP-1 case caused by a mutation in SH2D1A gene, investigate the structural and functional alteration of mutant SAP protein, and explore the potential role of PI3K-associated pathways in the progression of XLP-1.

METHODS

The proband's condition was monitored by laboratory and imagological examinations. Whole exome sequencing and Sanger sequencing were performed to detect the genetic disorder. Bioinformatics tools including PolyPhen-2, SWISS-MODEL and SWISS-PDB Viewer were used to predict the pathogenicity and estimate structural change of mutant protein. Flow cytometry was used to investigate expression of SAP and PI3K-associated proteins.

RESULTS

The proband was diagnosed with XLP-1 caused by a hemizygous mutation c.96G > T in SH2D1A gene resulting in a missense substitution of Arginine to Serine at the site of amino acid 32 (p.R32S). The mutant protein contained a hydrogen bond turnover at the site of mutation and was predicted to be highly pathogenic. Expression of SH2D1A encoded protein SAP was downregulated in proband. The PI3K-AKT-mTOR signaling pathway was fully activated in XLP-1 patients, but it was inactive or only partially activated in healthy people or HLH patients.

CONCLUSIONS

The mutation c.96G > T in SH2D1A gene caused structural and functional changes in the SAP protein, resulting in XLP-1. The PI3K-AKT-mTOR signaling pathway may play a role in XLP-1 pathogenesis.

Bacillus Calmette-Guérin in Immuno-Regulation of Alzheimer's Disease

Bacillus Calmette-Guérin is frequently the treatment of choice of superficial bladder cancer. Exposing the urinary bladder of elderly patients with bladder cancer to the BCG vaccine reduced the risk of Alzheimer's disease (AD) substantially. Vaccines against other infectious microorganisms by other vaccination methods showed a similar but a lesser effect. This suggests that immune effects on AD are antigenically non-specific, likely being a metabolic result of immune system activation, similar to that shown for Juvenile diabetes. In this mini review we point to the benefit of BCG vaccine. We then briefly highlight the pathological involvement of the immune system in the AD both, in the peripheral and the central (brain) compartments. Given the uncertain prophylactic mechanism of the BCG effect against AD we propose to take advantage of the therapeutically planned bladder exposure to BCG. Based on pathological aggregation of wrongly cleaved amyloid precursor protein (APP) resistant to the unfolded protein response (UPR) which results in amyloid beta plaques we predict that BCG may impact the UPR signaling cascade. In addition pathways of innate immunity training concerned with energy metabolism, predict capability of activated immune cells to substitute deranged astrocytes that fail to support neuronal energy metabolism. This mini review points to ways through which immune cells can mediate between BCG vaccination and AD to support the wellness of the central nervous system.

AKT Isoforms in the Immune Response in Cancer

AKT is a protein kinase that exists in three isoforms: AKT1, AKT2, and AKT3. Though similar in structure, these isoforms display different effects. AKT is activated downstream of PI3K, and together, this signaling pathway helps regulate cellular processes including cell growth, proliferation, metabolism, survival, and apoptosis. Disruption in these pathways has been associated with disorders including cardiovascular diseases, developmental disorders, inflammatory responses, autoimmune diseases, neurologic disorders, type 2 diabetes, and several cancers. In cancer, deregulation in the PI3K/AKT pathway can be manifested as tumorigenesis, pathological angiogenesis, and metastasis. Increased activity has been correlated with tumor progression and resistance to cancer treatments. Recent studies have suggested that inhibition of the PI3K/AKT pathway plays a significant role in the development, expansion, and proliferation of cells of the immune system. Additionally, AKT has been found to play an important role in differentiating regulatory T cells, activating B cells, and augmenting tumor immunosurveillance. This emphasizes AKT as a potential target for inhibition in cancer therapy. This chapter reviews AKT structure and regulation, its different isoforms, its role in immune cells, and its modulation in oncotherapy.

