Lineage Diversion of T Cell Receptor Transgenic Thymocytes Revealed by Lineage Fate Mapping

Background: The binding of the T cell receptor (TCR) to major histocompatibility complex (MHC) molecules in the thymus determines fates of $TCR\alpha\beta$ lymphocytes that subsequently home to secondary lymphoid tissue. TCR transgenic models have been used to study thymic selection and lineage commitment. Most TCR transgenic mice express the rearranged $TCR\alpha\beta$ prematurely at the double negative stage and abnormal TCRαβ populations of T cells that are not easily detected in non-transgenic mice have been found in secondary lymphoid tissue of TCR transgenic mice. Methodology and Principal Findings: To determine developmental pathways of TCR-transgenic thymocytes, we used Cre-LoxP-mediated fate mapping and show here that premature expression of a transgenic $TCR\alpha\beta$ diverts some developing thymocytes to a developmental pathway which resembles that of gamma delta cells. We found that most peripheral T cells with the HY-TCR in male mice have bypassed the RORγt-positive $CD4^{+}8^{+}$ (double positive, DP) stage to accumulate either as $CD4^{-}8^{-}$ (double negative, DN) or as $CD8\alpha^{+}$ T cells in lymph nodes or gut epithelium. Likewise, DN $TCR\alpha\beta$ cells in lymphoid tissue of female mice were not derived from DP thymocytes. Conclusion: The results further support the hypothesis that the premature expression of the $TCR\alpha\beta$ can divert DN thymocytes into gamma delta lineage cells

Interferon Gamma-Dependent Intestinal Pathology Contributes to the Lethality in Bacterial Superantigen-Induced Toxic Shock Syndrome

Toxic shock syndrome (TSS) caused by the superantigen exotoxins of Staphylococcus aureus and Streptococcus pyogenes is characterized by robust T cell activation, profound elevation in systemic levels of multiple cytokines, including interferon-γ (IFN-γ), followed by multiple organ dysfunction and often death. As IFN-γ possesses pro- as well as anti-inflammatory properties, we delineated its role in the pathogenesis of TSS. Antibody-mediated in vivo neutralization of IFN-γ or targeted disruption of IFN-γ gene conferred significant protection from lethal TSS in HLA-DR3 transgenic mice. Following systemic high dose SEB challenge, whereas the HLA-DR3.IFN-γ+/+ mice became sick and succumbed to TSS, HLA-DR3.IFN-γ−/− mice appeared healthy and were significantly protected from SEB-induced lethality. SEB-induced systemic cytokine storm was significantly blunted in HLA-DR3.IFN-γ−/− transgenic mice. Serum concentrations of several cytokines (IL-4, IL-10, IL-12p40 and IL-17) and chemokines (KC, rantes, eotaxin and MCP-1) were significantly lower in HLA-DR3.IFN-γ−/− transgenic mice. However, SEB-induced T cell expansion in the spleens was unaffected and expansion of SEB-reactive TCR Vβ8+ CD4+ and CD8+ T cells was even more pronounced in HLA-DR3.IFN-γ−/− transgenic mice when compared to HLA-DR3.IFN-γ+/+ mice. A systematic histopathological examination of several vital organs revealed that both HLA-DR3.IFN-γ+/+ and HLA-DR3.IFN-γ−/− transgenic mice displayed comparable severe inflammatory changes in lungs, and liver during TSS. Remarkably, whereas the small intestines from HLA-DR3.IFN-γ+/+ transgenic mice displayed significant pathological changes during TSS, the architecture of small intestines in HLA-DR3.IFN-γ−/− transgenic mice was preserved. In concordance with these histopathological changes, the gut permeability to macromolecules was dramatically increased in HLA-DR3.IFN-γ+/+ but not HLA-DR3.IFN-γ−/− mice during TSS. Overall, IFN-γ seemed to play a lethal role in the immunopathogenesis of TSS by inflicting fatal small bowel pathology. Our study thus identifies the important role for IFN-γ in TSS

Intestinal intraepithelial lymphocyte-enterocyte crosstalk regulates production of bactericidal angiogenin 4 by Paneth cells upon microbial challenge

Antimicrobial proteins influence intestinal microbial ecology and limit proliferation of pathogens, yet the regulation of their expression has only been partially elucidated. Here, we have identified a putative pathway involving epithelial cells and intestinal intraepithelial lymphocytes (iIELs) that leads to antimicrobial protein (AMP) production by Paneth cells. Mice lacking γδ iIELs (TCRδ(-/-)) express significantly reduced levels of the AMP angiogenin 4 (Ang4). These mice were also unable to up-regulate Ang4 production following oral challenge by Salmonella, leading to higher levels of mucosal invasion compared to their wild type counterparts during the first 2 hours post-challenge. The transfer of γδ iIELs from wild type (WT) mice to TCRδ(-/-) mice restored Ang4 production and Salmonella invasion levels were reduced to those obtained in WT mice. The ability to restore Ang4 production in TCRδ(-/-) mice was shown to be restricted to γδ iIELs expressing Vγ7-encoded TCRs. Using a novel intestinal crypt co-culture system we identified a putative pathway of Ang4 production initiated by exposure to Salmonella, intestinal commensals or microbial antigens that induced intestinal epithelial cells to produce cytokines including IL‑23 in a TLR-mediated manner. Exposure of TCR-Vγ7(+) γδ iIELs to IL-23 promoted IL‑22 production, which triggered Paneth cells to secrete Ang4. These findings identify a novel role for γδ iIELs in mucosal defence through sensing immediate epithelial cell cytokine responses and influencing AMP production. This in turn can contribute to the maintenance of intestinal microbial homeostasis and epithelial barrier function, and limit pathogen invasion

Randomized, multi-center trial of two hypo-energetic diets in obese subjects: high- versus low-fat content

Objective:To investigate whether a hypo-energetic low-fat diet is superior to a hypo-energetic high-fat diet for the treatment of obesity.Design:Open-label, 10-week dietary intervention comparing two hypo-energetic (-600 kcal/day) diets with a fat energy percent of 20-25 or 40-45.Subjects:Obese (BMI >/=30 kg/m(2)) adult subjects (n=771), from eight European centers.Measurements:Body weight loss, dropout rates, proportion of subjects who lost more than 10% of initial body weight, blood lipid profile, insulin and glucose.Results:The dietary fat energy percent was 25% in the low-fat group and 40% in the high-fat group (mean difference: 16 (95% confidence interval (CI) 15-17)%). Average weight loss was 6.9 kg in the low-fat group and 6.6 kg in the high-fat group (mean difference: 0.3 (95% CI -0.2 to 0.8) kg). Dropout was 13.6% (n=53) in the low-fat group and 18.3% (n=70) in the high-fat group (P=0.001). Among completers, more subjects lost >10% in the low-fat group than in the high-fat group ((20.8%, n=70) versus (14.7%, n=46), P=0.02). Fasting plasma total, low-density lipoprotein- and high-density lipoprotein-cholesterol decreased in both groups, but more so in the low-fat group than in the high-fat group. Fasting plasma insulin and glucose were lowered equally by both diets.Conclusions:The low-fat diet produced similar mean weight loss as the high-fat diet, but resulted in more subjects losing >10% of initial body weight and fewer dropouts. Both diets produced favorable changes in fasting blood lipids, insulin and glucose.International Journal of Obesity advance online publication, 6 December 2005; doi:10.1038/sj.ijo.0803186

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació