In humans, NK cells are mainly identified by the surface expression levels of CD56 and CD16, which differentiate between five functionally different NK cell subsets. However, nowadays NK cells are ...considered as a more heterogeneous population formed by various subsets differing in function, surface phenotype, and anatomic localization. In human CMV- and hantaviruses-infected subjects, an increased frequency of a NKG2A
CD57
NKG2C
NK cell subset has been observed, while the phenotype of the NK cell subpopulation associated with cancer may vary according to the specific kind of tumor and its anatomical location. The healthy human lymph nodes contain mainly the CD56
NK cell subset while in melanoma metastatic lymph nodes the CD56
CD57
KIR
CCR7
NK cell subpopulation prevails. The five NK cell subpopulations are found in breast cancer patients, where they differ for expression pattern of chemokine receptors, maturation stage, functional capabilities. In pregnancy, uterine NK cells show a prevalence of the CD56
CD16
NK cell compartment, whose activity is influenced by KIRs repertoire. This NK cell subset's super specialization could be explained by (i) the expansion of single mature CD56
clones, (ii) the recruitment and maturation of CD56
NK cells through specific stimuli, and (iii) the
development of tumor-resident NK cells from tissue-resident CD56
NK cells independently of the circulating NK cell compartment. This new and unexpected biological feature of the NK cell compartment could be an important source of new biomarkers to improve patients' diagnosis.
NK cell-mediated cytotoxicity is regulated by both triggering and inhibitory signals. The interaction between MHC class I molecules expressed on target cells and specific MHC class I-binding ...receptors expressed by NK cells generally leads to inhibition of lysis. We have shown recently that CD80 (B7-1) in mice and CD40 in humans trigger NK cell-mediated cytotoxicity in vitro. In the present study, we show that murine CD40 and CD86 (B7-2) trigger murine NK cell-mediated cytotoxicity in vitro when expressed on tumor cells. Preincubation of the transfected cell lines with anti-CD40 F(ab')2 fragments or cytolytic T lymphocyte-associated Ag-4-Ig (CTLA-4-Ig) before the cytotoxic assay abolished the triggering effect. Furthermore, radiolabeled CD40- and B7-2-expressing cells were rapidly eliminated in vivo in an NK cell-dependent manner. NK cells from CD40 ligand (CD40L)-/- or CD28-/- mice were triggered by tumor cells transfected with CD40 and B7-2, respectively, and these transfectants were rapidly eliminated in vivo when inoculated into CD40L-/- and CD28-/- mice. This suggests that the CD40 and B7-2 molecules can interact with receptors on NK cells other than CD40L and CD28, respectively, and that these may account for some of the reactivities observed in the present study. Collectively, these data demonstrate that 1) costimulatory molecules, other than B7-1, can modulate NK cell responses in vitro, 2) they can also affect NK cell-dependent responses in vivo, and 3) parts of these reactions are independent of CD28 and CD40L.
The role of natural killer (NK) cells in multiple myeloma is not fully understood. Here, NK susceptibility of myeloma cells derived from distinct disease stages was evaluated in relation to major ...histocompatibility complex (MHC) class I, MHC class I chain-related protein A (MICA), MHC class I chain-related protein B (MICB), and UL16 binding protein (ULBP) expression. MHC class I molecules were hardly detectable on bone marrow cells of early-stage myeloma, while late-stage pleural effusion-derived cell lines showed a strong MHC class I expression. Conversely, a high MICA level was found on bone marrow myeloma cells, while it was low or not measurable on pleural effusion myeloma cells. The reciprocal surface expression of these molecules on bone marrow- and pleural effusion-derived cell was confirmed at mRNA levels. While bone marrow-derived myeloma cells were readily recognized by NK cells, pleural effusion-derived lines were resistant. NK protection of pleural effusion cells was MHC class I dependent. Receptor blocking experiments demonstrated that natural cytotoxicity receptor (NCR) and NK receptor member D of the lectinlike receptor family (NKG2D) were the key NK activating receptors for bone marrow-derived myeloma cell recognition. In ex vivo experiments patient's autologous fresh NK cells recognized bone marrow-derived myeloma cells. Our data support the hypothesis that NK cell cytotoxicity could sculpture myeloma and represents an important immune effector mechanism in controlling its intramedullary stages. (Blood. 2005;105:251-258)
Abstract
Background
Inflammatory bowel disease (IBD) is due to the interaction of genetic and environmental factors that trigger an unbalanced immune response ultimately resulting in the peculiar ...inflammatory reaction. Experimental models of IBD point to a role of T-cell-derived cytokines (Th17) and to SGK1 as mediator of the Th17 switch. We hypothesize that SGK1, a salt inducible kinase, directs lymphocytic behavior and tissue damage.