Pyruvate Kinase M2: a Metabolic Bug in Re-Wiring the Tumor Microenvironment

Metabolic reprogramming is a newly emerged hallmark of cancer attaining a recent consideration as an essential factor for the progression and endurance of cancer cells. A prime event of this altered metabolism is increased glucose uptake and discharge of lactate into the cells surrounding constructing a favorable tumor niche. Several oncogenic factors help in promoting this consequence including, pyruvate kinase M2 (PKM2) a rate-limiting enzyme of glycolysis in tumor metabolism via exhibiting its low pyruvate kinase activity and nuclear moon-lightening functions to increase the synthesis of lactate and macromolecules for tumor proliferation. Not only its role in cancer cells but also its role in the tumor microenvironment cells has to be understood for developing the small molecules against it which is lacking with the literature till date. Therefore, in this present review, the role of PKM2 with respect to various tumor niche cells will be clarified. Further, it highlights the updated list of therapeutics targeting PKM2 pre-clinically and clinically with their added limitations. This upgraded understanding of PKM2 may provide a pace for the reader in developing chemotherapeutic strategies for better clinical survival with limited resistance.

Acylglycerol Kinase Maintains Metabolic State and Immune Responses of CD8+ T Cells

CD8⁺ T cell expansions and functions rely on glycolysis, but the mechanisms underlying CD8⁺ T cell glycolytic metabolism remain elusive. Here, we show that acylglycerol kinase (AGK) is required for the establishment and maintenance of CD8⁺ T cell metabolic and functional fitness. AGK deficiency dampens CD8⁺ T cell antitumor functions in vivo and perturbs CD8⁺ T cell proliferation in vitro. Activation of phosphatidylinositol-3-OH kinase (PI3K)-mammalian target of rapamycin (mTOR) signaling, which mediates elevated CD8⁺ T cell glycolysis, is tightly dependent on AGK kinase activity. Mechanistically, T cell antigen receptor (TCR)- and CD28-stimulated recruitment of PTEN to the plasma membrane facilitates AGK-PTEN interaction and AGK-triggered PTEN phosphorylation, thereby restricting PTEN phosphatase activity in CD8⁺ T cells. Collectively, these results demonstrate that AGK maintains CD8⁺ T cell metabolic and functional state by restraining PTEN activity and highlight a critical role for AGK in CD8⁺ T cell metabolic programming and effector function.

Impaired enolase 1 glycolytic activity restrains effector functions of tumor-infiltrating CD8+ T cells

In the context of solid tumors, there is a positive correlation between the accumulation of cytotoxic CD8+ tumor-infiltrating lymphocytes (TILs) and favorable clinical outcomes. However, CD8+ TILs often exhibit a state of functional exhaustion, limiting their activity, and the underlying molecular basis of this dysfunction is not fully understood. Here, we show that TILs found in human and murine CD8+ melanomas are metabolically compromised with deficits in both glycolytic and oxidative metabolism. Although several studies have shown that tumors can outcompete T cells for glucose, thus limiting T cell metabolic activity, we report that a down-regulation in the activity of ENOLASE 1, a critical enzyme in the glycolytic pathway, represses glycolytic activity in CD8+ TILs. Provision of pyruvate, a downstream product of ENOLASE 1, bypasses this inactivity and promotes both glycolysis and oxidative phosphorylation, resulting in improved effector function of CD8+ TILs. We found high expression of both enolase 1 mRNA and protein in CD8+ TILs, indicating that the enzymatic activity of ENOLASE 1 is regulated posttranslationally. These studies provide a critical insight into the biochemical basis of CD8+ TIL dysfunction.

Amino acid-dependent cMyc expression is essential for NK cell metabolic and functional responses in mice

Natural killer (NK) cells are lymphocytes with important anti-tumour functions. Cytokine activation of NK cell glycolysis and oxidative phosphorylation (OXPHOS) are essential for robust NK cell responses. However, the mechanisms leading to this metabolic phenotype are unclear. Here we show that the transcription factor cMyc is essential for IL-2/IL-12-induced metabolic and functional responses in mice. cMyc protein levels are acutely regulated by amino acids; cMyc protein is lost rapidly when glutamine is withdrawn or when system L-amino acid transport is blocked. We identify SLC7A5 as the predominant system L-amino acid transporter in activated NK cells. Unlike other lymphocyte subsets, glutaminolysis and the tricarboxylic acid cycle do not sustain OXPHOS in activated NK cells. Glutamine withdrawal, but not the inhibition of glutaminolysis, results in the loss of cMyc protein, reduced cell growth and impaired NK cell responses. These data identify an essential role for amino acid-controlled cMyc for NK cell metabolism and function.

