In addition, repeated injections of ␣-GalCer or the related glycolipid OCH to apolipoprotein E knockout (apoE ؊/؊ ) mice during the early phase of atherosclerosis significantly enlarged the lesion areas compared with mice injected with vehicle control. However, administering ␣-GalCer to apoE ؊/؊ mice with established lesions did not significantly increase the lesion area but considerably decreased the collagen content. Atherosclerosis development in either AD-fed WT or apoE ؊/؊ mice was associated with the presence of V␣14J␣18 transcripts in the atherosclerotic arterial walls, indicating that NKT cells were recruited to these lesions. Thioglycolate-elicited macrophages pulsed with oxidized low-density lipoproteins expressed enhanced CD1d levels and induced NKT cells to produce interferon-␥, a potentially proatherogenic T-helper 1 (T H 1) cytokine. Collectively, we conclude that NKT cells are proatherogenic in mice. IntroductionAtherosclerosis is an inflammatory vascular disease that involves components of the innate and acquired immune systems. [1][2][3] Several studies have suggested that lymphocytes, which are detected in atherosclerotic lesions in humans and mice, 4,5 play a proatherogenic role. [6][7][8] Recently, the role of distinct lymphocyte subsets in the development of atherosclerosis has been evaluated. For example, emerging evidence indicates that T-helper 1 (T H 1) cells are proatherogenic, 9 whereas T H 2 cells are antiatherogenic. 10,11 These observations are further supported by the finding that T H 1 cytokines (eg,) are important in the progression of atherosclerosis [12][13][14][15] and that, among T H 2 cytokines, IL-10 is antiatherogenic. 16 On the other hand, recent studies have suggested that B cells play a protective role in atherogenesis. 17,18 Natural killer T (NKT) cells are a unique subset of lymphocytes that have surface markers and functions of T cells and NK cells. [19][20][21][22][23] Several characteristics of NKT cells suggest that they may play a role in the atherogenic process. Most NKT cells express an invariant V␣14J␣18 T-cell receptor (TCR)-V␣ chain paired with a restricted set of TCR-V␤ chains. These classical NKT cells recognize lipid antigens presented by the major histocompatibility complex (MHC) class 1-like molecule CD1d, produce copious amounts of IFN-␥ and IL-4 on activation, 22 and constitutively express Fas-ligand. 23 Moreover, NKT cells play a protective role in several autoimmune diseases, infections, and tumor progression/ metastasis. 20 Protective effects of NKT cells and their ligands in autoimmunity are largely attributed to their capacity to promote T H 2 immune responses. 24,25 However, in some situations, NKT cells can contribute to the development of T H 1 immune responses as well. 26 Therefore, it was difficult to predict whether NKT cells would play a proatherogenic or an antiatherogenic role. 2 To date, few studies have investigated the role of CD1d and CD1d-dependent T cells in atherogenesis. CD1d-expressing cells are present in human atherosclerotic...

