The role of neutrophil granulocytes as target cells and transport vehicle for intracellular pathogens

中性粒细胞（PMN）被迅速招募到感染了利什曼原虫（L. major）的皮肤上，并且PMN最近被证明可以促进利什曼原虫病的发展。我们发现PMN在体内和体外都能吞噬利什曼原虫。重要的是，寄生虫延缓了感染PMN的自发凋亡至少24-72小时，因此，寄生虫在PMN的细胞内存活。这些数据表明，PMN的入侵是确定利什曼感染的重要早期步骤。本研究的目的是了解PMN在细胞内病原体感染后疾病发展中的作用。本研究将探讨PMN识别利什曼原虫的分子基础及病原性抑制PMN凋亡的机制。一旦利什曼原虫使用的抗凋亡途径被明确，将测试这是否是细胞内病原体抑制PMN凋亡的一般机制。在这些实验中，将使用肺炎衣原体，一种我们已经证明可以抑制PMN凋亡的细菌。实验计划分析PMN作为利什曼原虫和衣原体的运输载体在病原体“无声进入”单核/巨噬细胞中的作用。为了了解感染中PMN功能的分子机制，将进行cDNA微阵列分析，以鉴定中性粒细胞暴露于细胞内病原体后表达的基因。

Neutrophil granulocytes (PMN) are recruited rapidly to the skin infected with Leishmania major (L. major) and PMN have been recently shown to facilitate the development of leishmanial disease. We have found that PMN are able to phagocytose Leishmania promastigotes both in vitro and in vivo. Importantly, the parasites delay the spontaneous apoptosis of infected PMN for at least 24-72 h and, as a result, parasites survive intracellularly in PMN. These data suggested that the invasion of PMN is an important early step to establish the leishmanial infection. The aim of the proposed study is to understand the role of PMN in the disease development after infection with intracellular pathogens. The study will investigate the molecular basis of recognition of Leishmania by PMN and the mechanism of pathogeninduced inhibition of PMN apoptosis. Once the anti-apoptotic pathway used by Leishmania is clarified, it will tested whether this is a general mechanism of intracellular pathogens to inhibit PMN apoptosis. In these experiments Chlamydia pneumoniae will be used, a bacterium which we have shown to inhibit PMN apoptosis as well. Experiments are planned to analyse the role of PMN as transport vehicle of Leishmania and Chlamydia contributing to the "silent entry" of the pathogens into monocytes/ macrophages. In order to understand the molecular mechanisms of PMN function in an infection, cDNA microarray analysis will be carried out to identify genes expressed by neutrophils after exposure to intracellular pathogens.