Abstract：
Among terrestrial ectotherms, hibernation is a common response to extreme cold temperatures and is associated with reduced physiological rates, including immunity. When winter wanes and temperatures increase, so too do vital rates of both ectothermic hosts and their parasites. Due to metabolic scaling, if parasite activity springs back faster than host immune functions then cold seasons and transitions between cold and warm seasons may represent periods of vulnerability for ectothermic hosts. Understanding host regulation of physiological rates at seasonal junctions is a first step toward identifying thermal mismatches between hosts and parasites. Here we show that immune gene expression is responsive to transitions into and out of the cold season in a winter-adapted amphibian, the wood frog (Lithobates sylvaticus), and that frogs experienced parasitism by at least two nematode species throughout the entirety of the cold season. In both splenic and skin tissues, we observed a decrease in immune gene expression going from fall to winter, observed no changes between winter and emergence from hibernation, and observed increases in immune gene expression after hibernation ended. At all timepoints, differentially expressed genes from spleens were more highly enriched for immune system processes than those from ventral skin, especially with respect to terms related to adaptive immune processes. Infection with nematode lungworms was also associated with upregulation of immune processes in the spleen. We suggest that rather than being a period of stagnation, during which physiological processes and infection potential cease, the cold season is immunologically dynamic, requiring coordinated regulation of many biological processes, and that the reemergence period may be an important time during which hosts invest in preparatory immunity.
摘要：
在陆地外温带中，冬眠是对极端寒冷温度的常见反应，并且与降低的生理速率有关，包括豁免权。当冬季减弱和气温升高时，放热宿主及其寄生虫的生命速率也是如此。由于代谢结垢，如果寄生虫活动的恢复速度比宿主的免疫功能快，那么寒冷季节以及寒冷和温暖季节之间的过渡可能代表了放热宿主的脆弱时期。了解季节性交界处的生理速率的宿主调节是识别宿主和寄生虫之间的热错配的第一步。在这里，我们表明免疫基因表达对冬季适应的两栖动物进入和离开寒冷季节的转变有反应，木蛙（Lithobotessylvaticus），在整个寒冷季节，青蛙经历了至少两种线虫的寄生。在脾和皮肤组织中，我们观察到从秋季到冬季免疫基因表达下降，观察到冬季和冬眠之间没有变化，并观察到冬眠结束后免疫基因表达的增加。在所有时间点，与腹侧皮肤相比，脾脏的差异表达基因对免疫系统过程的富集程度更高，特别是与适应性免疫过程相关的术语。线虫肺虫的感染也与脾脏中免疫过程的上调有关。我们建议，与其是停滞期，在此期间，生理过程和潜在的感染停止，寒冷的季节是免疫动态的，需要协调调节许多生物过程，并且重新出现的时期可能是主机投资准备免疫的重要时期。
