[Show abstract][Hide abstract] ABSTRACT: Hemophagocytic lymphohistiocytosis (HLH) comprises an emerging spectrum of inherited and non-inherited disorders of the immune system characterized by the excessive production of cytokines, including interferon-gamma and interleukins (IL)-2, -6 and -10. The Janus kinases (JAKs) transduce signals initiated following engagement of specific receptors that bind a broad array of cytokines, including those over-produced in HLH. Based on the central role for cytokines in the pathogenesis of HLH, we sought to examine whether the inhibition of JAK function might lessen inflammation in murine models of the disease. Towards this end, we examined the effects of JAK inhibition using a model of primary (inherited) HLH in which perforin-deficient (Prf1(-⁄-)) mice are infected with lymphocytic choriomeningitis virus (LCMV) and secondary (non-inherited) HLH in which C57BL/6 mice receive repeated injections of CpG DNA. In both models, treatment with the JAK1/2 inhibitor ruxolitinib significantly lessened the clinical and laboratory manifestations of HLH, including weight loss, organomegaly, anemia, thrombocytopenia, hyper-cytokinemia and tissue inflammation. Importantly, ruxolitinib treatment also significantly improved the survival of LCMV-infected Prf1(-⁄-) mice. Mechanistic studies revealed that in vivo exposure to ruxolitinib inhibited STAT1-dependent gene expression, limited CD8+ T cell expansion and greatly reduced pro-inflammatory cytokine production, without effecting degranulation and cytotoxic function. Collectively, these findings highlight the JAKs as novel, druggable targets for mitigating the cytokine-driven hyper-inflammation that occurs in HLH. These observations also support the incorporation of JAK inhibitors such as ruxolitinib into future clinical trials for patients with these life-threatening disorders.
[Show abstract][Hide abstract] ABSTRACT: Natural killer T (NKT) cells are innate-like lymphocytes that were first described in the late 1980s. Since their initial description, numerous studies have collectively shed light on their development and effector function. These studies have highlighted the unique requirements for the activation of these lymphocytes and the functional responses that distinguish these cells from other effector lymphocyte populations such as conventional T cells and NK cells. This body of literature suggests that NKT cells play diverse nonredundant roles in a number of disease processes, including the initiation and propagation of airway hyperreactivity, protection against a variety of pathogens, development of autoimmunity, and mediation of allograft responses. In this review, however, we focus on the role of a specific lineage of NKT cells in antitumor immunity. Specifically, we describe the development of invariant NKT (iNKT) cells and the factors that are critical for their acquisition of effector function. Next, we delineate the mechanisms by which iNKT cells influence and modulate the activity of other immune cells to directly or indirectly affect tumor growth. Finally, we review the successes and failures of clinical trials employing iNKT cell-based immunotherapies and explore the future prospects for the use of such strategies.
Full-text · Article · Oct 2015 · Journal of Immunology Research
[Show abstract][Hide abstract] ABSTRACT: Invariant natural killer T (iNKT) cells comprise a lineage of CD1d-restricted glycolipid-reactive T lymphocytes with important roles in host immunity to cancer. iNKT cells indirectly participate in antitumor responses by inducing dendritic cell maturation and producing cytokines that promote tumor clearance by CD8(+) T and NK cells. Although iNKT cells thereby act as potent cellular adjuvants, it is less clear whether they directly control the growth of tumors. To gain insights into the direct contribution of iNKT cells to tumor immune surveillance, we developed in vitro and in vivo systems to selectively examine the antitumor activity of iNKT cells in the absence of other cytolytic effectors. Using the EL4 T-lymphoma cell line as a model, we find that iNKT cells exert robust and specific lysis of tumor cells in vitro in a manner that is differentially-induced by iNKT cell agonists of varying TCR affinities, such as OCH, α-galactosyl ceramide and PBS44. In vitro blockade of CD1d-mediated lipid antigen presentation, disruption of T cell receptor (TCR) signaling, or loss of perforin expression significantly reduce iNKT cell killing. Consistent with these findings, iNKT cell reconstitution of T, B, and NK cell-deficient mice slows EL4 growth in vivo via TCR-CD1d and perforin-dependent mechanisms. Together, these observations establish that iNKT cells are sufficient to control the growth of T-lymphoma in vitro and in vivo. They also suggest that the induction of iNKT cell cytotoxic responses in situ might serve as a more effective strategy to prevent and/or treat CD1d(+) cancers, such as T-lymphoma.
