Activation of the innate immune system in obesity is a risk factor for the development of type 2 diabetes. The aim of the current study was to investigate the notion that increased numbers of macrophages exist in the islets of type 2 diabetes patients and that this may be explained by a dysregulation of islet-derived inflammatory factors. Increased islet-associated immune cells were observed in human type 2 diabetic patients, high-fat-fed C57BL/6J mice, the GK rat, and the db/db mouse. When cultured islets were exposed to a type 2 diabetic milieu or when islets were isolated from high-fat-fed mice, increased isletderived inflammatory factors were produced and released, including interleukin (IL)-6, IL-8, chemokine KC, granulocyte colony-stimulating factor, and macrophage inflammatory protein 1␣. The specificity of this response was investigated by direct comparison to nonislet pancreatic tissue and ␤-cell lines and was not mimicked by the induction of islet cell death. Further, this inflammatory response was found to be biologically functional, as conditioned medium from human islets exposed to a type 2 diabetic milieu could induce increased migration of monocytes and neutrophils. This migration was blocked by IL-8 neutralization, and IL-8 was localized to the human pancreatic ␣-cell. Therefore, islet-derived inflammatory factors are regulated by a type 2 diabetic milieu and may contribute to the macrophage infiltration of pancreatic islets that we observe in type 2 diabetes. Diabetes 56:2356-2370, 2007 A ctivation of the innate immune system has long been reported in obesity, insulin resistance, and type 2 diabetics and is characterized by increased circulating levels of acute-phase proteins and of cytokines and chemokines (1-5). However, the notion that excess circulating nutrients may stimulate the ␤-cell to produce chemokines remains unexplored, and immune cell infiltration has not been shown in islets of type 2 diabetic patients.One of the most classical chemotactic agents in immunology is the CXC family chemokine, interleukin (IL)-8 (CXCL8) (6). IL-8 is produced by leukocytes, fibroblasts, and endothelial and epithelial cells and is commonly associated with infections, graft rejection, allergy, asthma, cancer, and atherosclerosis. In addition to its effect on neutrophils, the chemotactic effect of IL-8 also is important in mediating monocyte migration (7-9). The rodent does not express IL-8. Instead, the rodent functional homolog of IL-8 is thought to be chemokine KC (CXCL1, or Gro-␣ in the rat), which also has been reported to induce granulocyte and monocyte migration (9). Chemokine KC is thought to be an ortholog of human CXCL1. Circulating levels of IL-8 are elevated in type 2 diabetic individuals (10,11), in whom IL-8 has been implicated in systemic insulin resistance and atherosclerosis (12,13).Thus, we hypothesized that pancreatic islets in type 2 diabetes are characterized by increased macrophage infiltration and that a type 2 diabetic milieu could promote chemokine production in pancreatic islets. ...

In acute experimental autoimmune encephalomyelitis (EAE), demyelination is induced by myelin‐specific CD4+ T lymphocytes and myelin‐specific antibodies. Recovery from the disease is initiated by cytokines which suppress T cell expansion and the production of myelin‐toxic molecules by macrophages. Th2/3 cell‐derived signals may also be involved in central nervous system (CNS) repair. Remyelination is thought to be initiated by the recruitment and differentiation of oligodendrocyte precursor cells (OPC) in demyelinated CNS lesions. Here, we report that unlike Th1 cytokines (TNF‐α, IFN‐γ), the Th2/3 cytokine TGF‐β induces primary microglia from C57BL/6 mice to secrete a chemotactic factor for primary OPC. We identified this factor to be the hepatocyte growth factor (HGF). Our studies show that TGF‐β‐1‐2‐3 as well as IFN‐β induce HGF secretion by microglia and that antibodies to the HGF receptor c‐Met abrogate OPC chemotaxis induced by TGF‐β2‐treated microglia. In addition we show spinal cord lesions in EAE induced in SJL/J mice to contain both OPC and HGF producing macrophages in the recovery phase, but not in the acute stage of disease. Taken these findings, TGF‐β may play a pivotal role in remyelination by inducing microglia to release HGF which is both a chemotactic and differentiation factor for OPC.

