Brock Patrick M, Goodman Simon J, Hall Ailsa J, Cruz Marilyn, Acevedo-Whitehouse Karina
Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G61 1QH, UK.
Zoological Society of London, Regent's Park, London, NW1 4RY, UK.
BMC Evol Biol. 2015 Nov 4;15:242. doi: 10.1186/s12862-015-0519-6.
A multitude of correlations between heterozygosity and fitness proxies associated with disease have been reported from wild populations, but the genetic basis of these associations is unresolved. We used a longitudinal dataset on wild Galapagos sea lions (Zalophus wollebaeki) to develop a relatively new perspective on this problem, by testing for associations between heterozygosity and immune variation across age classes and between ecological contexts.
Homozygosity by locus was negatively correlated with serum immunoglobulin G production in pups (0-3 months of age), suggesting that reduced genetic diversity has a detrimental influence on the early development of immune defence in the Galapagos sea lion. In addition, homozygosity by locus was positively correlated with total circulating leukocyte concentration in juveniles (6-24 months of age), but only in a colony subject to the anthropogenic environmental impacts of development, pollution and introduced species, which suggests that reduced genetic diversity influences mature immune system activity in circumstances of high antigen exposure.
These findings demonstrate the environmental context-dependency of the phenotypic expression of immune variation, which is implicit in the theory of ecoimmunology, but which has been rarely demonstrated in the wild. They also indicate that heterozygosity may be linked to the maintenance of heterogeneity in mammalian immune system development and response to infection, adding to the body of evidence on the nature of the mechanistic link between heterozygosity and fitness.
野生种群中已报道了杂合性与多种疾病相关的健康指标之间存在众多关联，但这些关联的遗传基础仍未明确。我们利用加拉帕戈斯海狮（Zalophus wollebaeki）的纵向数据集，通过测试不同年龄组以及不同生态环境下杂合性与免疫变异之间的关联，对这一问题提出了一个相对新颖的观点。
按基因座计算的纯合性与幼崽（0 - 3个月龄）血清免疫球蛋白G的产生呈负相关，这表明遗传多样性降低对加拉帕戈斯海狮免疫防御的早期发育有不利影响。此外，按基因座计算的纯合性与幼年期（6 - 24个月龄）的总循环白细胞浓度呈正相关，但仅在受开发、污染和外来物种等人为环境影响的一个群体中如此，这表明在高抗原暴露情况下，遗传多样性降低会影响成熟免疫系统的活性。
这些发现证明了免疫变异表型表达对环境背景的依赖性，这在生态免疫学理论中是隐含的，但在野外很少得到证实。它们还表明，杂合性可能与哺乳动物免疫系统发育和对感染反应的异质性维持有关，这进一步补充了关于杂合性与健康之间机制联系本质的证据。
