Peripheral bloodCD56brightNKcells respond to stem cell factor and adhere to its membrane‐bound form after upregulation of c‐kit

Phosphodiesterase 4A confers resistance to PGE2-mediated suppression in CD25+ /CD54+ NK cells

Inadequate persistence of tumor‐infiltrating natural killer (NK) cells is associated with poor prognosis in cancer patients. The solid tumor microenvironment is characterized by the presence of immunosuppressive factors, including prostaglandin E2 (PGE2), that limit NK cell persistence. Here, we investigate if the modulation of the cytokine environment in lung cancer with IL‐2 or IL‐15 renders NK cells resistant to suppression by PGE2. Analyzing Cancer Genome Atlas (TCGA) data, we found that high NK cell gene signatures correlate with significantly improved overall survival in patients with high levels of the prostaglandin E synthase (PTGES). In vitro, IL‐15, in contrast to IL‐2, enriches for CD25⁺/CD54⁺ NK cells with superior mTOR activity and increased expression of the cAMP hydrolyzing enzyme phosphodiesterase 4A (PDE4A). Consequently, this distinct population of NK cells maintains their function in the presence of PGE2 and shows an increased ability to infiltrate lung adenocarcinoma tumors in vitro and in vivo. Thus, strategies to enrich CD25⁺/CD54⁺ NK cells for adoptive cell therapy should be considered.

An Inverse Relationship Between c-Kit/CD117 and mTOR Confers NK Cell Dysregulation Late After Severe Injury

Major trauma-induced tissue injury causes a dysregulation of the immune system. Severe systemic inflammation occurs early after the insult. Later on, an enhanced risk for life-threatening opportunistic infections develops that culminates at the end of the first week after trauma. CD56^bright Natural killer (NK) cells play a key role in the defense against infection due to their rapid release of Interferon (IFN) γ in response to Interleukin (IL) 12. NK cells are impaired in IFN-γ synthesis after severe injury due to a disturbed IL-12/IFN-γ axis. Thereby, a circulating factor mediates extrinsic suppression of NK cells. Yet unknown cell-intrinsic mechanisms manifest by day 8 after trauma and render NK cells unresponsive to stimulatory cytokines. In the present study, we investigated the origin of such late NK cell-intrinsic suppression after major trauma. Peripheral blood mononuclear cells (PBMC) were isolated from patients 8 day after severe injury and from healthy control subjects and were stimulated with inactivated Staphylococcus aureus. The expression of diverse cytokine receptors, intracellular signaling molecules, and the secretion of IFN-γ by CD56^bright NK cells were examined. After stimulation with S. aureus, NK cells from patients expressed enhanced levels of c-kit/CD117 that inversely correlated with IFN-γ synthesis and IL-12 receptor (IL-12R) β2 expression. Supplementation with IL-15 and inhibition of the transforming growth factor receptor (TGF-βR) I reduced CD117 expression and increased the level of IL-12Rβ2 and IFN-γ. NK cells from patients showed reduced phosphorylation of mammalian target of rapamycin (mTOR). Addition of IL-15 at least partly restored mTOR phosphorylation and increased IL-12Rβ2 expression. The reduced mTOR phosphorylation after severe injury was cell-intrinsic as it was not induced by serum factors. Inhibition of mTOR in purified NK cells from healthy donors by rapamycin decreased the synthesis of IFN-γ. Thus, impaired mTOR phosphorylation in response to a microbial challenge contributes to the cell-intrinsic mechanisms that underlie NK cell dysregulation after trauma. Restoration of the mTOR phosphorylation capacity along with inhibition of the TGF-βRI signaling in NK cells after severe injury might improve the immune defense against opportunistic infections.

