Elevated reproductive effort increases blood parasitaemia and decreases immune function in birds: a meta-regression approach
Elevated reproductive effort increases blood parasitaemia and decreases immune function in birds: a meta-regression approach
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DOI：
10.1111/j.1365-2435.2008.01507.x
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发表时间：
2009-04-01
影响因子：
5.2
通讯作者：
Sheldon, Ben C.
中科院分区：
文献类型：
--
作者：
Knowles, Sarah C. L.;Nakagawa, Shinichi;Sheldon, Ben C.
1.近年来，人们对涉及宿主免疫功能和寄生虫防御的生理权衡产生了浓厚的兴趣，有人认为它们可能在介导有据可查的生活史权衡中发挥关键作用，例如繁殖成本。在对鸟类的研究中，生殖努力和寄生虫防御之间的假设联系受到了特别的关注，但对这两种特征之间权衡的支持仍然模棱两可。我们使用元回归分析和信息论方法来调查，在鸟类研究中，实验性改变的生殖努力对（i）四种常见属（血变形菌属，白细胞虫属，锥虫属和疟原虫属）的血液寄生虫感染以及（ii）宿主对新抗原挑战产生免疫应答的能力的影响有多强。在所有研究中，生殖努力对血液寄生虫感染水平有相对较弱但得到充分支持的积极影响。重要的是，这种效应受到所采用的寄生虫学测量的显著影响;当寄生虫血症（受感染宿主内被寄生细胞的比例）被用作响应变量时，效应大小几乎是测量感染流行率（宿主之间存在或不存在感染）时的三倍。在多项研究中，还发现生殖努力对免疫反应性有中度负面影响。这种影响是更大的时间之间已经过去了较长的时间操作的生殖努力和测量的免疫反应，也与生殖努力被操纵的阶段，与操作期间育雏饲养产生更强的影响比操作期间孵化。总的来说，这些结果提供了证据表明，生殖努力可以对寄生和免疫反应产生明显的影响，但影响大小受方法的影响-测量什么和什么时候。这些影响究竟是如何产生的，以及它们是否足以为再生产成本提供一个机械解释，仍有待充分探讨。
1. In recent years there has been much interest in physiological trade-offs involving host immune function and parasite defence, with the suggestion that they could play a pivotal role in mediating well-documented life-history trade-offs, such as the cost of reproduction.2. Among studies of birds, the hypothesized link between reproductive effort and parasite defence has received particular attention, yet support for a trade-off between these two traits remains equivocal.3. We used meta-regression analysis and an information-theoretic approach to investigate, among avian studies, how strong the effect of experimentally altered reproductive effort is on (i) infection with blood parasites from four common genera (Haemoproteus, Leucocytozoon, Trypanosoma and Plasmodium) and (ii) the ability of hosts to mount an immune response to novel antigenic challenge.4. Across studies, there was a relatively weak but well-supported positive effect of reproductive effort on blood parasite infection levels. Importantly, this effect was significantly influenced by the parasitological measure employed; where parasitaemia (proportion of parasitized cells within infected hosts) was used as the response variable, effect size was almost three times as large as where infection prevalence (presence vs. absence of infection among hosts) was measured.5. A moderate negative effect of reproductive effort on immune responsiveness was also found across studies. This effect was greater the longer the time that had elapsed between manipulation of reproductive effort and measurement of immune responsiveness, and was also related to the stage at which reproductive effort was manipulated, with manipulation during brood rearing producing stronger effects than manipulation during incubation.6. Overall, these results provide evidence that reproductive effort can have pronounced effects on both parasitism and immune responses, but that effect size is influenced by methodology - what is measured and when. Exactly how such effects arise and whether they are sufficient to provide a mechanistic explanation for the cost of reproduction remains to be fully explored.