Data from: Age-related declines in immune response in a wild mammal are unrelated to immune cell telomere length

Senescence has been hypothesised to arise in part from age-related declines in immune performance, but the patterns and drivers of within-individual age-related changes in immunity remain virtually unexplored in natural populations. Here, using a long-term epidemiological study of wild European badgers (Meles meles), we (i) present evidence of a within-individual age-related decline in the response of a key immune-signalling cytokine, Interferon-gamma (IFNγ), to ex vivo lymphocyte stimulation, and (ii) investigate three putative drivers of individual variation in the rate of this decline (sex, disease and immune-cell telomere length; ICTL). That the within-individual rate of age-related decline markedly exceeded that at the population level suggests that individuals with weaker IFNγ responses are selectively lost from this population. IFNγ responses appeared to decrease with the progression of bovine tuberculosis infection (independent of age) and were weaker among males than females. However, neither sex nor disease influenced the rate of age-related decline in IFNγ response. Similarly, while ICTL also declines with age, variation in ICTL predicted neither among- nor within-individual variation in IFNy response. Our findings provide evidence of within-individual age-related declines in immune performance in a wild mammal and highlight the likely complexity of the mechanisms that generate them.衰老的部分成因已被假说为免疫功能随年龄增长而衰退，但在自然种群中，个体内部免疫功能随年龄变化的模式与驱动因素，迄今几乎仍未得到探索。本研究依托针对野生欧洲獾（Meles meles）的长期流行病学调查，（1）提供了关键免疫信号细胞因子干扰素-γ（Interferon-gamma, IFNγ）在体外淋巴细胞刺激下的应答存在个体内部随年龄增长而衰退现象的证据；（2）探究了该衰退速率存在个体差异的三个潜在驱动因素：性别、疾病状态与免疫细胞端粒长度（ICTL）。个体内部的年龄相关性衰退速率显著高于种群水平的衰退速率，这提示干扰素-γ应答较弱的个体在该种群中遭到选择性淘汰。干扰素-γ应答随牛结核病感染进程（与年龄无关）呈下降趋势，且雄性个体的应答强度弱于雌性个体。但性别与疾病状态均未对干扰素-γ应答的年龄相关性衰退速率产生显著影响。类似地，尽管免疫细胞端粒长度（ICTL）同样随年龄增长而缩短，但其变异既无法预测种群间的干扰素-γ应答变异，也无法预测个体内部的该应答变异。本研究的发现为野生哺乳动物中存在个体内部免疫功能随年龄增长而衰退的现象提供了实证依据，并揭示了驱动该现象的潜在机制大概率具有复杂性。