Ex vivo Akt inhibition promotes the generation of potent CD19CAR T cells for adoptive immunotherapy

Background

Insufficient persistence and effector function of chimeric antigen receptor (CAR)-redirected T cells have been challenging issues for adoptive T cell therapy. Generating potent CAR T cells is of increasing importance in the field. Studies have demonstrated the importance of the Akt pathway in the regulation of T cell differentiation and memory formation. We now investigate whether inhibition of Akt signaling during ex vivo expansion of CAR T cells can promote the generation of CAR T cells with enhanced antitumor activity following adoptive therapy in a murine leukemia xenograft model.

Methods

Various T cell subsets including CD8+ T cells, bulk T cells, central memory T cells and naïve/memory T cells were isolated from PBMC of healthy donors, activated with CD3/CD28 beads, and transduced with a lentiviral vector encoding a second-generation CD19CAR containing a CD28 co-stimulatory domain. The transduced CD19CAR T cells were expanded in the presence of IL-2 (50U/mL) and Akt inhibitor (Akti) (1 μM) that were supplemented every other day. Proliferative/expansion potential, phenotypical characteristics and functionality of the propagated CD19CAR T cells were analyzed in vitro and in vivo after 17-21 day ex vivo expansion. Anti-tumor activity was evaluated after adoptive transfer of the CD19CAR T cells into CD19+ tumor-bearing immunodeficient mice. Tumor signals were monitored with biophotonic imaging, and survival rates were analyzed by the end of the experiments.

Results

We found that Akt inhibition did not compromise CD19CAR T cell proliferation and expansion in vitro, independent of the T cell subsets, as comparable CD19CAR T cell expansion was observed after culturing in the presence or absence of Akt inhibitor. Functionally, Akt inhibition did not dampen cell-mediated effector function, while Th1 cytokine production increased. With respect to phenotype, Akti-treated CD19CAR T cells expressed higher levels of CD62L and CD28 as compared to untreated CD19CAR T cells. Once adoptively transferred into CD19+ tumor-bearing mice, Akti treated CD19CAR T cells exhibited more antitumor activity than did untreated CD19CAR T cells.

Conclusions

Inhibition of Akt signaling during ex vivo priming and expansion gives rise to CD19CAR T cell populations that display comparatively higher antitumor activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-017-0227-4) contains supplementary material, which is available to authorized users.

A quantitative transcriptomic analysis of the physiological significance of mTOR signaling in goat fetal fibroblasts

Background

Mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that is a central regulator of cell growth and metabolism. CCI-779 is a specific inhibitor of the mTORC1 signaling pathway.

Results

We performed comparative transcriptome profiling on Inner Mongolia Cashmere goat fetal fibroblasts (GFbs) that were treated with CCI-779 and untreated cells. A total of 365 differentially expressed genes (DEGs) appeared between untreated and CCI-779-treated GFbs, with an FDR ≤0.001 and fold-change ≥2. These 365 DEGs were associated with mTOR signaling; 144 were upregulated in CCI-779-treated cells, and 221 were downregulated.

Additionally, 300 genes were annotated with 43 Gene Ontology (GO) terms, and 293 genes were annotated with 194 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Three RNA polymerase II and polymerase III subunits, 3 transcription factors, and 5 kinases in mTOR signaling were differentially expressed in CCI-779-treated GFbs. Further 6 DEGs were related to amino acid metabolism, 11 mediated lipid metabolism, 11 participated in carbohydrate metabolism, and 5 were involved in single-nucleotide metabolism. Based on our quantitative transcriptomic analysis, 40 significant DEGs with important function related to metabolism, RNA polymerase, transcription factors and mTOR signaling were selected for qPCR analysis, and the quantitative results between the two analysis methods were concordant. The qPCR data confirmed the differential expression in the RNA-Seq experiments. To validate the translational significance of the findings in certain differentially expressed genes, S6K1 and VEGF were detected by western blot, and these two proteins showed a differential expression between non-treated and treated with CCI-779 groups, which were consistent with mRNA abundance. The data showed a preliminary significance of the findings in the protein levels.

