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CD1d-restricted invariant NKT (iNKT) cells play important regulatory roles in various immune responses, including antitumor immune responses. Previous studies have demonstrated quantitative and qualitative defects in iNKT cells of cancer patients, and these defects are clinically relevant as they are associated with poor prognosis. In this study we demonstrate that defects in the iNKT cell population can, at least in part, be attributed to defective interactions between iNKT cells and CD1d-expressing circulating myeloid dendritic cells (mDC), as mDC of patients with advanced melanoma and renal cell cancer reduced the activation and Th1 cytokine production of healthy donor-derived iNKT cells. Interestingly, this reduced activation of iNKT cells was restricted to patients with low circulating iNKT cell numbers and could be reversed by IL-12 and in part by the neutralization of TGF-beta, but it was further reduced by the neutralization of IL-10 in vitro. Additional experiments revealed discordant roles for TGF-beta and IL-10 on human iNKT cells, because TGF-beta suppressed iNKT cell activation and proliferation and IFN-gamma production while IL-10 was identified as a cytokine involved in stimulating the activation and expansion of iNKT cells that could subsequently suppress NK cell and T cell responses.

Invariant Natural Killer T (iNKT) cells are CD1d restricted innate lymphoid cells with an invariant T cell receptor (TCR) alpha chain gene rearrangement (Valpha24-Jalpha18 in human and Valpha14-Jalpha18 in mouse). iNKT cells play a pivotal role in anti-tumor immune responses via cytokine mediated transactivation of various cells which mediate innate and adaptive immune responses. Here we describe, to our knowledge for the first time, the generation of long-term mouse spleen derived iNKT cell lines. We found that dendritic cells (DC) derived from the D1 line, but not Mf4/4 macrophages, loaded with the artificial iNKT cell ligand alpha-Galactosylceramide (alphaGalCer) could be employed to expand iNKT cells in vitro. Furthermore, exogenously added IL-7, but not IL-2 or IL-15 had a pronounced additive effect on iNKT cell expansion. Using this method up to 10(8) iNKT cells could be obtained from one spleen within 12 to 14 weeks, and cell lines could be continued for up to 24 months. Importantly, the iNKT cell lines had retained the capacity to swiftly secrete substantial amounts of both T helper (Th) 1 and Th2 cytokines upon activation. In conclusion we have generated iNKT cell lines with high yields that can be maintained for up to 24 months, by repeated stimulation using alpha-GalCer loaded D1.DC and IL-7. These in vitro expanded iNKT cells preserved the capacity to swiftly produce both Th1 and Th2 type cytokines and are currently being utilized in pre-clinical adoptive transfer models to identify and optimize the characteristics of therapeutically effective iNKT cells in an anti-tumor setting.

Many human myeloid leukemia-derived cell lines possess the ability to acquire a dendritic cell (DC) phenotype. However, cytokine responsiveness is generally poor, requiring direct manipulation of intracellular signaling mechanisms for differentiation. In contrast, the CD34+ human acute myeloid leukemia cell line MUTZ-3 responds to granulocyte macrophage- colony-stimulating factor (GM-CSF), interleukin 4 (IL-4), and tumor necrosis factor alpha (TNFalpha), cytokines known to be pivotal both in vivo and in vitro for DC generation from monocytes and CD34+ stem cells. In all respects, MUTZ-3 cells behave as the immortalized equivalent of CD34+ DC precursors. Upon stimulation with specific cytokine cocktails, they acquire a phenotype consistent with either interstitial- or Langerhans-like DCs and upon maturation (mDC), express CD83. MUTZ-3 DC display the full range of functional antigen processing and presentation pathways. These findings demonstrate the unique suitability of MUTZ-3 cells as an unlimited source of CD34+ DC progenitors for the study of cytokine-induced DC differentiation.

The efficacy of autologous (αβ) T-cell--based treatment strategies in chronic lymphocytic leukemia (CLL) has been modest. The Vγ9Vδ2-T cell subset consists of cytotoxic T lymphocytes with potent antilymphoma activity via a major histocompatibility complex--independent mechanism. We studied whether Vγ9Vδ2 cells can be exploited as autologous effector lymphocytes in CLL. Healthy control Vγ9Vδ2 cells were activated by and had potent cytolytic activity against CLL cells. However, CLL-derived Vγ9Vδ2 cells proved dysfunctional with respect to effector cytokine production and degranulation, despite an increased frequency of the effector-type subset. Consequently, cytotoxicity against malignant B cells was hampered. A comparable dysfunctional phenotype was observed in healthy Vγ9Vδ2 cells after coculture with CLL cells, indicating a leukemia-induced mechanism. Gene-expression profiling implicated alterations in synapse formation as a conceivable contributor to compromised Vγ9Vδ2--cell function in CLL patients. Dysfunction of Vγ9Vδ2 cells was fully reversible upon activation with autologous monocyte-derived dendritic cells (moDCs). moDC activation resulted in efficient expansion and predominantly yielded Vγ9Vδ2 cells with a memory phenotype. Furthermore, ibrutinib treatment promoted an antitumor T helper 1 (TH1) phenotype in Vγ9Vδ2 cells, and we demonstrated binding of ibrutinib to IL-2-inducible kinase (ITK) in Vγ9Vδ2 cells. Taken together, CLL-mediated dysfunction of autologous Vγ9Vδ2 cells is fully reversible, resulting in potent cytotoxicity toward CLL cells. Our data support the potential use of Vγ9Vδ2 cells as effector T cells in CLL immunotherapy and favor further exploration of combining Vγ9Vδ2-cell--based therapy with ibrutinib. [ABSTRACT FROM AUTHOR]

