Prendergast Brian J, Kampf-Lassin August, Yee Jason R, Galang Jerome, McMaster Nicholas, Kay Leslie M
Department of Psychology, Institute for Mind and Biology, University of Chicago, 940 E. 57th Street, Chicago, IL 60637, USA.
Brain Behav Immun. 2007 Nov;21(8):1096-108. doi: 10.1016/j.bbi.2007.05.004. Epub 2007 Aug 28.
Annual variations in day length (photoperiod) trigger changes in the immune and reproductive system of seasonally-breeding animals. The purpose of this study was to determine whether photoperiodic changes in immunity depend on concurrent photoperiodic responses in the reproductive system, or whether immunological responses to photoperiod occur independent of reproductive responses. Here we report photoperiodic changes in enumerative, functional, and behavioral aspects of the immune system, and in immunomodulatory glucocorticoid secretion, in reproductively non-photoperiodic Wistar rats. T-cell numbers (CD3+, CD8+, CD8+CD25+, CD4+CD25+) were higher in the blood of rats housed in short as opposed to long-day lengths for 10 weeks. Following a simulated bacterial infection (Escherichia coli LPS; 125 microg/kg) the severity of several acute-phase sickness behaviors (anorexia, cachexia, neophobia, and social withdrawal) were attenuated in short days. LPS-stimulated IL-1beta and IL-6 production were comparable between photoperiods, but plasma TNFalpha was higher in long-day relative to short-day rats. In addition, corticosterone concentrations were higher in short-day relative to long-day rats. The data are consistent with the hypothesis that photoperiodic regulation of the immune system can occur entirely independently of photoperiodic regulation of the reproductive system. In the absence of concurrent reproductive responses, short days increase the numbers of leukocytes capable of immunosurveillance and inhibition of inflammatory responses, increase proinflammatory cytokine production, increase immunomodulatory glucocorticoid secretion, and ultimately attenuate behavioral responses to infection. Seasonal changes in the host immune system, endocrine system, and behavior may contribute to the seasonal variability in disease outcomes, even in reproductively non-photoperiodic mammals.
白昼时长（光周期）的年度变化会引发季节性繁殖动物免疫和生殖系统的变化。本研究的目的是确定免疫方面的光周期变化是否依赖于生殖系统中同时发生的光周期反应，或者对光周期的免疫反应是否独立于生殖反应而发生。在此，我们报告了在生殖上无光周期反应的Wistar大鼠免疫系统的计数、功能和行为方面以及免疫调节性糖皮质激素分泌的光周期变化。与在长日照下饲养10周的大鼠相比，在短日照下饲养的大鼠血液中的T细胞数量（CD3 +、CD8 +、CD8 + CD25 +、CD4 + CD25 +）更高。在模拟细菌感染（大肠杆菌脂多糖；125微克/千克）后，短日照下几种急性期疾病行为（厌食、恶病质、新物恐惧和社交退缩）的严重程度有所减轻。脂多糖刺激的白细胞介素-1β和白细胞介素-6的产生在不同光周期之间相当，但长日照大鼠的血浆肿瘤坏死因子-α相对于短日照大鼠更高。此外，短日照大鼠的皮质酮浓度相对于长日照大鼠更高。这些数据与以下假设一致：免疫系统的光周期调节可以完全独立于生殖系统的光周期调节而发生。在没有同时发生的生殖反应的情况下，短日照会增加能够进行免疫监视和抑制炎症反应的白细胞数量，增加促炎细胞因子的产生，增加免疫调节性糖皮质激素的分泌，并最终减轻对感染的行为反应。宿主免疫系统、内分泌系统和行为的季节性变化可能导致疾病结果的季节性差异，即使在生殖上无光周期反应的哺乳动物中也是如此。
