Roast Michael J, Aulsebrook Anne E, Fan Marie, Hidalgo Aranzamendi Nataly, Teunissen Niki, Peters Anne
Physiol Biochem Zool. 2019 Mar/Apr;92(2):140-151. doi: 10.1086/702310.
Investment in immune function can be costly, and life-history theory predicts trade-offs between immune function and other physiological demands. Environmental heterogeneity may constrain or change the optimal strategy and thereby alter baseline immune function (possibly mediated by stress responses). We tested several hypotheses relating variation in climatic, ecological, and social environments to chronic stress and levels of baseline innate immunity in a wild, cooperatively breeding bird, the purple-crowned fairy-wren (Malurus coronatus coronatus). From samples collected biannually over 5 yr, we quantified three indexes of constitutive innate immune function (haptoglobin/PIT54, natural antibodies, complement activity) and one index of chronic stress (heterophil-lymphocyte ratio; ). Using an information-theoretic and multimodel inference statistical approach, we found that habitat quality and social group size did not affect any immune index, despite hypothesized links to resource abundance and parasite pressure. Rather, short-term variation in temperature and rainfall was related to immune function, while overall differences between seasons were small or absent, despite substantial seasonal variation in climate. Contrary to our expectation, we found no evidence that physiological stress mediated any effects of short-term climatic variables on immune indexes, and alternative mechanisms may be involved. Our results may be interpreted from the perspective of reactive scope models, whereby predictive homeostasis maintains standing immune function relative to long-term demands, while short-term environmental change, being less predictable, has a greater influence on baseline immune function.
对免疫功能的投入可能代价高昂，而生活史理论预测免疫功能与其他生理需求之间存在权衡。环境异质性可能会限制或改变最优策略，从而改变基线免疫功能（可能由应激反应介导）。我们在一种野生的、合作繁殖的鸟类——紫冠细尾鹩莺（Malurus coronatus coronatus）中，检验了几个关于气候、生态和社会环境变化与慢性应激及基线先天免疫水平之间关系的假设。从5年中每半年采集的样本中，我们量化了组成性先天免疫功能的三个指标（触珠蛋白/PIT54、天然抗体、补体活性）和一个慢性应激指标（异嗜性粒细胞与淋巴细胞比率）。使用信息论和多模型推断统计方法，我们发现栖息地质量和社会群体规模并未影响任何免疫指标，尽管假设它们与资源丰度和寄生虫压力有关。相反，温度和降雨的短期变化与免疫功能有关，而尽管季节间气候存在显著变化，但季节间的总体差异很小或不存在。与我们的预期相反，我们没有发现生理应激介导短期气候变量对免疫指标产生任何影响的证据，可能涉及其他机制。我们的结果可以从反应范围模型的角度来解释，即预测性稳态相对于长期需求维持既定的免疫功能，而短期环境变化较难预测，对基线免疫功能有更大影响。
