Regulation of host defense reaction gy parasitoid

寄生蜂的卵和幼虫在合适的寄主上发生寄生时，均可避免寄主的防御反应。在本项目中，分析了卵和幼虫没有被包被在寄主的血腔中的原因，这是在假线虫-Cotesiakariyai系统中。将葡聚糖珠作为异物注入寄主体内，观察寄生对微囊化能力的影响。葡聚糖珠周围的包膜层厚度随产卵后天数的增加而减小。其厚度的减少似乎取决于两个原因：血细胞数量的减少或受体血细胞的改变来区分异物。然而，血细胞数量的完全抑制使寄生蜂处于不利地位，因为它容易被细菌感染。血细胞总数计数表明，寄生后1天内血细胞数较未寄生寄主减少1/5，并一直维持到出现寄生蜂。在被寄生的寄主中，短期内血细胞数量的减少是由多聚核糖核酸病毒和毒液共同引起的，这些毒液在产卵时注射到寄主体内。人工注射多聚核糖核酸病毒和蛇毒均可在注射后1小时内引起血细胞数量减少。玻片上附着的血细胞与抗异物胶囊化过程密切相关。随着产卵天数的增加，附着血细胞的数量也逐渐减少。随着寄生期的延长，经Parcoll梯度分离的血细胞组分中粒细胞明显减少。在体外孵育系统中，蛇毒包被的Sephadex小球在注射前6h很难被多聚核糖核酸病毒和蛇毒预处理的血细胞包裹。这些结果表明，在卵期，涂有毒液的鸡蛋很难区分为异物。此外，同时，由于多聚核糖核酸病毒和多聚核糖核酸病毒的作用，血细胞数量减少

Both eggs and larvae of parasitoids can avoid defense reaction of hosts when parasitization occurred in suitable host. In this project, the reason why eggs and larvae are not encapsulated in the hemocoel of host was anslysed in Pseudaletia-Cotesiakariyai system. To examine the change of the ability of encapsulation by parasitization, Sephadex beads as foreign substance were injected into hosts. Thickness of encapsulation layr around Sephadex beads decreased with lapse of days after oviposition. Its decreasing thickness seems to depend on two causes : decreasing of number of hemocytes or change of receptor hemocytes to discriminate the foreigh substances. However, completely depression of number of hemocytes made the parasitoid disadvantage because of easy infection by bacteria. Counting of total hemocyte made clear that number of hemocytes decreased to 1/5 compared with one of unparasitized hosts in one days after parasitization, was maintained until emerge of parasitoid. Decreasing the number of hemocytes for a short term in parasitized host was caused by both polydnavirus and venom, which was injected into the host at the time of oviposition. Artificial injection of both polydnavirus and venom caused reduced number of hemocytes within 1 hr post-injection. Attached hemocytes on glass plate were so related with processing of encapsulation against foreign materials. Number of attached hemocytes was also decreased with lapse of days after oviposition. A fewer granulocyte in hemocyte fraction separated by parcoll gradient was observed with lapse of days after parasitization. Sephadex beads coated with venom were hard to be encapsulated by hemocytes preconditioned with polydnavirus and venom 6 h before injection in in vitro incubation system. These results suggested that during egg stage, eggs coated with venom was hard to be distinguished as foreign substance. Additionally, at the same time, the number of hemocytes was decreased by the function of both polydnavirus an