在受到寄生蟲(chóng)、病毒等病原體的攻擊時(shí),，動(dòng)物最常見(jiàn)的做法是通過(guò)免疫系統(tǒng)進(jìn)行抵抗,。不過(guò)，英國(guó)科學(xué)家對(duì)小鼠的一項(xiàng)最新研究表明，宿主抵御入侵還有另外一種選擇,，那就是妥協(xié),，逐漸進(jìn)化為與入侵者共同生存。這一發(fā)現(xiàn)有望加深科學(xué)家對(duì)進(jìn)化和傳染病擴(kuò)散的理解,，并創(chuàng)造出更優(yōu)良的家畜品種,。相關(guān)論文發(fā)表在11月2日的《科學(xué)》雜志上。
植物有兩種對(duì)付病原的策略：發(fā)展出強(qiáng)大的防御機(jī)制來(lái)進(jìn)行抵抗,，或者忍耐并盡量減少入侵者造成的傷害,，比如它們會(huì)增加自身的光合作用，促進(jìn)能量存儲(chǔ),。很少有植物能夠同時(shí)利用這兩種方式,。
為了弄清動(dòng)物是否也會(huì)做出類似的選擇，英國(guó)愛(ài)丁堡大學(xué)的生態(tài)學(xué)家Lars Råberg和同事讓5種小鼠感染上能導(dǎo)致瘧疾的寄生蟲(chóng),。隨后,，研究人員對(duì)這些小鼠的健康狀況進(jìn)行了監(jiān)控，并測(cè)量了它們貧血和體重減輕的情況,，這與血管中寄生蟲(chóng)的總量相關(guān),。
研究人員發(fā)現(xiàn)，與植物類似,，這些小鼠也會(huì)采取強(qiáng)硬或者妥協(xié)兩種方式,。隨著宿主體內(nèi)寄生蟲(chóng)數(shù)量的加倍，一些小鼠種系會(huì)比另一些更加健康,，這表明它們發(fā)展出了忍耐病原體的方法。此外,，還有一些種系的小鼠能夠保持寄生蟲(chóng)數(shù)量處于較低的水平,，這說(shuō)明它們能夠主動(dòng)地抵御感染。
不過(guò),，研究人員注意到,，一種小鼠不會(huì)同時(shí)采取抵御策略與妥協(xié)策略，也就是無(wú)法“軟硬兼施”,。那些能夠更頑強(qiáng)進(jìn)行抵御的小鼠,，對(duì)寄生蟲(chóng)的忍耐力卻更差。與忍耐性強(qiáng)的小鼠相比,，它們的體重會(huì)減輕更多,，而且變得更加貧血。Råberg表示,，這一現(xiàn)象或許說(shuō)明,，小鼠主導(dǎo)妥協(xié)策略和抵抗策略的深層遺傳學(xué)機(jī)制是不同的。此外,，新的發(fā)現(xiàn)還揭示出病原體進(jìn)化的重要特征,，即如果宿主選擇妥協(xié),，它們就不會(huì)急于發(fā)展出更強(qiáng)的致命性。同時(shí),，妥協(xié)并不是一種十分理想的策略,，因?yàn)槿绻麢C(jī)體不破壞殺滅這些病原體，它們就更有可能發(fā)生傳播和擴(kuò)散,。
美國(guó)杜克大學(xué)的進(jìn)化生物學(xué)家Mark Rausher表示,，新的發(fā)現(xiàn)有望影響家畜培育策略，讓雞和豬具有更大的忍耐性或許能更好地抵御病原攻擊,。（科學(xué)網(wǎng) 任霄鵬/編譯）
原始出處:
Science 2 November 2007:
Vol. 318. no. 5851, pp. 812 - 814
DOI: 10.1126/science.1148526
Disentangling Genetic Variation for Resistance and Tolerance to Infectious Diseases in Animals
Lars Råberg,1,2* Derek Sim,1 Andrew F. Read1
Hosts can in principle employ two different strategies to defend themselves against parasites: resistance and tolerance. Animals typically exhibit considerable genetic variation for resistance (the ability to limit parasite burden). However, little is known about whether animals can evolve tolerance (the ability to limit the damage caused by a given parasite burden). Using rodent malaria in laboratory mice as a model system and the statistical framework developed by plant-pathogen biologists, we demonstrated genetic variation for tolerance, as measured by the extent to which anemia and weight loss increased with increasing parasite burden. Moreover, resistance and tolerance were negatively genetically correlated. These results mean that animals, like plants, can evolve two conceptually different types of defense, a finding that has important implications for the understanding of the epidemiology and evolution of infectious diseases.
1 Institute of Evolutionary Biology and Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK.
2 Department of Animal Ecology, Lund University, Ecology Building, 223 62 Lund, Sweden.
Present address: Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, 208 Mueller Lab, University Park, PA 16802, USA.
* To whom correspondence should be addressed. E-mail: [email protected]
