Novel Immunoregulatory Functions of IL-18, an Accomplice of TGF-β1.

TGF-β1 is a pleiotropic factor exerting a strong regulatory role in several cell types, including immune cells. In NK cells it profoundly alters the surface expression of crucial activating and chemokine receptors. To understand which soluble signals might better contrast these effects, we cultured human NK cells in the presence of TGF-β1 and different innate and adaptive cytokines, generally referred as "immunostimulatory".

Molecular Mechanisms Directing Migration and Retention of Natural Killer Cells in Human Tissues.

A large body of data shows that Natural Killer (NK) cells are immune effectors exerting a potent cytolytic activity against tumors and virus infected cells. The discovery and characterization of several inhibitory and activating receptors unveiled most of the mechanisms allowing NK cells to spare healthy cells while selectively attacking abnormal tissues. Nevertheless, the mechanisms ruling NK cell subset recirculation among the different compartments of human body have only lately started to be investigated.

Imatinib and Nilotinib Off-Target Effects on Human NK Cells, Monocytes, and M2 Macrophages.

Tyrosine kinase inhibitors (TKIs) are used in the clinical management of hematological neoplasms. Moreover, in solid tumors such as stage 4 neuroblastomas (NB), imatinib showed benefits that might depend on both on-target and immunological off-target effects. We investigated the effects of imatinib and nilotinib on human NK cells, monocytes, and macrophages.

NK cells and multiple myeloma-associated endothelial cells: molecular interactions and influence of IL-27.

Angiogenesis represents a hallmark of tumor progression in Multiple Myeloma (MM), a still incurable malignancy. Here we analyzed the activity of cytokine-stimulated NK cells against tumor-associated endothelial cells isolated from bone marrow aspirates of MM patients with active disease (MMECs). We show that NK cells activated with optimal doses of IL-15 killed MMECs thanks to the concerted action of multiple activating receptors.

Inhibitory 2B4 contributes to NK cell education and immunological derangements in XLP1 patients.

X-linked lymphoproliferative disease 1 (XLP1) is an inherited immunodeficiency, caused by mutations in SH2D1A encoding Signaling Lymphocyte Activation Molecule (SLAM)-associated protein (SAP). In XLP1, 2B4, upon engagement with CD48, has inhibitory instead of activating function. This causes a selective inability of cytotoxic effectors to kill EBV-infected cells, with dramatic clinical sequelae.

Mesenchymal Stromal Cells Induce Peculiar Alternatively Activated Macrophages Capable of Dampening Both Innate and Adaptive Immune Responses.

Mesenchymal stromal cells (MSCs) support hematopoiesis and exert immunoregulatory activities. Here, we analyzed the functional outcome of the interactions between MSCs and monocytes/macrophages. We showed that MSCs supported the survival of monocytes that underwent differentiation into macrophages, in the presence of macrophage colony-stimulating factor.

PD-L1 expression in metastatic neuroblastoma as an additional mechanism for limiting immune surveillance.

The prognosis of high-risk neuroblastoma (NB) remains poor, although immunotherapies with anti-GD2 antibodies have been reported to provide some benefit. Immunotherapies can be associated with an IFNγ storm that induces in tumor cells the "adaptive immune resistance" characterized by the expression of Programmed Death Ligands (PD-Ls). Tumor cells can also constitutively express PD-Ls in response to oncogenic signaling.

Oxysterol mixture and, in particular, 27-hydroxycholesterol drive M2 polarization of human macrophages.

Macrophages play a crucial role in atherosclerosis progression. Classically activated M1 macrophages have been found in rupture-prone atherosclerotic plaques whereas alternatively activated macrophages, M2, localize in stable plaque. Macrophage accumulation of cholesterol and of its oxidized derivatives (oxysterols) leads to the formation of foam cells, a hallmark of atherosclerotic lesions.

Natural killer cells and neuroblastoma: tumor recognition, escape mechanisms, and possible novel immunotherapeutic approaches.

Neuroblastoma (NB) is the most common extra-cranial solid tumor of childhood and arises from developing sympathetic nervous system. Most primary tumors localize in the abdomen, the adrenal gland, or lumbar sympathetic ganglia. Amplification in tumor cells of MYCN, the major oncogenic driver, patients' age over 18 months, and the presence at diagnosis of a metastatic disease (stage IV, M) identify NB at high risk of treatment failure.

TLR activation of tumor-associated macrophages from ovarian cancer patients triggers cytolytic activity of NK cells.

We analyzed the functional outcome of the interaction between tumor-associated macrophages (TAMs) and natural killer (NK) cells. TAMs from ascites of ovarian cancer patients displayed an alternatively activated functional phenotype (M2) characterized by a remarkably high frequency and surface density of membrane-bound IL-18. Upon TLR engagement, TAMs acquired a classically activated functional phenotype (M1), released immunostimulatory cytokines (IL-12, soluble IL-18), and efficiently triggered the cytolytic activity of NK cells.

Human NK cells and NK receptors.

In early seventies "natural killer (NK) cells", a third lymphocyte subset was discovered that revealed an unexpected ability to kill syngeneic and allogeneic tumor targets, thus emerging as the most potent non-specific cytotoxic cells in both human and mouse. Decades of research revealed the multifaceted nature of these cells. Now we know that NK cells are highly specific cells able to discriminate between self (which is spared) and non-self (which is attacked).

