IntroductionHuman V␣24 ϩ V␤11 ϩ natural killer T (NKT) cells are a distinct CD1d-restricted lymphoid subset specifically activated and induced to proliferate by ␣-galactosylceramide (␣-GalCer) (KRN7000) presented by CD1d on antigen-presenting cells (APCs), including dendritic cells (DCs) and monocyte-derived DCs (MoDCs). [1][2][3][4][5] Preclinical murine in vivo and human in vitro data suggest NKT cell activation may be therapeutic for human malignancy. 6,7 NKT cells have direct antitumor cytotoxicity, dependent on and independent of target CD1d expression, 8 and antiproliferative actions 9 that may contribute to clinical antitumor activity.Potentially critical for successful human tumor eradication are secondary immune effects, including cytokine release 9,10 and activation of conventional T cells 11 and NK cells [12][13][14][15][16][17] resulting from the hypothesized pivotal role of NKT cells in bridging, coordinating, and activating innate and acquired immunity. 11 A human clinical study showed that direct intravenous administration of ␣-GalCer results in disappearance of peripheral blood (PB) NKT cells within 24 hours, and with multiple administrations at weekly intervals, NKT cell numbers remain below pretreatment levels. 18 Furthermore, it has been demonstrated in murine models that administration of ␣-GalCer-pulsed DCs has more potent antitumour activities than direct administration of ␣-GalCer alone. 19 In addition to their essential role in NKT cell activation, DCs may have a crucial intermediary role in secondary immune effects of activated NKT cells as the latter alter DC functions, including cytokine production. 20,21 In view of these earlier murine and clinical studies and to confirm the proposed key immune-activating activities of NKT cells, we have undertaken a clinical phase 1 study to determine the effects of ␣-GalCer-pulsed DCs in human subjects. We evaluated clinical and immunologic effects of ␣-GalCer-pulsed MoDCs administered at 2-week intervals to 12 human subjects with metastatic malignancy. Materials and methods Overview of study designThe study was a phase 1, open-labeled clinical study involving 12 patients with metastatic malignancy (Table 1). Subjects received a median of 5 ϫ 10 6 CD1d-expressing immature MoDCs generated from plastic adherent monocytes cultured with interleukin 4 (IL-4) and granulocytemacrophage colony-stimulating factor (GM-CSF). Subjects involved in another of our studies with metastatic malignancy (n ϭ 3) receiving therapy with MoDCs prepared with the use of identical protocols, but with addition of tumor lysate or tumor-specific peptides rather than ␣-GalCer, were used as controls but had less extensive immunologic evaluations than for the study described here. One subject (KS103) received 2 series of treatments with KRN7000-pulsed MoDCs, several months apart, and subsequently (6 months later) a series of treatments with tumor lysate-pulsed MoDCs. Protocols were based on those previously described 22 with our minor modifications, 23 except that 100 ng/mL ␣-GalCe...

Glycolipid-reactive V␣24 ؉ invariant natural killer T (iNKT) cells have been implicated in regulating a variety of immune responses and in the induction of immunologic tolerance. Activation of iNKT cells requires interaction with professional antigen-presenting cells, such as dendritic cells (DCs).We have investigated the capacity of distinct DC subsets to modulate iNKT cell functions. We demonstrate that tolerogenic DCs (tolDCs), generated by treatment of monocyte-derived DC with interleukin (IL)-10, induced regulatory functions in human iNKT cells. tolDCs, compared with immunogenic DCs, had reduced capacity to induce iNKT-cell proliferation, but these cells produced large amounts of IL-10 and acquired an anergic phenotype. These anergic V␣24 ؉ iNKT cells were able to potently inhibit allogeneic CD4 ؉ T-cell proliferation in vitro. Furthermore, the anergic V␣24 ؉ iNKT cells could suppress DC maturation in vitro. We conclude that the interaction of iNKT cells with tolDCs plays an important role in the immune regulatory network, which might be exploited for therapeutic purposes. IntroductionHuman CD1d-restricted invariant natural killer T (iNKT) cells are a unique class of T lymphocytes, which express NK cell receptors and an invariant T-cell receptor (TCR) containing a V␣24-J␣Q ␣-chain. 1 This invariant TCR on iNKT cells recognizes glycolipids, such as ␣-galactosylceramide (␣-GalCer), presented by the CD1d molecule on antigen-presenting cells (APCs), such as dendritic cells (DCs). 2,3 ␣-GalCer potently stimulates iNKT cells to rapidly produce large amounts of T helper type (Th) 1 cytokines, such as interferon (IFN)-␥ and Th2 cytokines such as interleukin-4 (IL-4). 3 Human iNKT cells have been implicated in the regulation of autoimmune responses in various diseases [4][5][6] (ie, type 1 diabetes, 7-9 multiple sclerosis, 10,11 and others 12,13 ) and graft-versus-host disease (GVHD). 14 Patients with autoimmune diseases or GVHD typically have reduced frequency of iNKT cells [7][8][9][10][11][12][13][14] with reduced capacity to produce Th2 cytokines, including IL-4 and IL-10. [7][8][9][10][11] The secretion of Th2 cytokines polarizes naive T cells toward a Th2 response and is thought to shift the balance from a pathogenic Th1 toward a protective Th2 response in Th1-dominant autoimmunity. Thus, iNKT cells can play a regulatory role in the immune response by promoting Th2 responses that are capable of suppressing T cell-mediated autoimmunity. 3 In addition, recent studies have reported that repeated administration of ␣-GalCer to mice can elicit iNKT cells producing IL-4 and IL-10 but not IFN-␥, resulting in prevention of experimental autoimmune diseases in murine models. [15][16][17] Specifically, in the murine system, IL-10 produced by iNKT cells with regulatory functions shifts DCs to IL-10-producing regulatory DCs. These regulatory DCs have been implicated in the induction of regulatory CD4 ϩ T cells that, in turn, suppress the development of autoimmunity in vivo. 17 It has been reported that DCs can influence th...