Richard A. Flavell

Bio: Richard A. Flavell is an academic researcher from Yale University. The author has contributed to research in topics: Immune system & T cell. The author has an hindex of 231, co-authored 1328 publications receiving 205119 citations. Previous affiliations of Richard A. Flavell include National Institute for Medical Research & University of Michigan.

CD4+CD25+ T regulatory cells control anti-islet CD8+ T cells through TGF-β–TGF-β receptor interactions in type 1 diabetes

Abstract: Pancreatic lymph node-derived CD4+CD25+ T regulatory (Treg) cells inhibit in situ differentiation of islet-reactive CD8+ T cells into cytotoxic T lymphocytes, thereby preventing diabetes progression. The mechanism by which these Treg cells suppress anti-islet CD8+ T cells is unknown. Here, we show by using a CD8+ T cell-mediated model of type 1 diabetes that transforming growth factor (TGF)-β–TGF-β receptor signals are critical for CD4+CD25+ Treg cell regulation of autoreactive islet-specific cytotoxic T lymphocytes. Transgenic expression of tumor necrosis factor α from birth to 25 days of age in the islets of B6 mice that constitutively express CD80 on their β cells results in accumulation of CD4+CD25+TGF-β+ cells exclusively in the islets and pancreatic lymph nodes, which delays diabetes progression. In contrast, expression of tumor necrosis factor α until 28 days of age prevents islet accumulation of CD4+CD25+TGF-β+ Treg cells, resulting in acceleration to diabetes. Furthermore, adoptive transfer experiments demonstrated that CD4+CD25+ Treg cells could not control naive or activated isletreactive CD8+ T cells bearing a dominant negative TGF-β receptor type II. Our data demonstrate that, in vivo, TGF-β signaling in CD8+ T cells is critical for CD4+CD25+ Treg cell suppression of isletreactive CD8+ T cells in type 1 diabetes.

Combination delivery of TGF-β inhibitor and IL-2 by nanoscale liposomal polymeric gels enhances tumour immunotherapy

Abstract: The tumour microenvironment thwarts conventional immunotherapy through multiple immunologic mechanisms, such as the secretion of the transforming growth factor-β (TGF-β), which stunts local tumour immune responses. Therefore, high doses of interleukin-2 (IL-2), a conventional cytokine for metastatic melanoma, induces only limited responses. To overcome the immunoinhibitory nature of the tumour microenvironment, we developed nanoscale liposomal polymeric gels (nanolipogels; nLGs) of drug-complexed cyclodextrins and cytokine-encapsulating biodegradable polymers that can deliver small hydrophobic molecular inhibitors and water-soluble protein cytokines in a sustained fashion to the tumour microenvironment. nLGs releasing TGF-β inhibitor and IL-2 significantly delayed tumour growth, increased survival of tumour-bearing mice, and increased the activity of natural killer cells and of intratumoral-activated CD8(+) T-cell infiltration. We demonstrate that the efficacy of nLGs in tumour immunotherapy results from a crucial mechanism involving activation of both innate and adaptive immune responses.

Requirement for CD154 in the progression of atherosclerosis.

Abstract: Atherosclerosis is a systemic disease of the large arteries, and activation of inflammatory pathways is important in its pathogenesis1. Increasing evidence supports the importance of CD40–CD154 interactions in atherosclerosis2,3, interactions originally known to be essential in major immune reactions4 and autoimmune diseases5. CD40 is present on atheroma-derived cells in vitro and in human atheromata in situ6. Ligation of CD40 on atheroma-associated cells in vitro activates the production of chemokines6, cytokines6, matrix metalloproteinases7,8, adhesion molecules9,10 and tissue factor7, substances responsible for lesion progression and plaque destabilization1. Administration of antibody against CD154 to low-density lipoprotein receptor-deficient mice has been shown to reduce atherosclerosis and decrease T-lymphocyte and macrophage content; however, only initial lesions were studied3. Here, we determined the effect of genetic disruption of CD154 in ApoE–/– mice in both initial and advanced atherosclerotic lesions. Plaque area was reduced 550%. In contrast to previous reports, initial lesion development was not affected. Advanced plaques in CD154–/–ApoE–/– mice had a less-lipid-containing, collagen-rich, stable plaque phenotype, with a reduced T-lymphocyte/macrophage content. These data indicate that CD40–CD154 signaling is important in late atherosclerotic changes, such as lipid core formation and plaque destabilization.

Transforming Growth Factor-β and the Immune Response: Implications for Anticancer Therapy

Abstract: Immune homeostasis is a delicate balance between the immune defense against foreign pathogens and suppression of the immune system to maintain self-tolerance and prevent autoimmune disease. Maintenance of this balance involves several crucial networks of cytokines and various cell types. Among these regulators, transforming growth factor-beta (TGF-beta) is a potent cytokine with diverse effects on hematopoietic cells. Its pivotal function within the immune system is to maintain tolerance via the regulation of lymphocyte proliferation, differentiation, and survival. In addition, TGF-beta controls the initiation and resolution of inflammatory responses through the regulation of chemotaxis and activation of leukocytes in the periphery, including lymphocytes, natural killer cells, dendritic cells, macrophages, mast cells, and granulocytes. Through its pleiotropic effects on these immune cells, TGF-beta prevents the development of autoimmune diseases without compromising immune responses to pathogens. However, overactivation of this pathway can lead to several immunopathologies under physiologic conditions including cancer progression, making it an attractive target for antitumor therapies. This review discusses the biological functions of TGF-beta and its effects on the immune system and addresses how immunosuppression by this cytokine can promote tumorigenesis, providing the rationale for evaluating the immune-enhancing and antitumor effects of inhibiting TGF-beta in cancer patients.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Accurate transcription initiation by RNA polymerase II in a soluble extract from isolated mammalian nuclei

Abstract: We have developed a procedure for preparing extracts from nuclei of human tissue culture cells that directs accurate transcription initiation in vitro from class II promoters. Conditions of extraction and assay have been optimized for maximum activity using the major late promoter of adenovirus 2. The extract also directs accurate transcription initiation from other adenovirus promoters and cellular promoters. The extract also directs accurate transcription initiation from class III promoters (tRNA and Ad 2 VA).

Apoptosis: A Review of Programmed Cell Death

Abstract: The process of programmed cell death, or apoptosis, is generally characterized by distinct morphological characteristics and energy-dependent biochemical mechanisms. Apoptosis is considered a vital component of various processes including normal cell turnover, proper development and functioning of the immune system, hormone-dependent atrophy, embryonic development and chemical-induced cell death. Inappropriate apoptosis (either too little or too much) is a factor in many human conditions including neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. The ability to modulate the life or death of a cell is recognized for its immense therapeutic potential. Therefore, research continues to focus on the elucidation and analysis of the cell cycle machinery and signaling pathways that control cell cycle arrest and apoptosis. To that end, the field of apoptosis research has been moving forward at an alarmingly rapid rate. Although many of the key apoptotic proteins have been identified, the molecular mechanisms of action or inaction of these proteins remain to be elucidated. The goal of this review is to provide a general overview of current knowledge on the process of apoptosis including morphology, biochemistry, the role of apoptosis in health and disease, detection methods, as well as a discussion of potential alternative forms of apoptosis.