Autoantibody-positive healthy individuals with lower lupus risk display a unique immune endotype

BACKGROUND

Autoimmune diseases comprise a spectrum of illnesses and are on the rise worldwide. Although antinuclear antibodies (ANAs) are detected in many autoimmune diseases, up to 20% of healthy women are ANA-positive (ANA+) and most will never develop clinical symptoms. Furthermore, disease transition is higher among ANA+ African Americans compared with ANA+ European Americans.

OBJECTIVE

We sought to determine the immune features that might define and prevent transition to clinical autoimmunity in ANA+ healthy individuals.

METHODS

We comprehensively phenotyped immune profiles of African Americans and European Americans who are ANA-negative (ANA-) healthy, ANA+ healthy, or have SLE using single cell mass cytometry, next-generation RNA-sequencing, multiplex cytokine profiling, and phospho-signaling analyses.

RESULTS

We found that, compared with both ANA- and ANA+ healthy individuals, patients with SLE of both races displayed T-cell expansion and elevated expression of type I and II interferon pathways. We discovered a unique immune signature that suggests a suppressive immune phenotype and reduced CD11C⁺ autoimmunity-associated B cells in healthy ANA+ European Americans that is absent in their SLE or even healthy ANA- counterparts, or among African American cohorts. In contrast, ANA+ healthy African Americans exhibited elevated expression of T-cell activation markers and higher plasma levels of IL-6 than did healthy ANA+ European Americans.

CONCLUSIONS

We propose that this novel immune signature identified in ANA+ healthy European Americans may protect them from T-cell expansion, heightened activation of interferon pathways, and disease transition.

Differentiation of c-Kit+ CD24+ natural killer cells into myeloid cells in a GATA-2-dependent manner

Myeloid progenitor cells have generally been considered the predominant source of myeloid cells under steady-state conditions. Here we show that NK cells contributed to a myeloid cell lineage pool in naïve and tumor-bearing mice. Using fate tracing of NKp46⁺ cells, we found that myeloid cells could be derived from NK cells. Notably, among mature CD11b⁺ CD27⁺ NK cells, c-Kit⁺ CD24⁺ NK cells were capable of differentiating into a range of myeloid lineages in vitro and produced neutrophils and monocytes in vivo. The differentiation was completely inhibited by NK-stimulating cytokines. In addition to the potential for differentiation into myeloid cells, c-Kit⁺ CD24⁺ NK cells retained NK cell phenotypes and effector functions. Mechanistically, GATA-2 was necessary for the differentiation of c-Kit⁺ CD24⁺ NK cells. Therefore, we discovered that GATA-2-dependent differentiation of c-Kit⁺ CD24⁺ NK cells contributes to myeloid cell development and identified a novel pathway for myeloid lineage commitment under physiological conditions.

KIT as a therapeutic target for non-oncological diseases

KIT is a receptor tyrosine kinase that after binding to its ligand stem cell factor activates signaling cascades linked to biological processes such as proliferation, differentiation, migration and cell survival. Based on studies performed on SCF and/or KIT mutant animals that presented anemia, sterility, and/or pigmentation disorders, KIT signaling was mainly considered to be involved in the regulation of hematopoiesis, gametogenesis, and melanogenesis. More recently, novel animal models and ameliorated cellular and molecular techniques have led to the discovery of a widen repertoire of tissue compartments and functions that are being modulated by KIT. This is the case for the lung, heart, nervous system, gastrointestinal tract, pancreas, kidney, liver, and bone. For this reason, the tyrosine kinase inhibitors that were originally developed for the treatment of hemato-oncological diseases are being currently investigated for the treatment of non-oncological disorders such as asthma, rheumatoid arthritis, and alzheimer's disease, among others. The beneficial effects of some of these tyrosine kinase inhibitors have been proven to depend on KIT inhibition. This review will focus on KIT expression and regulation in healthy and pathologic conditions other than cancer. Moreover, advances in the development of anti-KIT therapies, including tyrosine kinase inhibitors, and their application will be discussed.