Methods
Eleven controls and 32 ulcerative colitis (UC) patients were randomized according to endoscopic Mayo score. Mucosal biopsies from different intestinal tracts were analyzed by immunohistochemistry and quantitative real-time polymerase chain reaction to check the expression of disease markers including SGK1. Peripheral blood mononuclear cells (PBMCs) from patients and controls were analyzed by fluorescence-activated cell sorting. Finally, an in vitro cell model was developed to test the hypothesis.
Results
SGK1 mRNA and protein expression in lesional areas of UC patients were lower than in normal peri-lesional areas of the same patients and in normal tissues of healthy controls. SGK1 expression was increased in PBMCs from UC patients, particularly in the CD4+ cell population, enriched in Th17 cells. IL17/IL13 was increased in patients and correlated with SGK1 expression. Genetically engineered Jurkat cells confirmed the effect of SGK1 overexpression on viability of RKO cells.
Conclusions
These observations suggest a pathogenic mechanism whereby SGK1 overexpression in CD4+ T cells induces the secretion of the inflammatory cytokines IL17 and IL13, which downregulate the expression of SGK1 in target tissues. Our data suggest a novel hypothesis in the pathogenesis of UC, integrating colonic epithelial cells and lymphocytes.
The frequent development of drug resistance to targeted therapies in cancer patients has stimulated interest in strategies counteracting resistance. Combining immunotherapies with targeted therapies ...is one such strategy. In this context, we asked whether human NK cells can target melanoma cells that have acquired resistance to selective inhibitors targeting activating mutants of the B‐Raf kinase (BRAF inhibitors, BRAFi). We generated drug‐resistant cell variants in vitro from human BRAF‐mutant melanoma cell lines MEL‐HO, COLO‐38, SK‐MEL‐37, 1520 and from primary melanoma cells freshly isolated from two patients. All drug‐resistant cell variants remained susceptible to lysis by IL‐2‐activated NK cells; and two BRAFi‐resistant lines (BRAFi‐R) became significantly more susceptible to NK‐cell lysis than their parental lines. This was associated with significant HLA class I antigen downregulation and PD‐L1 upregulation on the drug‐resistant lines. Although blocking HLA class I enhanced the extent of lysis of both BRAFi‐R and parental cells to NK‐cell‐mediated lysis, antibody‐mediated inhibition of PD1–PD‐L1 interactions had no detectable effect. HLA class I antigen expression on BRAFi‐R melanoma variants thus appears to play a major role in their susceptibility to NK‐cell cytotoxicity. These findings suggest that NK‐cell‐based immunotherapy may be a viable approach to treat melanoma patients with acquired resistance to BRAF inhibitors.
Abstract
Endothelial cells play an important role in transmission of JEV across the blood brain barrier while fibroblasts are involved in peripheral spread of infection. JEV, a neurotropic flavivirus ...was found to replicate and establish productive infection in human endothelial cell lines leading to production of IFN-β and TNF-α. Expression of HLA-E mRNA and protein showed significant upregulation during JEV infection of the human endothelial cell line, ECV304, human brain microvascular endothelial cells (HBMECs) and a primary human foreskin fibroblast (HFF) cell line. This is the first report to show that the infection of endothelial cells by JEV can result in the release of HLA-E as soluble molecules which is mediated by matrix metalloproteinases. However, HFF cells showed only upregulation of HLA-E on cell surface upon JEV infection. Experiments using inhibitors of MAPK and NF-κB suggest that the release of soluble HLA-E upon JEV infection was dependent on the MAPK pathway but independent of NF-kB. The soluble HLA-E that was released upon JEV infection was functionally active since it inhibited the IL-2 and PMA induced phosphorylation of ERK1/2 in NK cell lines. Inhibition of ERK1/2 phosphorylation has been shown to inhibit cytotoxicity of NK cells by inhibiting mobilization of granzyme granules to immunological synapse. Thus, it is possible that release of soluble HLA-E can have far reaching consequences on activation of NK cells as well as CTLs upon JEV infection.
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