Background-Macrophage and lymphocyte infiltration in adipose tissue may contribute to the pathogenesis of obesity-mediated metabolic disorders. Natural killer T (NKT) cells, which integrate proinflammatory cytokines, have been demonstrated in the atherosclerotic lesions and in visceral adipose tissue. Objective-To determine whether NKT cells are involved in glucose intolerance and adipose tissue inflammation in diet-induced obese mice. Methods and Results-To determine whether NKT cells are involved in the development of glucose intolerance, male ␤ 2 -microglobulin knockout (KO) mice lacking NKT cells and C57BL/6J (wild-type) mice were fed with a high-fat diet (HFD) for 13 weeks. Body weight and visceral obesity were comparable between wild-type and KO mice. However, macrophage infiltration was reduced in adipose tissue and glucose intolerance was significantly ameliorated in KO mice.To further confirm that NKT cells are involved in these abnormalities, ␣-galactosylceramide, 0.1 g/g body weight, which specifically activates NKT cells, was administered after 13 weeks of HFD feeding. ␣-Galactosylceramide significantly exacerbated glucose intolerance and macrophage infiltration as well as cytokine gene expression in adipose tissue. O besity, specifically visceral obesity, increases the risk for metabolic disorders, such as type 2 diabetes mellitus, dyslipidemia, and hypertension as well as atherosclerotic cardiovascular diseases. Previous studies have demonstrated that the accumulation of macrophages within adipose tissue is well documented in obese individuals and that adipose tissue inflammation plays an important role in the pathogenesis of these metabolic disorders. 1,2 Macrophages are attracted by chemokines, such as monocyte chemoattractant protein 1 (MCP-1), and contribute to local inflammation through the release of other inflammatory cytokines, such as tumor necrosis factor (TNF) ␣. In high-fat diet (HFD)-fed obese mice, it has been shown that infiltration of macrophages into adipose tissue coincides with the occurrence of obesitymediated metabolic disorders. 2 The important role of adipose tissue macrophages in the pathogenesis of metabolic disorders has further been supported by recent data in C-C motif chemokine receptor 2 (CCR2)-deficient mice. 3 The CCR2 Ϫ/Ϫ mice exhibited a reduction in adipose tissue macrophages in association with an improvement of glucose homeostasis and insulin sensitivity. However, the abolished monocyte and macrophage recruitment into peripheral tissue via interaction with MCP-1 could not completely inhibit HFD-mediated metabolic disorders, suggesting that other inflammatory cells may play a role in this context. Wu et al 4 and Rocha et al 5 demonstrated that CD3-positive T lymphocytes are present in human adipose tissue; and regulated upon activation, normal T cell expressed secreted (RANTES), a T-cell-specific chemokine, and its respective receptor CCR5 are expressed in adipose tissue from obese patients. However, the role of other types of lymphocytes in adipose tissue inflam...

The progression of obesity is accompanied by a chronic inflammatory process that involves both innate and acquired immunity. Natural killer T (NKT) cells recognize lipid antigens and are also distributed in adipose tissue. To examine the involvement of NKT cells in the development of obesity, C57BL/6 mice (wild type; WT), and two NKT-cell-deficient strains, Jα18−/− mice that lack the type I subset and CD1d−/− mice that lack both the type I and II subsets, were fed a high fat diet (HFD). CD1d−/− mice gained the least body weight with the least weight in perigonadal and brown adipose tissue as well as in the liver, compared to WT or Jα18−/− mice fed an HFD. Histologically, CD1d−/− mice had significantly smaller adipocytes and developed significantly milder hepatosteatosis than WT or Jα18−/− mice. The number of NK1.1+TCRβ+ cells in adipose tissue increased when WT mice were fed an HFD and were mostly invariant Vα14Jα18-negative. CD11b+ macrophages (Mφ) were another major subset of cells in adipose tissue infiltrates, and they were divided into F4/80high and F4/80low cells. The F4/80low-Mφ subset in adipose tissue was increased in CD1d−/− mice, and this population likely played an anti-inflammatory role. Glucose intolerance and insulin resistance in CD1d−/− mice were not aggravated as in WT or Jα18−/− mice fed an HFD, likely due to a lower grade of inflammation and adiposity. Collectively, our findings provide evidence that type II NKT cells initiate inflammation in the liver and adipose tissue and exacerbate the course of obesity that leads to insulin resistance.

SUMMARYMouse allograft in¯ammatory factor-1 (AIF-1) cDNA was cloned and the AIF-1-speci®c monoclonal antibodies were established to examine its tissue distribution. The mouse AIF-1 was highly conserved among all reported AIF-1 from a variety of species, from invertebrates to mammals, and the cloned cDNA was in good accordance with putative expressed regions of genomic sequences in the mouse major histocompatibility complex (MHC) class III region. The messages of mouse AIF-1 were abundantly expressed in the testis, moderately in the spleen and lymph nodes and slightly in the liver and thymus of normal BALB/c mice. Immunohistological examination revealed that differentiating germ cells in the testis and presumably macrophages in the red pulp of the spleen were positive for AIF-1. To analyse the function of the AIF-1, a macrophage cell line, RAW 264.7, was transfected with mouse AIF-1 cDNA. Upon stimulation with bacterial lipopolysaccharide, the transfectants that overexpressed AIF-1 showed marked morphological changes and produced signi®cantly large amounts of interleukin (IL)-6, IL-10 and IL-12p40 but not IL-12p70 compared with control cells. No difference was noted in production of tumour necrosis factor-a, transforming growth factor-b 1 and IL-1a. These results suggest that AIF-1 plays an important role in cells of a monocyte/macrophage lineage upon stimulation with in¯ammatory stimuli by augmenting particular cytokine production.