Conclusions

CCI-779 induces transcriptomic changes, and mTOR signaling might have significant function in the activation of RNA polymerase and certain transcription factors and in the metabolism of amino acids, lipids, carbohydrates, and single nucleotides in GFbs. These data filled the vacancy in the systematical profiling of mTOR signaling on Cashmere goat fetal fibroblasts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3151-y) contains supplementary material, which is available to authorized users.

Embryonic liver fordin is involved in glucose glycolysis of hepatic stellate cell by regulating PI3K/Akt signaling

AIM

To investigate the role of embryonic liver fordin (ELF) in liver fibrosis by regulating hepatic stellate cells (HSCs) glucose glycolysis.

METHODS

The expression of ELF and the glucose glycolysis-related proteins were evaluated in activated HSCs. siRNA was used to silence ELF expression in activated HSCs in vitro and the subsequent changes in PI3K/Akt signaling and glucose glycolysis-related proteins were observed.

RESULTS

The expression of ELF increased remarkably in HSCs of the fibrosis mouse model and HSCs that were cultured for 3 wk in vitro. Glucose glycolysis-related proteins showed an obvious increase in the activated HSCs, such as phosphofructokinase, platelet and glucose transporter 1. ELF-siRNA, which perfectly silenced the expression of ELF in activated HSCs, led to the induction of glucose glycolysis-related proteins and extracellular matrix (ECM) components. Moreover, pAkt, which is an important downstream factor in PI3K/Akt signaling, showed a significant change in response to the ELF silencing. The expression of glucose glycolysis-related proteins and ECM components decreased remarkably when the PI3K/Akt signaling was blocked by Ly294002 in the activated HSCs.

CONCLUSION

ELF is involved in HSC glucose glycolysis by regulating PI3K/Akt signaling.

Gene expression profiling of CD8+ T cells induced by ovarian cancer cells suggests a possible mechanism for CD8+ Treg cell production

OBJECTIVES

The aim of this study was to investigate a possible mechanism of CD8⁺ regulatory T-cell (Treg) production in an ovarian cancer (OC) microenvironment.

MATERIALS AND METHODS

Agilent microarray was used to detect changes in gene expression between CD8⁺ T cells cultured with and without the SKOV3 ovarian adenocarcinoma cell line. QRT-PCR was performed to determine glycolysis gene expression in CD8⁺ T cells from a transwell culturing system and OC patients. We also detected protein levels of glycolysis-related genes using Western blot analysis.

RESULTS

Comparing gene expression profiles revealed significant differences in expression levels of 1420 genes, of which 246 were up-regulated and 1174 were down-regulated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis indicated that biological processes altered in CD8⁺ Treg are particularly associated with energy metabolism. CD8⁺ Treg cells induced by co-culture with SKOV3 had lower glycolysis gene expression compared to CD8⁺ T cells cultured alone. Glycolysis gene expression was also decreased in the CD8⁺ T cells of OC patients.

CONCLUSIONS

These findings provide a comprehensive bioinformatics analysis of DEGs in CD8⁺ T cells cultured with and without SKOV3 and suggests that metabolic processes may be a possible mechanism for CD8⁺ Treg induction.

Akt inhibition enhances expansion of potent tumor-specific lymphocytes with memory cell characteristics

Adoptive cell therapy (ACT) using autologous tumor-infiltrating lymphocytes (TIL) results in complete regression of advanced cancer in some patients, but the efficacy of this potentially curative therapy may be limited by poor persistence of TIL after adoptive transfer. Pharmacologic inhibition of the serine/threonine kinase Akt has recently been shown to promote immunologic memory in virus-specific murine models, but whether this approach enhances features of memory (e.g., long-term persistence) in TIL that are characteristically exhausted and senescent is not established. Here, we show that pharmacologic inhibition of Akt enables expansion of TIL with the transcriptional, metabolic, and functional properties characteristic of memory T cells. Consequently, Akt inhibition results in enhanced persistence of TIL after adoptive transfer into an immunodeficient animal model and augments antitumor immunity of CD8 T cells in a mouse model of cell-based immunotherapy. Pharmacologic inhibition of Akt represents a novel immunometabolomic approach to enhance the persistence of antitumor T cells and improve the efficacy of cell-based immunotherapy for metastatic cancer.