Neuroblastoma-derived TGF-β1 modulates the chemokine receptor repertoire of human resting NK cells.

In this study, we show that neuroblastoma (NB) cell conditioning affects the chemokine receptor repertoire of human resting NK cells. In particular, NB cells upregulated the expression of CXCR4 and CXCR3 in all NK cells and downregulated CX3CR1 in the CD56(dim) subset. On the contrary, the expression of CXCR1 and CCR7 remained unaltered.

M-CSF induces the expression of a membrane-bound form of IL-18 in a subset of human monocytes differentiating in vitro toward macrophages.

IL-18 is a proinflammatory cytokine belonging to the "IL-1 family" that has been shown to play a prominent role in the induction of type 1 immune responses. Here, we show that M-CSF induces the expression of a membrane-bound form of IL-18 (mIL-18) in a subset of human blood monocytes differentiating toward macrophages. While monocytes, DC, and GM-CSF-treated monocytes did not express mIL-18, its expression was detected in approximately 30-40% of M-CSF-primed macrophages differentiating from both CD16(-) and CD16(+) monocytes.

The interaction of human natural killer cells with either unpolarized or polarized macrophages results in different functional outcomes.

The cross-talk among cells of the innate immunity can greatly affect both innate and adaptive responses. Here we analyzed the molecular interactions between human natural killer (NK) cells and autologous macrophages. Activated NK cells killed M0 and M2, whereas M1 macrophages were more resistant to lysis because of their higher expression of HLA class I molecules.

GPR56 as a novel marker identifying the CD56dull CD16+ NK cell subset both in blood stream and in inflamed peripheral tissues.

To define novel human NK cell markers, we generated two mAbs specific for G-protein-coupled receptor 56 (GPR56), a surface glycoprotein that appears to be involved in cell-to-cell and cell-to-matrix interactions. GPR56 has been described in selected normal tissues, and in certain tumors, while, as yet, its expression on leukocytes is unknown. In this study, we show that anti-GPR56 mAbs, among leukocytes, prevalently recognize NK cells.

NK cells recognize and kill human glioblastoma cells with stem cell-like properties.

In this study, cancer cells were isolated from tumor specimens of nine glioblastoma patients. Glioblastoma cells, cultured under suitable culture conditions, displayed markers typical of neural stem cells, were capable of partial multilineage differentiation in vitro, and gave origin to infiltrating tumors when orthotopically injected in NOD/SCID mice. These cells, although resistant to freshly isolated NK cells, were highly susceptible to lysis mediated by both allogeneic and autologous IL-2 (or IL-15)-activated NK cells.

Both CD133+ and CD133- medulloblastoma cell lines express ligands for triggering NK receptors and are susceptible to NK-mediated cytotoxicity.

Adoptive cellular immunotherapy has been proposed as an additional treatment of medulloblastoma, an intracranial tumor characterized by a particularly poor prognosis. However, little is known on the ability of the immune system to effectively attack this tumor. In this study, we show that activated human NK cells efficiently kill medulloblastoma cell lines in vitro.

Analysis of natural killer cells isolated from human decidua: Evidence that 2B4 (CD244) functions as an inhibitory receptor and blocks NK-cell function.

While during the first trimester of pregnancy natural killer (NK) cells represent the most abundant lymphocyte population in the decidua, their actual function at this site is still debated. In this study we analyzed NK cells isolated from decidual tissue for their surface phenotype and functional capability. We show that decidual NK (dNK) cells express normal surface levels of certain activating receptors, including NKp46, NKG2D, and 2B4, as well as of killer cell immunoglobulin-like receptors (KIRs) and CD94/NKG2A inhibitory receptor.

IL-12 or IL-4 prime human NK cells to mediate functionally divergent interactions with dendritic cells or tumors.

In the course of inflammatory responses in peripheral tissues, NK cells may be exposed to cytokines such as IL-12 and IL-4 released by other cell types that may influence their functional activities. In the present study we comparatively analyzed purified human peripheral blood NK cells that had been exposed to either IL-12 or IL-4 during short (overnight) incubation. We show that although IL-12-cultured NK cells produced abundant IFN-gamma, TNF-alpha, and GM-CSF in response to stimuli acting on the NKp46-activating receptor, IL-4-cultured NK cells did not release detectable levels of these cytokines.

Homophilic interaction of NTBA, a member of the CD2 molecular family: induction of cytotoxicity and cytokine release in human NK cells.

NK-T-B antigen (NTBA) is a CD2 family member that functions as a coreceptor in human NK cell activation. Several receptor/ligand interactions occur between different members of this molecular family. In this study, in order to identify the natural ligand of NTBA, we produced a chimeric protein formed by the NTBA extracellular region fused with the Fc portion of human IgG1 (termed NTBA-Fc*).

Structural, functional, and tissue distribution analysis of human transferrin receptor-2 by murine monoclonal antibodies and a polyclonal antiserum.

Human transferrin receptor-2 (TFR-2) is a protein highly homologous to TFR-1/CD71 and is endowed with the ability to bind transferrin (TF) with low affinity. High levels of TFR-2 mRNA were found in the liver and in erythroid precursors. Mutations affecting the TFR-2 gene led to hemochromatosis type 3, a form of inherited iron overload.