Dendritic cells (DC) are unique in their ability to prime naive T cells and initiate adaptive immunity. In recent years, DC were identified in the inflamed central nervous system (CNS), but their role in the initiation or regulation of the tissue specific immune response is unknown. As shown here, DC isolated from mice with experimental autoimmune encephalomyelitis (EAE) exhibit a maturational phenotype similar to immature bone marrow-derived DC or splenic DC as characterized by intermediate surface MHC class II and low expression of the costimulatory molecule CD80. However, they are unable to prime naive T cells. Moreover, they inhibit T cell proliferation stimulated by mature bone marrow-derived DC. TGF g , IL-10 and TRAIL were found to significantly contribute to the CNS-DC-mediated inhibition of allo-T cell proliferation. Thus CNS-DC may be the key responsibles for maintaining immune privilege within the inflamed CNS.

F-fluoro-2-deoxyglucose (FDG) are used in the diagnosis of brain tumours. The aim of this study was threefold: (a) to assess the uptake of the different tracers in the F98 rat glioma, (b) to evaluate the impact of blood-brain barrier (BBB) disruption and microvessel density (MVD) on tracer uptake and (c) to compare the uptake in the tumours to that in the radiation injuries (induced by proton irradiation of healthy rats) of our previous study. Methods: F98 gliomas were induced in 26 rats. The uptake of FET, FCH and FDG was measured using autoradiography and correlated with histology, disruption of the BBB and MVD. Results: The mean FET, FCH and FDG standardised uptake values (SUVs) in the tumour and the contralateral normal cortex (in parentheses) were 4.19±0.86 (1.32± 0.26), 2.98± 0.58 (0.51±0.11) and 11.02±3.84 (4.76±1.77) respectively. MVD was significantly correlated only with FCH uptake. There was a trend towards a negative correlation between the degree of BBB disruption and FCH uptake and a trend towards a positive correlation with FET uptake. The ratio of the uptake in tumours to that in the radiation injuries was 1.97 (FCH), 2.71 (FET) and 2.37 (FDG). Conclusion: MVD displayed a significant effect only on FCH uptake. The degree of BBB disruption seems to affect the accumulation of FET and FCH, but not FDG. Mean tumour uptake for all tracers was significantly higher than the accumulation in radiation injuries.

Gliomas localized within the CNS are generally not rejected by the immune system despite being immunogenic. This failure of the immune system has been associated both with glioma-derived immunosuppressive molecules and the immune-privileged state of the CNS. However, the relative contribution of tumor location to the glioma-mediated immunosuppression, as well as the immune mechanisms involved in the failure of glioma rejection are not fully defined. We report here that syngeneic GL261 gliomas growing either intracranially or subcutaneously in mice are infiltrated by DC and T cells. However, only subcutaneous gliomas elicit an effective anti-tumor immune response. In contrast to DC infiltrating subcutaneously grown GL261 gliomas, tumor-infiltrating DC from intracranial gliomas do not activate antigen-dependent T-cell proliferation in vitro. In addition, brain-localized GL261 gliomas are characterized by significantly higher numbers of Foxp3 1 Treg and higher levels of TGF-b1 mRNA and protein expression when compared with GL261 gliomas in the skin. Our data show that gliomas in the CNS, but not in the skin, give rise to TGF-b production and accumulation of both Treg and functionally impaired DC. Thus, not the tumor itself, but its location dictates the efficiency of the antitumor immune response.Key words: DC . Immune privilege . Treg . Tumor immunity Supporting Information available online IntroductionMalignant gliomas, especially the most frequent and aggressive form known as glioblastoma multiforme, are among the most fatal types of tumors. The best standard of care for glioblastoma multiforme, consisting of surgery followed by radiotherapy and chemotherapy with temozolomide, is associated with a median overall survival of 14.6 months following diagnosis [1]. Gliomas have been shown to result in reduced peripheral T-cell responses [2], down-modulated function of circulating APC [3] and particularly to suppressed maturation of peripheral DC [4]. In addition, the localization of the glioma within the immune-privileged CNS, combined with the production of tumorderived immunosuppressive molecules including , , VEGF [9] and prostaglandins [10], is suggested to account for the absence of a successful anti-tumor immune à These authors contributed equally to this work. response. As a consequence, glioma patients fail to generate an effective immune response against the intracranially growing tumors. Although it occurs rarely, gliomas are able to metastasize to locations outside of the brain [11]. The low frequency of peripheral glioma metastases might be due to an efficient recognition of tumor cells outside of the CNS. Gliomas express tumor-associated antigens such as ER-2, gp100, and MAGE-1, which can be recognized by cytotoxic T lymphocyte clones [12]. Furthermore, T-cell clonal expansion has been detected in glioma patients [13] and vaccination of patients with autologous tumor lysate-pulsed DC or autologous tumor peptide-pulsed DC [14] can elicit tumor-specific T-cell responses and infiltration of cytotoxic and me...