Interaction of microvesicles and bacterial toxins with immune cells

描述(由申请人提供)：避免免疫反应是许多病原体生物学的一个重要方面，已经定义了各种各样的机制。对于革兰氏阳性细菌，分泌属于胆固醇依赖细胞溶血素(CDC)家族的蛋白质在高浓度时可能导致某些细胞类型的溶解，但在较低浓度时也可能通过参与TLR4的参与而使巨噬细胞等细胞对凋亡诱导刺激敏感。最近报道了炭疽杆菌产生的CDC然而，刺激TLR可以被认为是一把双刃剑，因为这也可能刺激免疫反应，特别是当涉及到强大的ARC时，如树突状细胞(DC)。我们研究了三种CDC蛋白，即花青素O、破伤风毒素O和链球菌溶血素O的作用，观察到人DC对无毒水平的这些蛋白的处理迅速反应，其方式是熔融钙，然后分泌或脱落表面含有II类MHC蛋白的微泡(MV)。与此同时，DC失去了上调第二类MHC以响应IPS的能力。根据这些结果，我们推测CDC通过诱导含有第II类MHC的MV和其他在病原体相遇时对抗原提呈功能至关重要的蛋白质的分泌来损害DC的抗原提呈。此外，我们认为释放的MV本身可能具有免疫抑制特性，基于与称为外体的囊泡的相似性，CDC毒素可能在全身传播并被吞噬细胞摄取，这种方式对抗原提呈的影响比感染部位更广泛。我们建议进一步研究具有代表性的CDC蛋白TLO对人单核细胞来源的DC功能的影响，并从以下几个方面研究TLO诱导的MV对免疫反应的影响：1.TLO如何影响MoDC中II类分子的定位；2.TLO诱导的MV的蛋白质含量；3.细胞产生和摄取MV的机制；4.TLO诱导和结构性产生的MV对CD4和CDS T细胞功能的影响。莱伊声明；了解细菌毒素是如何影响免疫反应的，有助于设计出治疗破伤风、链球菌疾病和炭疽的新疗法。

Description (provided by applicant): Avoidance of the immune response is an important aspect of the biology of many pathogens, and a wide variety of mechanisms have been defined. For Gram-positive bacteria, secretion of proteins belonging to the family of cholesterol dependent cytolysins (CDC) may lead to lysis of some cell types at high concentrations, but at lower concentrations may also sensitize cells such as macrophages to apoptosis-inducing stimuli by engagement of TLR4. This was recently reported for anthrolysin O, a CDC produced by B. anthracis, and for a number of other CDC family members. Stimulation of TLR however could be considered a double edged sword, since this might also stimulate the immune response, particularly when involving potent ARC such as dendritic cells (DC). We have investigated the effects of three CDC proteins, anthrolysin O, tetanolysin O and streptolysin O, and observed that human DC rapidly respond to treatment with non-toxic levels of these proteins by fluxing calcium and then secreting or shedding microvesicles (MV) that have on their surface class II MHC proteins. At the same time, DC lose the ability to up-regulate class II MHC in response to IPS. Based on these results, we hypothesize that CDC act to impair antigen presentation by DC by inducing secretion of MV containing class II MHC and other proteins important to antigen presenting function precisely at the time of pathogen encounter. Furthermore, we suggest that released MV may themselves have immunosuppressive properties, based on similarities to vesicles called exosomes, and that CDC toxins might be disseminated throughout the body and taken up by phagocytes, in this way impacting antigen presentation more widely than at the site of infection. We propose to further characterize these effects of a representative CDC protein, TLO, on the function of human monocyte-derived DC and to investigate the impact of TLO-induced MV on immune reponses in the following aims: 1. how TLO affects class II localization in moDC will be determined; 2. the protein contents of TLO-induced MV will be characterized; 3. the mechanism of MV production and uptake by cells will be probed; 4. the effect of TLO-induced and constitutively produced MV on CD4 and CDS T cell function will be determined. Lay statement; Understanding how toxins from bacteria affect the immune response could help devise new treatments for tetanus, streptococcal disease, and anthrax.