Murine Vα14 natural killer T (NKT) cells are thought to play a crucial role in various immune responses, including infectious, allergic, and autoimmune diseases. Because Vα14 NKT cells produce large amounts of both interleukin (IL)-4 and interferon (IFN)-γ upon in vivo stimulation with a specific ligand, α-galactosylceramide (α-GalCer), or after treatment with anti-CD3 antibody, a regulatory role on helper T (Th) cell differentiation has been proposed for these cells. However, the identity of the cytokine produced by Vα14 NKT cells that play a dominant role on the Th cell differentiation still remains controversial. Here, we demonstrate by using Vα14 NKT-deficient mice that Vα14 NKT cells are dispensable for the induction of antigen-specific immunoglobulin (Ig)E responses induced by ovalbumin immunization or Nippostrongylus brasiliensis infection. However, upon in vivo activation with α-GalCer, Vα14 NKT cells are found to suppress antigen-specific IgE production. The suppression appeared to be IgE specific, and was not detected in either Vα14 NKT– or IFN-γ–deficient mice. Consistent with these results, we also found that ligand-activated Vα14 NKT cells inhibited Th2 cell differentiation in an in vitro induction culture system. Thus, it is likely that activated Vα14 NKT cells exert a potent inhibitory effect on Th2 cell differentiation and subsequent IgE production by producing a large amount of IFN-γ. In marked contrast, our studies have revealed that IL-4 produced by Vα14 NKT cells has only a minor effect on Th2 cell differentiation.

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A unique lymphocyte lineage, the Vα14 NKT cells, expresses both NK1.1 and an invariant antigen receptor encoded by Vα14 and Jα281 gene segments. Vα14 NKT cells play crucial roles in various immune responses, including autoimmune diseases, allergic reactions and anti‐tumor immunity. Vα14 NKT cells were demonstrated to be essential for anti‐tumor effect of IL‐12 in vivo. Here, we report that adoptive transfer of IL‐12‐activated Vα14 NKT cells prevents hepatic metastasis of B16 melanoma. The injection of large amounts of IL‐2, IL‐4, and IFN‐γ, which are cytokines produced by activated Vα14 NKT cells, exhibited no significant inhibition of the metastasis of this melanoma. The cells prepared from the liver of IL‐12‐injected mice expressed a potent cytotoxic activity on B16 melanoma cells in vitro. Although the adoptive transfer of IL‐12‐activated Vα14 NKT cells prevents hepatic metastasis of B16 melanoma, activated NK cells from IL‐12‐injected RAG‐1−/− mice failed to inhibit the metastasis of this melanoma. Thus, the anti‐tumor effect of IL‐12 can be replaced by adoptive transfer of IL‐12‐activated Vα14 NKT cells but not by IL‐12‐activated NK cells, suggesting a minor role of NK cells for the IL‐12‐mediated anti‐tumor effect in this experimental system. Moreover, our studies have suggested the involvement of direct cytotoxic mechanisms rather than cytokine‐mediated immune responses at the effector phase of the Vα14 NKT cell‐mediated anti‐tumor activity. © 2001 Wiley‐Liss, Inc.

A distance cartogram is a diagram that visualizes the proximity indices between points in a network, such as time-distances between cities. The Euclidean distances between the points on the distance cartogram represent the given proximity indices. This is a useful visualization tool for the level of service of transport, e.g. difference in the level of service between regions or points in a network and its improvement in the course of time. The two previously proposed methods-multidimensional scaling (MDS) and network time-space mappinghave certain advantages and disadvantages. However, we observe that these methods are essentially the same, and the merits of both these methods can be combined to formulate a generalized solution. In this study, we first formulate the time-space mapping problem, which includes the key features of both of the above stated methods, and propose a generalized solution. We then apply this solution to the time-distances of Japan's railway networks to confirm its applicability.

Murine NKT cells can recognize alpha-galactosylceramide (alpha-GalCer) in the context of a class Ib CD1d molecule. Here we show that alpha-GalCer can selectively activate freshly isolated human Valpha24(+)Vbeta11(+) cells, functionally defining the human NKT cells. The naive human NKT cell repertoire consisted of cells expressing an invariant Valpha24JalphaQ chain and a diverse array of beta chains derived from a single Vbeta11 gene segment. Stimulation with alpha-GalCer expanded a polyclonal subset of the human NKT cell repertoire carrying a novel complementarity-determining region (CDR) 3beta consensus motif that may directly interact with the sugar moiety of alpha-GalCer. Our data suggest that certain redundancy is allowed for CDR3beta of NKT antigen receptor to interact with the ligand and provide a first clue to understand the novel protein-carbohydrate interaction mechanisms.

A novel lymphocyte, NKT cells bearing an invariant V(alpha)14 antigen receptor, specifically recognizes alpha-galactosylceramide (alpha-GalCer) exclusively presented by mouse CD1d (mCD1d). However, the precise molecular interaction remains unclear. For the basis of functional analyses, a docking model of alpha-GalCer with the crystal structure of mCD1d was constructed. Possible residues involved in the alpha-GalCer--mCD1d interaction were found to be Arg79, Glu83 and Asp80 for carbohydrate recognition, and Asp153 for interaction with the amide group on the fatty acyl chain. The alpha-GalCer-presenting ability of various transfectants expressing mutant mCD1d was completely abrogated if a single amino acid mutation was induced at positions 79, 80, 83 or 153, suggesting that the polar amino acids above the F' pocket are crucial for alpha-GalCer presentation to activate V(alpha)14 NKT cells. The possibility that Glu83 is a contact site for the NKT cell receptor is also discussed.

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NKT cells, a novel murine lymphoid lineage bearing an invariant T cell receptor encoded by Vα14 and Jα281 gene segments, recognize a specific ligand glycolipid, α‐galactosylceramide (α‐GalCer) in a CDld‐dependent manner. Recent research has revealed that activated Vα14 NKT cells have dramatic antitumor effects against a wide variety of tumor cell lines in vivo and in vitro. Here, we demonstrate strong in vivo antitumor effects brought about by treatment with α‐GalCer‐pulsed dendritic cells in comparison with in vitro‐activated Vα14 NKT cells. Furthermore, we show a significant expansion of endogenous Vα14 NKT cells in the lung following the administration of α‐GalCer‐pulsed dendritic cells. The feasibility of immunotherapy with α‐GalCer‐pulsed dendritic cells is discussed.