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.

Peptide and protein antigens require distinct antigen-presenting cell subsets for the priming of CD4+ T cells.

Abstract: Priming of naive CD4+ T cells to Ag requires an antigen-presenting cell (APC) that can take up the Ag and present peptide bound to MHC class II molecules. We have used both in vivo and in vitro approaches to demonstrate that the APC used to prime naive CD4+ T cells depends on the initial form in which an Ag is administered. Although Ag delivered as a peptide was presented most efficiently to CD4+ T cells by DC, these APC were poor at priming to a protein form of the same Ag. In contrast, the presence of B cells was a requisite for priming to protein Ag.

Inducible costimulator is essential for collagen-induced arthritis

Abstract: CD4+ helper Th cells play a major role in the pathogenesis of rheumatoid arthritis. Th cell activation, differentiation, and immune function are regulated by costimulatory molecules. Inducible costimulator (ICOS) is a novel costimulatory receptor expressed on activated T cells. We, as well as others, recently demonstrated its importance in Th2 cytokine expression and Ab class switching by B cells. In this study, we examined the role of ICOS in rheumatoid arthritis using a collagen-induced arthritis model. We found that ICOS knockout mice on the DBA/1 background were completely resistant to collagen-induced arthritis and exhibited absence of joint tissue inflammation. These mice, when immunized with collagen, exhibited reduced anti-collagen IgM Ab’s in the initial stage and IgG2a Ab’s at the effector phase of collagen-induced arthritis. Furthermore, ICOS regulates the in vitro and in vivo expression of IL-17, a proinflammatory cytokine implicated in rheumatoid arthritis. These data indicate that ICOS is essential for collagen-induced arthritis and may suggest novel means for treating patients with rheumatoid arthritis.

The Immunoglobulin (IgG) Antibody Response to OspA and OspB Correlates with Severe and Prolonged Lyme Arthritis and the IgG Response to P35 Correlates with Mild and Brief Arthritis

Abstract: In an effort to implicate immune responses to specific Borrelia burgdorferi proteins that may have a role in chronic Lyme arthritis, we studied the natural history of the antibody response to B. burgdorferi in serial serum samples from 25 patients monitored throughout the course of Lyme disease. In these patients, the immunoglobulin G (IgM) and IgG antibody responses to 10 recombinant B. burgdorferi proteins, determined during early infection, early arthritis, and maximal arthritis, were correlated with the severity and duration of maximal arthritis. The earliest responses were usually to outer surface protein C (OspC), P35, P37, and P41; reactivity with OspE, OspF, P39, and P93 often developed weeks later; and months to years later, 64% of patients had responses to OspA and OspB. During early infection and early arthritis, the levels of IgG antibody to P35 correlated inversely with the subsequent severity or duration of maximal arthritis. In contrast, during periods of maximal arthritis, the levels of IgG antibody to OspA and OspB, especially to a C-terminal epitope of OspA, correlated directly with the severity and duration of arthritis. Thus, the higher the IgG antibody response to P35 earlier in the infection, the milder and briefer the subsequent arthritis, whereas during maximal arthritis, the higher the IgG response to OspA and OspB, the more severe and prolonged the arthritis.

Reciprocal regulation of CD30 expression on CD4+ T cells by IL-4 and IFN-gamma.

Abstract: Prior studies have implicated CD30 as a marker for Th2 cells, but the mechanism that underlies this correlation was unknown We show here that CD30 was expressed on activated CD4+ T cells in the presence of IL-4 In the absence of endogenously produced IL-4, however, even Th2 lineage cells lost CD30 expression Thus, CD30 is not an intrinsic marker of Th2 cells, but is inducible by IL-4 CD30 was also found to be down-regulated by IFN-gamma Committed Th1 effector cells do not express CD30, although differentiating Th1 lineage cells temporarily express CD30 The transient expression of CD30 on differentiating Th1 lineage cells was mainly the result of endogenously produced IL-4 induced by IL-12 Culture of IL-12-primed cells under conditions that reverse the phenotype (Ag plus IL-4) resulted in two cell populations based upon their ability to express CD30 One population responded to IL-4 upon restimulation and became a CD30-positive, Th0-like cell population, while the other remained CD30 negative and synthesized only IFN-gamma Thus, CD30 expressed on CD4+ T cells reflected the ability of CD4+ T cells to respond to IL-4

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.