Immunotoxicological Studies on thymocyte apoptosis and immunotoxicity which the organophosphorus insecticide induces

毒死蜱(CP)和敌敌畏(ECP)是广泛使用的有机磷杀虫剂。为探讨环磷酰胺和环磷酰胺对免疫毒性靶器官大鼠胸腺的免疫毒性作用，对F344大鼠胸腺进行了体内外研究。为评价胸腺细胞同时暴露于CP和ECP的体外效应，采集大鼠胸腺细胞培养物，进行DNA含量的流式细胞仪分析。为研究CP和ECP的体内效应，将雄性F344大鼠分别灌胃染毒CP(10，20，40 mg/kg)和ECP(20，40，80 mg/kg)，连续7天。通过流式细胞仪分析，发现CP和ECP对大鼠胸腺细胞具有剂量依赖性的诱导凋亡作用，其DNA含量低于二倍体。关于CP和ECP的体内效应，我们发现CP和ECP在最高剂量下都能引起明显的胸腺萎缩。胸腺细胞亚群检测显示，CD4、CD8细胞作为未成熟细胞的百分比显著降低。采用组织化学方法，对胸腺进行ECP处理。皮质区CD4、CD8细胞较空白对照组少。ECP处理组大鼠大脑皮质内含有细胞碎片的巨噬细胞数量增多。这些巨噬细胞可能与随后的吞噬作用清除死亡细胞残留物有关。这些结果表明，CP和ECP导致胸腺萎缩和CD_4、CD_8未成熟细胞比例降低，这可能与细胞凋亡有关。

Chlorpyrifos (CP) and dichlofenthion (ECP) are widely used as organophosphorus insecticide. The purpose of this study is to examine the immunotoxicological effects of CP and ECP on the thymus of rat as target organ of immunotoxicty.The thymus of the F344 rat was studied in vitro and in vivo. For studies assessing the in vitro effect of si multaneous exposure of thymocytes to CP and ECP, rat thymocytes cultures were harvested and processed for flow cytometric analysis of DNA content. For the in vivo effect of CP and ECP, male F344 rats were exposed to CP (10, 20, 40mg/kg) and ECP (20, 40, 80mg/kg) by gavage, daily for 7 days.We observed that rat thymocytes cultures exposed to CP and ECP exhibited dose-dependent induction of apoptosis as a discrete subpopulation containing less than the diploid complement of DNA when analyzed by flow cytometry. On the in vivo effect of CP and ECP, we found that CP and ECP treatment induced significant thymic atrophy on highest dose. Determination of the thymocytes subpopulation showed a significant reduction of percentage of CD4+CD8+ cells as immature cells. Using a histochemical approach, on the thymus of ECP treatment. CD4+CD8+ cell in cortex were less frequently observed than vehicle control. The cortex of ECP-treated rat showed increased numbers of macrophages containing cell debris. These macrophages may correlate with subsequent removal of dead cell remnants by phagocytosis.These results suggest that CP and ECP induced thymus atrophy and reduction of percentage of CD4+CD8+ cells as immature cells, which might associate with apoptosis.