State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
PLoS One. 2012;7(5):e37182. doi: 10.1371/journal.pone.0037182. Epub 2012 May 23.
Life history theory assumes there are trade-offs between competing functions such as reproduction and immunity. Although well studied in birds, studies of the trade-offs between reproduction and immunity in small mammals are scarce. Here we examined whether reduced immunity is a consequence of reproductive effort in lactating Brandt's voles (Lasiopodomys brandtii). Specifically, we tested the effects of lactation on immune function (Experiment I). The results showed that food intake and resting metabolic rate (RMR) were higher in lactating voles (6≤ litter size ≤8) than that in non-reproductive voles. Contrary to our expectation, lactating voles also had higher levels of serum total Immunoglobulin G (IgG) and anti-keyhole limpet hemocyanin (KLH) IgG and no change in phytohemagglutinin (PHA) response and anti-KLH Immunoglobulin M (IgM) compared with non-reproductive voles, suggesting improved rather than reduced immune function. To further test the effect of differences in reproductive investment on immunity, we compared the responses between natural large (n≥8) and small litter size (n≤6) (Experiment II) and manipulated large (11-13) and small litter size (2-3) (Experiment III). During peak lactation, acquired immunity (PHA response, anti-KLH IgG and anti-KLH IgM) was not significantly different between voles raising large or small litters in both experiments, despite the measured difference in reproductive investment (greater litter size, litter mass, RMR and food intake in the voles raising larger litters). Total IgG was higher in voles with natural large litter size than those with natural small litter size, but decreased in the enlarged litter size group compared with control and reduced group. Our results showed that immune function is not suppressed to compensate the high energy demands during lactation in Brandt's voles and contrasting the situation in birds, is unlikely to be an important aspect mediating the trade-off between reproduction and survival.
生活史理论假设在繁殖和免疫等竞争功能之间存在权衡。尽管在鸟类中得到了很好的研究，但对小型哺乳动物中繁殖和免疫之间的权衡研究却很少。在这里，我们研究了哺乳期 Brandt 田鼠（Lasiopodomys brandtii）的繁殖努力是否会降低免疫力。具体来说，我们测试了哺乳期对免疫功能的影响（实验 I）。结果表明，哺乳期（6≤窝仔数≤8）田鼠的食物摄入量和静息代谢率（RMR）高于非繁殖田鼠。与我们的预期相反，与非繁殖田鼠相比，哺乳期田鼠的血清总免疫球蛋白 G（IgG）和抗血蓝蛋白 IgG 水平也更高，植物血球凝集素（PHA）反应和抗血蓝蛋白 IgM 没有变化，表明免疫功能得到改善而不是降低。为了进一步测试繁殖投资差异对免疫的影响，我们比较了自然大（n≥8）和小窝仔数（n≤6）（实验 II）以及大（11-13）和小窝仔数（2-3）（实验 III）之间的反应。在哺乳期高峰期，尽管在繁殖投资方面存在差异（产仔较多的田鼠具有较大的窝仔数、窝仔质量、RMR 和食物摄入量），但在两个实验中，产仔较大或较小窝仔的田鼠的获得性免疫（PHA 反应、抗血蓝蛋白 IgG 和抗血蓝蛋白 IgM）没有明显差异。与自然小窝仔数的田鼠相比，自然大窝仔数的田鼠总 IgG 更高，但与对照组和减少组相比，大窝仔数组的 IgG 降低。我们的结果表明，免疫功能没有受到抑制，以补偿 Brandt 田鼠哺乳期的高能量需求，与鸟类的情况相反，它不太可能是繁殖和生存之间权衡的重要方面。