[Show abstract][Hide abstract] ABSTRACT: Although invariant natural killer T (iNKT) cells influence antitumor responses indirectly by secreting cytokines and promoting the cytolytic functions of T and NK cells, we find that iNKT cells mediate direct tumoricidal activity in vitro and significantly inhibit tumor growth in vivo, even in the absence of other cytotoxic lymphocytes.
[Show abstract][Hide abstract] ABSTRACT: Haemophagocytic lymphohistiocytosis (HLH) is a life threatening complication of Epstein–Barr virus (EBV) infection. The anti-CD20 antibody rituximab depletes B cells, leading to improved outcomes for patients with EBV-associated B-lymphoproliferative disorders. To gather data on the use of rituximab in EBV-HLH, we performed a retrospective investigation involving 42 EBV-HLH patients who had received treatment with rituximab-containing regimens. On average, patients received 3 rituximab infusions (range 1–10) at a median dose of 375 mg/m2. In all patients, rituximab was administered with other HLH-directed medications, including steroids, etoposide and/or ciclosporin. Rituximab-containing regimens appeared well tolerated and improved clinical status in 43% of patients. Examination of laboratory data obtained prior to and within 2–4 weeks after the first rituximab dose revealed significant reductions in EBV load (median load pre-rituximab: 114 200 copies/ml, median post-rituximab: 225 copies/ml, P = 0·0001) and serum ferritin levels (median ferritin pre-rituximab: 4260 μg/l, median post-rituximab: 1149 μg/l, P = 0·001). Thus, when combined with conventional HLH-directed therapies, rituximab improves symptoms, reduces viral load and diminishes inflammation. These data support the incorporation of rituximab into future prospective clinical trials for patients with EBV-HLH.
No preview · Article · Aug 2013 · British Journal of Haematology
[Show abstract][Hide abstract] ABSTRACT: The adaptor molecule Signaling Lymphocytic Activation Molecule (SLAM)-associated protein (SAP) plays critical roles during invariant natural killer T (iNKT) cell ontogeny. As a result, SAP-deficient humans and mice lack iNKT cells. The strict developmental requirement for SAP has made it difficult to discern its possible involvement in mature iNKT cell functions. Using temporal Cre recombinase-mediated gene deletion to ablate SAP expression after completion of iNKT cell development, we demonstrate that SAP is essential for T cell receptor (TCR)-induced iNKT cell cytotoxicity against T and B leukemia targets in vitro and iNKT cell-mediated control of T leukemia growth in vivo. These findings are not restricted to the murine system, as siRNA-mediated silencing of SAP in human iNKT cells also significantly impairs TCR-induced cytolysis. Mechanistic studies reveal that iNKT cell killing requires the tyrosine kinase Fyn, a known SAP-binding protein. Furthermore, SAP expression is required within murine and human iNKTs to facilitate interaction of iNKT cells with T cell targets and induce reorientation of the microtubule-organizing center to the immunological synapse (IS). Collectively, these studies highlight a novel and essential role for SAP during iNKT cell cytotoxicity and formation of a functional iNKT cell IS.
