Data from: Multivariate immune defences and fitness in the wild: complex but ecologically important associations among plasma antibodies, health and survival

Despite our rapidly advancing mechanistic understanding of vertebrate immunity under controlled laboratory conditions, the links between immunity, infection and fitness under natural conditions remain poorly understood. Antibodies are central to acquired immune responses, and antibody levels circulating in vivo reflect a composite of constitutive and induced functional variants of diverse specificities (e.g. binding antigens from prevalent parasites, self tissues or novel non-self sources). Here, we measured plasma concentrations of 11 different antibody types in adult females from an unmanaged population of Soay sheep on St Kilda. Correlations among antibody measures were generally positive but weak, and eight of the measures independently predicted body mass, strongyle parasite egg count or survival over the subsequent winter. These independent and, in some cases, antagonistic relationships point to important multivariate immunological heterogeneities affecting organismal health and fitness in natural systems. Notably, we identified a strong positive association between anti-nematode immunoglobulin (Ig) G antibodies in summer and subsequent over-winter survival, providing rare evidence for a fitness benefit of helminth-specific immunity under natural conditions. Our results highlight both the evolutionary and ecological importance and the complex nature of the immune phenotype in the wild.

尽管我们在受控实验室条件下对脊椎动物免疫的机制理解正快速推进，但自然环境中免疫、感染与生存适合度之间的关联仍不甚明晰。抗体是获得性免疫应答的核心组分，体内循环的抗体水平反映了多种不同特异性的组成型与诱导型功能变体的复合特征——例如结合常见寄生虫、自身组织或新型非己来源抗原的抗体变体。本研究对圣基尔达群岛（St Kilda）未受人为干预的索艾羊（Soay sheep）种群中的成年雌性个体，测定了11种不同抗体类型的血浆浓度。抗体检测指标间的相关性总体呈正向但强度较弱，其中8项指标可独立预测个体体质量、圆线虫（strongyle）虫卵负荷以及后续越冬存活率。这些独立存在、且在部分情况下呈拮抗关系的关联，揭示了自然系统中影响生物体健康与生存适合度的重要多变量免疫学异质性。值得注意的是，本研究发现夏季抗线虫免疫球蛋白G（IgG）抗体水平与后续越冬存活率之间存在显著正向关联，这为自然环境下蠕虫（helminth）特异性免疫可提升生存适合度提供了罕见的实证依据。本研究结果既凸显了野生环境中免疫表型的进化与生态学重要性，也揭示了其复杂本质。