OP9 Feeder Cells Are Superior to M2-10B4 Cells for the Generation of Mature and Functional Natural Killer Cells from Umbilical Cord Hematopoietic Progenitors

Adoptive natural killer (NK) cell therapy relies on the acquisition of large numbers of mature and functional NK cells. An option for future immunotherapy treatments is to use large amounts of NK cells derived and differentiated from umbilical cord blood (UCB) CD34⁺ hematopoietic stem cells (HSCs), mainly because UCB is one of the most accessible HSC sources. In our study, we compared the potential of two stromal cell lines, OP9 and M2-10B4, for in vitro generation of mature and functional CD56⁺ NK cells from UCB CD34⁺ HSC. We generated higher number of CD56⁺ NK cells in the presence of the OP9 cell line than when they were generated in the presence of M2-10B4 cells. Furthermore, higher frequency of CD56⁺ NK cells was achieved earlier when cultures were performed with the OP9 cells than with the M2-10B4 cells. Additionally, we studied in detail the maturation stages of CD56⁺ NK cells during the in vitro differentiation process. Our data show that by using both stromal cell lines, CD34⁺ HSC in vitro differentiated into the terminal stages 4–5 of maturation resembled the in vivo differentiation pattern of human NK cells. Higher frequencies of more mature NK cells were reached earlier by using OP9 cell line than M2-10B4 cells. Alternatively, we observed that our in vitro NK cells expressed similar levels of granzyme B and perforin, and there were no significant differences between cultures performed in the presence of OP9 cell line or M2-10B4 cell line. Likewise, degranulation and cytotoxic activity against K562 target cells were very similar in both culture conditions. The results presented here provide an optimal strategy to generate high numbers of mature and functional NK cells in vitro, and point toward the use of the OP9 stromal cell line to accelerate the culture procedure to obtain them. Furthermore, this method could establish the basis for the generation of mature NK cells ready for cancer immunotherapy.

Extranodal NK/T cell lymphoma and aggressive NK cell leukaemia: evidence for their origin on CD56+bright CD16-/+dim NK cells

Mature natural killer (NK) cell neoplasms are classified by the World Health Organization into extranodal NK/T cell lymphoma, nasal type (ENKTL) and aggressive NK cell leukaemia (ANKL). In order to propose their normal NK cell counterparts, we reviewed the literature on the phenotype of the neoplastic NK cells from five series of patients with ENKTL (n = 411) and seven series of patients with ANKL (n = 114) and compared with that of the normal and activated mature CD56 NK cell subsets. The tumour NK cells usually express brightly the CD56 adhesion molecule and CD94 lectin type killer receptor, and have an activation-related (cytoplasmic CD3ε, CD7, CD45RO, HLA-DR) phenotype; in contrast, CD16 and killer immunoglobulin-like receptors are frequently negative, and CD57 expression is almost never observed. These phenotypic features would suggest that ENKTL and ANKL cells do represent the neoplastic counterpart of the mature CD56 NK cells, which undergo activation and malignant transformation after Epstein-Barr virus infection.

Practical NK cell phenotyping and variability in healthy adults

Human natural killer (NK) cells display a wide array of surface and intracellular markers that indicate various states of differentiation and/or levels of effector function. These NK cell subsets exist simultaneously in peripheral blood and may vary among individuals. We examined variety among selected NK cell receptors expressed by NK cells from normal donors, as well as the distribution of select NK cell subsets and NK cell receptor expression over time in several individual donors. Peripheral blood mononuclear cells were evaluated using flow cytometry via fluorochrome-conjugated antibodies against a number of NK cell receptors. Results were analyzed for both mean fluorescence intensity (MFI) and the percent positive cells for each receptor. CD56(bright) and CD56(dim) NK cell subsets were also considered separately, as was variation in receptor expression in NK cell subsets over time in selected individuals. Through this effort, we provide ranges of NK cell surface receptor expression for a local adult population as well as provide insight into intra-individual variation.