Legionella pneumophila down-regulates MHC class I expression of human monocytic host cells and thereby inhibits T cell activation

Legionella (L.) pneumophila, the causative agent of Legionnaires disease, is an intracellular pathogen of alveolar macrophages that resides in a compartment displaying features of endoplasmatic reticulum (ER). In this study, we show that intracellular multiplication of L. pneumophila results in a remarkable decrease in MHC class I expression by the infected monocytes. During intracellular multiplication, L. pneumophila absorbs ER-resident chaperons such as calnexin and BiP, molecules that are required for the correct formation of the MHC class I complex. Due to reduced MHC class I expression, stimulation of allogeneic blood mononuclear cells was severely inhibited by infected host cells but cytotoxicity of autologous natural killer cells against Legionella-infected monocytes was not enhanced. Thus, reduced expression of MHC class I in infected monocytes may resemble a new immune escape mechanism induced by L. pneumophila.Received 22 November 2004; received after revision 27 December 2004; accepted 5 January 2005     

抗原处理相关转运体( TAP) 的结构和功能研究进展

摘要: 抗原处理相关转运体( TAP) 属于 ABC( ATP-binding cassette) 转运体超家族的 B 亚家族,是由主要组织相容性 复合体( Major histocompatibility complex ,MHC) 上 2 个紧密连锁的基因 TAP1 和 TAP2 编码蛋白组成的异二聚体,位 于内质网和顺式高尔基膜上,功能是将抗原肽从细胞质转运进入内质网池,组装到 MHC I 类分子上构成复合体。 TAP 蛋白的缺乏和突变会影响抗原肽的提呈,最终损害免疫应答功能。     

A Hand Gesture Based Interactive Presentation System Utilizing Heterogeneous Cameras

In this paper, a real-time system that utilizes hand gestures to interactively control the presentation is proposed. The system employs a thermal camera for robust human body segmentation to handle the complex background and varying illumination posed by the projector. A fast and robust hand localization algorithm is proposed, with which the head, torso, and arm are sequentially localized. Hand trajectories are segmented and recognized as gestures for interactions. A dual-step calibration algorithm is utilized to map the interaction regions between the thermal camera and the projected contents by integrating a Web camera. Experiments show that the system has a high recognition rate for hand gestures, and corresponding interactions can be performed correctly.     

科技论文的“致谢”问题不容忽视

总结分析了目前科技论文中对"致谢"的多种存在形式及其不规范表述问题,剖析了问题产生的根源,以实例给予纠正,并提出了对应克服问题的建议.     

通用目标检测算法研究进展与评述

通用目标检测是计算机视觉和模式识别领域中最活跃的研究主题之一,在图像检索、目标识别、辅助驾驶系统以及视觉监控等许多方面都有着重要应用.目标检测研究中要解决的基本问题是,如何选取目标特征,以及如何利用这些特征描述目标物体.一般情况下,目标物体的描述方法跟目标特征的选取原则密切相关.论文从两类典型的特征类型出发,对目标检测研究的暨有成果加以回顾与评述,并对可能的发展趋势进行分析.     

基于FFT与Mason公式的仿真研究

本文应用ＦＦＴ及梅森公式对线性系统仿真，首先介绍基于ＤＦＴ的频域仿真原理，然后借助梅森公式完成多输入多输出线性系统的仿真，文中给出仿真程序流程，并通过实例说明仿真的可行性和实用性。     

指纹图像准确采集和显现

阐述了指纹图像准确采集和显现的重要性，有针对性地引入了对现场不规范指纹采集的许多重要知识和经验，使公安的专业知识和经验与计算机知识得到了有机的统一。     

应急图标呈现方式及亮度对比对认知绩效的影响

应急图标的认知绩效在紧急救援中起重要作用。为探究应急图标呈现方式及亮度对比的变化对认知绩效的影响机理,采用视觉搜索范式并采用眼动实验进行结果验证。实验a结果表明,高、中载荷下,应急图标呈现方式和亮度对比的主效应明显,反色应急图标的搜索速度明显快于图形应急图标和带边框应急图标,亮度对比中0.90的搜索平均反应时间最短,0.10、0.30、0.60的平均反应时间有随亮度对比升高而降低的趋势;低载荷下,应急图标呈现方式和亮度对比对认知绩效的影响不明显。实验b眼动实验结果表明,高、中载荷下,反色应急图标注视时间明显低于其他呈现方式,亮度对比较高（0.90）的带边框应急图标平均注视时间明显低于低亮度对比,注视时间有随对比度增大而降低的趋势;低载荷下图标呈现方式、亮度对比注视时间无明显差异。高、中、低载荷下注视点的个数无明显差异,解释了实验a的结果。主观评价的评分也对实验结果做出了认知方面的解释。研究表明,应急图标呈现方式及亮度对比对认知绩效具有显著影响。     

Endothelial cells as antigen-presenting cells: role in human transplant rejection

The immunological properties of human endothelial cells suggest they perform a pivotal role in acute and chronic rejection following solid organ transplantation. In this review the basic features of acute and chronic rejection are described as are the cellular and molecular requirements for antigen presentation. Traditionally, antigen-presenting cells are considered to be bone marrow-derived cells. However, these conclusions have been derived from rodent models of allograft rejection where bone marrow-derived passenger leukocytes are the only source of donor major histocompatibility complex (MHC) class II in the grafted organ. In contrast, in humans, virtually all the microvascular and small vessel endothelial cells are ‘constitutively’ positive for MHC class II antigens. The phenotypic properties of human endothelial cells, their response to cytokines and their ability to stimulate resting T cells are described. Unlike bone marrow-derived antigen presenting cells (APCs), which utilise B7/CD28 interactions, human endothelial cells utilise lymphocyte function antigen 3 (LFA3)/CD2 pathways to stimulate T cells. They activate a CD45RO + B7-independent subpopulation of T cells. Their effect on allogeneic T cells is compared with other non-bone marrow-derived cells such as fibroblasts, epithelial cells and smooth muscle cells, which are unable to stimulate resting T cells. Evidence is presented suggesting that release of MHC and non-human leukocyte antigens (HLA) from endothelial cells stimulates an alloantibody and autoimmune response leading to chronic rejection. Received 30 March 1998; received after revision 4 May 1998; accepted 4 May 1998     

化工过程安全评价中危险剧情的表达与识别

在现有各类安全评价方法的基础上,从信息展示及知识表示两方面着重对危险剧情的表达进行了阐述,提出一种图形化的基于知识本体的危险剧情表达方法,并在开发的软件平台实现了危险剧情的计算机自动识别与分析。工业实例应用结果表明,这种方法不但提高了分析的质量与效率,而且由于其标准化的信息表达方法,使得安全信息传递、审核与共享更加容易。