[Show abstract][Hide abstract] ABSTRACT: Invariant natural killer T (iNKT) cells are innate-like lymphocytes that mediate protection against specific pathogens and tumors. While iNKT cells contribute significantly to tumor responses, the mechanisms that regulate iNKT cell tumor cytotoxicity remain poorly understood. Using in vitro assays, we find that an NKT cell hybridoma and primary murine NKT cells mount cytotoxic responses against EL4 T lymphoma tumor cells in a manner requiring prolonged interactions between the TCR, CD1d, and specific agonistic glycolipid antigens. Optimal iNKT cell killing of EL4 cells also requires expression of the cytolytic granule constituent perforin, but not FasL, TRAIL, or IFN-γ. Importantly, we observe that iNKT cells are sufficient for perforin-dependent control of EL4 cell growth in vivo. Collectively, these findings enhance our understanding of immune responses to tumors, and suggest ways by which to harness iNKT cell cytotoxicity to improve the cellular immunotherapy of T-lymphomas.
[Show abstract][Hide abstract] ABSTRACT: Hemophagocytic lymphohistiocytosis (HLH) is an immunodysregulatory disorder for which more effective treatments are needed. The macrolide rapamycin has immunosuppressive properties, making it an attractive candidate for controlling the aberrant T cell activation that occurs in HLH. To investigate its therapeutic potential, we used rapamycin to treat Lymphocytic Choriomeningitis Virus (LCMV)-infected perforin-deficient (Prf1(-/-)) mice according to a well-established model of HLH. At the regimens tested, rapamycin did not improve weight loss, splenomegaly, hemophagocytosis, cytopenias, or proinflammatory cytokine production in LCMV-infected Prf1(-/-) animals. Thus, single agent rapamycin appears ineffective in treating the clinical and laboratory manifestations of LCMV-induced HLH.
No preview · Article · Dec 2011 · Pediatric Blood & Cancer
[Show abstract][Hide abstract] ABSTRACT: Invariant natural killer T (iNKT) cells comprise a rare lymphocyte sublineage with phenotypic and functional properties similar to T and NK cells. Akin to conventional αβ T cells, their development occurs primarily in the thymus, where they originate from CD4(+) CD8(+) double positive (DP) progenitors. However, the selection of iNKT cells is unique in that it is mediated by homotypic interactions of DP cells and recognition of glycolipid antigen-CD1d complexes. Additionally, iNKT cells acquire an activated innate-like phenotype during development that allows them to release cytokines rapidly following antigen exposure. Given their hybrid features, it is not surprising that the developmental program of iNKT cells partially overlaps with that of T and NK cells. Several recent reports have provided new and exciting insights into the developmental mechanisms that direct natural killer T (NKT) cell lineage commitment and maturation. In this review, we provide a discussion of the NKT cell developmental program with an emphasis on the signaling mechanisms and transcription factors that influence the ontogeny of this lineage. Continued investigations into the complex interplay of these transcription factors and their relationship with other extracellular and intracellular signaling molecules will undoubtedly provide important clues into the biology of this unusual T-cell lineage.
Full-text · Article · Nov 2010 · Immunological Reviews
[Show abstract][Hide abstract] ABSTRACT: X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterized by the clinical triad of increased susceptibility to primary Epstein-Barr virus (EBV) infection, dysgammaglobulinaemia and lymphoma. Most cases are caused by germline mutations in the SH2D1A gene, which encodes the adaptor molecule Signalling Lymphocytic Activation Molecule (SLAM)-associated protein (SAP). Recently, a subset of patients with an XLP-like phenotype was found to carry mutations in XIAP, the gene encoding the X-linked inhibitor of apoptosis protein (XIAP). Studies of XLP patients and Sap-/- mice reveal that loss of SAP expression impairs immune cell activities, such as natural killer and CD8+ T cell cytotoxicity, T cell cytokine production, activation-induced cell death, germinal centre formation and natural killer T cell development. Efforts to dissect the diverse roles of SAP and XIAP are enhancing our understanding of immune cell biology and defining how genetic defects in these molecules predispose to EBV-specific as well as more general cellular and humoral immune dysfunction. These studies are also highlighting critical signalling pathways that might be amenable to pharmacological targeting to improve the treatment of XLP and other disorders associated with impaired antiviral and antitumour immunity.
Full-text · Article · Nov 2010 · British Journal of Haematology