Insect parasitic nematodes have developed a mechanism to escape from the cellular immunity of their insect hosts for successful parasitism. However, the detailed mechanism whereby they achieve this remains unclear. In our previous study, we demonstrated that non-parasitic nematodes such as Caenorhabditis elegans potentially have the ability to escape from the cellular immunity of the greater wax moth Galleria mellonella. Here we aimed to clarify the effect of non-parasitic and parasitic nematodes on the spreading of hemocytes—an essential cellular reaction for adhering to a foreign substance —from G. mellonella larvae. The hexane/methanol extract of C. elegans inhibited the spreading of hemocytes. Using 2D-TLC and reversed-phase HPLC, we detected a single peak that inhibited the spreading of hemocytes. In addition, the spreading of hemocytes recovered from C. elegans-injected insects was significantly delayed. Western blotting analysis showed that phosphorylated extracellular signal-regulated protein kinase (ERK) —an essential signaling component for spreading in hemocytes—was decreased by the injection of C. elegans, and that plasma from nematode-injected insects contained the factor that causes the decrease of phosphorylated ERK. We also observed this phenomenon using other non-parasitic and parasitic bacterial-feeding nematodes. These results suggest that the factors inhibiting hemocyte adhesion and delaying the spreading of hemocytes are conserved in bacterial-feeding nematodes and could be a pre-adaptation for parasitism.

昆虫寄生线虫已经开发出一种机制，可以逃避其昆虫宿主的细胞免疫，从而成功实现寄生。但是，他们实现这一目标的详细机制仍不清楚。在我们之前的研究中，我们证明了非寄生性线虫（例如秀丽隐杆线虫）可能具有逃脱更大蜡蛾圆盘菌的细胞免疫的能力。在这里，我们旨在阐明非寄生线虫和寄生线虫对血吸虫幼虫血细胞扩散（一种粘附异物的重要细胞反应）的影响。秀丽隐杆线虫的己烷/甲醇提取物抑制血细胞的扩散。使用2D-TLC和反相HPLC，我们检测到一个抑制血细胞扩散的单峰。另外，从注射秀丽隐杆线虫的昆虫中回收的血细胞的扩散被显着延迟。蛋白质印迹分析表明，注射线虫后，磷酸化的细胞外信号调节蛋白激酶（ERK）（一种在血细胞中传播的重要信号成分）被降低了。，而线虫注射昆虫的血浆中含有导致磷酸化ERK降低的因子。我们还使用其他非寄生和寄生细菌摄食线虫观察到了这种现象。这些结果表明，在细菌饲养的线虫中，抑制血细胞粘附和延迟血细胞扩散的因素是保守的，并且可能是对寄生虫的预适应。