PI3K signalling in inflammation

PI3Ks regulate several key events in the inflammatory response to damage and infection. There are four Class I PI3K isoforms (PI3Kα,β,γ,δ), three Class II PI3K isoforms (PI3KC2α, C2β, C2γ) and a single Class III PI3K. The four Class I isoforms synthesise the phospholipid 'PIP3'. PIP3 is a 'second messenger' used by many different cell surface receptors to control cell movement, growth, survival and differentiation. These four isoforms have overlapping functions but each is adapted to receive efficient stimulation by particular receptor sub-types. PI3Kγ is highly expressed in leukocytes and plays a particularly important role in chemokine-mediated recruitment and activation of innate immune cells at sites of inflammation. PI3Kδ is also highly expressed in leukocytes and plays a key role in antigen receptor and cytokine-mediated B and T cell development, differentiation and function. Class III PI3K synthesises the phospholipid PI3P, which regulates endosome-lysosome trafficking and the induction of autophagy, pathways involved in pathogen killing, antigen processing and immune cell survival. Much less is known about the function of Class II PI3Ks, but emerging evidence indicates they can synthesise PI3P and PI34P2 and are involved in the regulation of endocytosis. The creation of genetically-modified mice with altered PI3K signalling, together with the development of isoform-selective, small-molecule PI3K inhibitors, has allowed the evaluation of the individual roles of Class I PI3K isoforms in several mouse models of chronic inflammation. Selective inhibition of PI3Kδ, γ or β has each been shown to reduce the severity of inflammation in one or more models of autoimmune disease, respiratory disease or allergic inflammation, with dual γ/δ or β/δ inhibition generally proving more effective. The inhibition of Class I PI3Ks may therefore offer a therapeutic opportunity to treat non-resolving inflammatory pathologies in humans. This article is part of a Special Issue entitled Phosphoinositides.

DCs sensitized with mPD-L1-Ig fusion protein improve the effect of heart transplantation in mice by promoting the generation of T-reg cells

PURPOSE

To detect the effects of DCs sensitized by mPD-L1-Ig fusion protein in heart transplantation in mice as well as its mechanisms.

METHOD

The mPD-L1-IgG1 construct was used to build a yeast expression system, and the fusion protein was expressed by secretion after the transfection of the GS115 yeast strain, purified by affinity chromatography and ion exchange chromatography, and assayed by SDS-PAGE and Western blot. The ability of the fusion protein to bind to the acceptor PD-1 was tested by ELISA, and the ability of the fusion protein to inhibit the function of T cells was tested by mixed lymphocyte reaction (MLR).

RESULTS

We used the new PD-L1-IgG1 fusion protein to sensitize imDCs and maintained the immature state of DCs, so as to induce stable and effective immune tolerance to heart transplantation. After the treatment of DCs by mPD-L1-Ig in vitro, the levels of CD80, CD40 and I-Ab expression on DCs are relatively weaker, the ability of DCs to stimulates the proliferation of allogeneic spleen T cells was significantly decreased (P<0.01), and the levels of Th1 (IL-2, IFN-γ) and Th2 (IL-4, IL-10) secreted by induced allogeneic T cells were significantly decreased (P<0.01). An in vivo experiment also revealed that DCs sensitized by mPD-L1-IgG1 could prolong the survival time of a transplanted heart to 17.8±1.12days, and alleviate the pathological change of the cardiac allografts compared with other three groups.

CONCLUSION

DCs sensitized by the yeast-expressed mPD-L1-Ig fusion protein are shown to alleviate the cardiac allograft rejection in mice.

The role of mechanistic target of rapamycin (mTOR) complexes signaling in the immune responses

The mechanistic Target of Rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase which is a member of the PI3K related kinase (PIKK) family. mTOR emerged as a central node in cellular metabolism, cell growth, and differentiation, as well as cancer metabolism. mTOR senses the nutrients, energy, insulin, growth factors, and environmental cues and transmits signals to downstream targets to effectuate the cellular and metabolic response. Recently, mTOR was also implicated in the regulation of both the innate and adaptive immune responses. This paper will summarize the current knowledge of mTOR, as related to the immune microenvironment and immune responses.