Evidence for age-related changes in innate and adaptive immune responses is increasing in wild populations. Such changes have been linked to fitness, and knowledge of the factors driving immune response variation is important for understanding the evolution of immunity. Age-related changes in immune profiles may be owing to factors such as immune system development, sex-specific behaviour and responses to environmental conditions. Social environments may also contribute to variation in immunological responses, for example, through transmission of pathogens and stress arising from resource and mate competition. Yet, the impact of the social environment on age-related changes in immune cell profiles is currently understudied in the wild. Here, we tested the relationship between leukocyte cell composition (proportion of neutrophils and lymphocytes [innate and adaptive immunity, respectively] that were lymphocytes) and age, sex and group size in a wild population of European badgers (Meles meles). We found that the proportion of lymphocytes in early life was greater in males in smaller groups compared to larger groups, but with a faster age-related decline in smaller groups. By contrast, the proportion of lymphocytes in females was not significantly related to age or group size. Our results provide evidence of sex-specific age-related changes in immune cell profiles in a wild mammal, which are influenced by the social environment.

在野生种群中，先天性和适应性免疫反应中与年龄相关的变化的证据正在增加。这种变化与适应性有关，因此了解驱动免疫应答变异的​​因素对于理解免疫的进化很重要。免疫谱中与年龄相关的变化可能是由于诸如免疫系统发育，性别特异性行为和对环境条件的反应等因素引起的。社交环境也可能导致免疫应答发生变化，例如，通过病原体的传播以及资源和配偶竞争而产生的压力。然而，目前在野外还研究了社会环境对与年龄相关的免疫细胞分布变化的影响。这里，狗獾）。我们发现，与较大的群体相比，较小的群体中男性早期生命中淋巴细胞的比例更高，而较小的群体中与年龄相关的下降更快。相比之下，女性中淋巴细胞的比例与年龄或群体规模没有显着相关。我们的结果提供了证据，证明受社会环境影响的野生哺乳动物免疫细胞特征与性别相关的年龄相关变化。