Aminobisphosphonates (NBP) are used for treatment of metastatic bone disease. Frequently, patients undergoing NBP-treatment experience side-effects, known as acute phase response (APR), resulting from cytokine production by Vγ9Vδ2-T cells. As opposed to NBP, statins reduce intracellular phosphoantigen levels and prevent NBP-induced Vγ9Vδ2-T cell activation in vitro . We conducted a pilot study in patients with (bone-)metastasized malignancies receiving NBP-treatment and evaluated the phenotype and function of circulating Vγ9Vδ2-T cells in vivo and the effects of statins on Vγ9Vδ2-T cell responses and the associated APR. We observed reduced expression of perforin, granzyme B and HLA-DR on Vγ9Vδ2-T cells in patients treated with NBP and statins. However, statins could not prevent NBP-induced changes in circulating Vγ9Vδ2-T cell numbers or production of IFNγ and TNFα. Consistent with this, simvastatin could not prevent the occurrence of APR upon NBP-infusion. These observations call for the exploration of alternative strategies to prevent collateral APR upon NBP treatment. [ABSTRACT FROM AUTHOR]

Vγ9Vδ2 T cell activation plays an important role in antitumor and antimicrobial immune responses. However, there are conditions in which Vγ9Vδ2 T cell activation can be considered inappropriate for the host. Patients treated with aminobisphosphonates for hypercalcemia or metastatic bone disease often present with a debilitating acute phase response as a result of Vγ9Vδ2 T cell activation. To date, no agents are available that can clinically inhibit Vγ9Vδ2 T cell activation. In this study, we describe the identification of a single domain Ab fragment directed to the TCR of Vγ9Vδ2 T cells with neutralizing properties. This variable domain of an H chain-only Ab (VHH or nanobody) significantly inhibited both phosphoantigen-dependent and -independent activation of Vγ9Vδ2 T cells and, importantly, strongly reduced the production of inflammatory cytokines upon stimulation with aminobisphosphonate-treated cells. Additionally, in silico modeling suggests that the neutralizing VHH binds the same residues on the Vγ9Vδ2 TCR as the Vγ9Vδ2 T cell Ag-presenting transmembrane protein butyrophilin 3A1, providing information on critical residues involved in this interaction. The neutralizing Vγ9Vδ2 TCR VHH identified in this study might provide a novel approach to inhibit the unintentional Vγ9Vδ2 T cell activation as a consequence of aminobisphosphonate administration. [ABSTRACT FROM AUTHOR]

Hepatitis C virus (HCV)-specific T-cell responses are rarely detected in peripheral blood, especially in the presence of human immunodeficiency virus (HIV) coinfection. Based on recent evidence that T-regulatory cells may be increased in chronic HCV, we hypothesized that functional blockade of regulatory cells could raise HCV-specific responses and might be differentially regulated in the setting of HIV coinfection. Three groups of subjects were studied: HCV monoinfected, HCV-HIV coinfected, and healthy controls. Frequencies of peripheral T cells specific for peptides derived from HCV core, HIV type 1 p24, and recall antigens were analyzed by gamma interferon (IFN-γ) enzyme-linked immunospot assay. HCV-specific T-cell responses were very weak in groups with HCV and HCV-HIV infections. Addition of blocking antibodies against transforming growth factor β1 (TGF-β1), -2, and -3 and interleukin-10 specifically increased the HCV-specific T-cell responses in both infected groups; however, this increase was attenuated in the group with HCV-HIV coinfection compared to HCV infection alone. No increase in recall antigen- or HIV-specific responses was observed. Flow cytometric sorter analysis demonstrated that regulatory-associated cytokines were produced by HCV-specific CD3+CD8+CD25- cells. Enhancement of the IFN-γ effect was observed for both CD4 and CD8 T cells and was mediated primarily by TGF-β1, -2, and -3 neutralization. In conclusion, blockade of TGF-β secretion could enhance peripheral HCV-specific T-cell responses even in the presence of HIV coinfection. [ABSTRACT FROM AUTHOR]