Department of Integrative Biology, University of South Florida, , SCA 110, Tampa, FL 33620, USA, Department of Biology, Armstrong Atlantic State University, , Savannah, GA 31419, USA.
Proc Biol Sci. 2013 Nov 20;281(1774):20132690. doi: 10.1098/rspb.2013.2690. Print 2014 Jan 7.
Interactions between hosts and parasites influence the success of host introductions and range expansions post-introduction. However, the physiological mechanisms mediating these outcomes are little known. In some vertebrates, variation in the regulation of inflammation has been implicated, perhaps because inflammation imparts excessive costs, including high resource demands and collateral damage upon encounter with novel parasites. Here, we tested the hypothesis that variation in the regulation of inflammation contributed to the spread of house sparrows (Passer domesticus) across Kenya, one of the world's most recent invasions of this species. Specifically, we asked whether inflammatory gene expression declines with population age (i.e. distance from Mombasa (dfM), the site of introduction around 1950). We compared expression of two microbe surveillance molecules (Toll-like receptors, TLRs-2 and 4) and a proinflammatory cytokine (interleukin-6, IL-6) before and after an injection of an immunogenic component of Gram-negative bacteria (lipopolysaccharide, LPS) among six sparrow populations. We then used a best-subset model selection approach to determine whether population age (dfM) or other factors (e.g. malaria or coccidian infection, sparrow density or genetic group membership) best-explained gene expression. For baseline expression of TLR-2 and TLR-4, population age tended to be the best predictor with expression decreasing with population age, although other factors were also important. Induced expression of TLRs was affected by LPS treatment alone. For induced IL-6, only LPS treatment reliably predicted expression; baseline expression was not explained by any factor. These data suggest that changes in microbe surveillance, more so than downstream control of inflammation via cytokines, might have been important to the house sparrow invasion of Kenya.
宿主和寄生虫之间的相互作用会影响引入后宿主的成功和范围的扩展。然而，介导这些结果的生理机制知之甚少。在一些脊椎动物中，炎症调节的变化可能与此有关，因为炎症会带来过度的代价，包括与新寄生虫相遇时的高资源需求和附带损害。在这里，我们检验了这样一个假设，即炎症调节的变化可能是导致家麻雀（Passer domesticus）在肯尼亚扩散的原因之一，这是该物种最近的一次入侵之一。具体来说，我们询问了炎症基因表达是否随种群年龄（即距离蒙巴萨（Mombasa）的距离，1950 年左右的引入地点）而下降。我们比较了 6 个麻雀种群在注射革兰氏阴性菌（脂多糖，LPS）的免疫原性成分前后两种微生物监测分子（Toll 样受体，TLR-2 和 TLR-4）和一种促炎细胞因子（白细胞介素-6，IL-6）的表达。然后，我们使用最佳子集模型选择方法来确定种群年龄（dfM）或其他因素（例如疟疾或球虫感染、麻雀密度或遗传群体成员）是否能最好地解释基因表达。对于 TLR-2 和 TLR-4 的基线表达，种群年龄往往是最好的预测因子，表达随着种群年龄的增加而下降，尽管其他因素也很重要。TLRs 的诱导表达受 LPS 处理的单独影响。对于诱导的 IL-6，只有 LPS 处理才能可靠地预测表达；任何因素都不能解释基线表达。这些数据表明，微生物监测的变化，而不是通过细胞因子对炎症的下游控制，可能对家麻雀入侵肯尼亚很重要。
