Dissertation Research: Hormonal regulation of immune function in seasonally-breeding birds

论文研究：季节性繁殖鸟类免疫功能的激素调节在许多脊椎动物中，类固醇激素睾酮(T)被认为对健康有双向影响。T在雄性的繁殖和攻击行为中起着重要作用，并促进了许多第二性征的发展，这对雌性的选择很重要。另一方面，高水平的T被认为会抑制免疫功能。许多对鸟类的研究发现T抑制免疫系统的某些成分，但尚不清楚这种机制是通过直接还是间接途径发生的。本研究的主要目的是了解这些途径在调节西北宋雀（Melospiza melodia morphna）和白冠雀（Zonotrichia leucophrys） t诱导免疫抑制中的作用。实验中，许多鸟类体内的T水平升高会改变其他激素的水平，如皮质酮和雌二醇，它们也能调节免疫力。因此，鸟类的免疫功能可能是通过这些中间激素而不是由睾酮直接改变的。将对这两个物种进行一系列实验，包括使用激素植入和/或药物阻滞剂来梳理这些对生理和行为免疫功能的直接和间接影响。这些研究将为季节性繁殖鸟类的激素免疫调节提供新的见解，并调和现有的理论，这些理论认为T在调节雄性脊椎动物免疫能力和繁殖成功之间的权衡中起直接作用。

DISSERTATION RESEARCH:HORMONAL REGULATION OF IMMUNE FUNCTIONIN SEASONALLY-BREEDING BIRDSNoah T. Owen-Ashley & John C. WingfieldUniversity of Washington, Seattle The steroid hormone testosterone (T) is thought to have bidirectional effects on fitness in many vertebrates. T is important in orchestrating reproductive and aggressive behavior in males, and promoting the development of many secondary sex characters important for female choice. On the other hand, high levels of T are thought to suppress immune function. Many studies in birds have found that T suppresses some component(s) of the immune system, but it is not known if this mechanism occurs through direct or indirect pathways. The main goal of this research is to understand the contributions of these pathways in regulating T-induced immunosuppression in the Northwestern Song Sparrow (Melospiza melodia morphna) and the White-crowned Sparrow (Zonotrichia leucophrys). Experimental elevation of T in many bird species alters the levels of other hormones, such as corticosterone and estradiol, which also regulate immunity. Therefore, avian immune function may be altered through these intermediary hormones, rather than by testosterone directly. A suite of experiments will be conducted on both species involving the use of hormone implants and/or pharmacological blockers to tease apart these direct and indirect effects on physiological and behavioral immune function. These studies will provide new insights into hormonal regulation of immunity in seasonally-breeding birds, and reconcile existing theories which assume a direct role of T in regulating a tradeoff between immunocompetence and reproductive success in male vertebrates.