Prendergast Brian J, Hotchkiss Andrew K, Bilbo Staci D, Nelson Randy J
Departments of Psychology and Neuroscience, The Ohio State University, Columbus, Ohio 43210, USA.
Biol Reprod. 2004 Mar;70(3):813-20. doi: 10.1095/biolreprod.103.023408. Epub 2003 Nov 19.
Differential allocation of energy to reproduction versus host defense is assumed to drive the seasonal antiphase relation between peak reproductive function and immunocompetence; however, evidence supporting this assumption is only correlational. These experiments tested whether photoperiod affects immune responses to antigens in peripubertal Siberian hamsters, whether such activation of the immune system exacts energetic and reproductive costs, and whether such costs vary seasonally. Male Siberian hamsters were raised from birth in long (LD) or short days (SD), which respectively initiate or inhibit the onset of puberty. To elicit a specific immune response, hamsters were injected with a novel antigen (keyhole limpet hemocyanin [KLH]) as juveniles. Reproductive development was attenuated and body temperature was elevated in LD hamsters relative to saline-injected control animals. In contrast, KLH treatments affected neither thermoregulation nor reproductive development in photoinhibited SD hamsters. In experiment 2, juvenile male hamsters were challenged with bacterial lipopolysaccharide (LPS) in order to elicit an innate immune response. Febrile and anorexic responses to LPS were greater in reproductively stimulated LD hamsters relative to reproductively inhibited SD hamsters. LPS treatments attenuated somatic and testicular development in LD hamsters, but did not significantly affect circulating testosterone concentrations. In contrast, LPS treatments were without effect on somatic and reproductive development in SD hamsters. These experiments indicate that photoperiod affects antigen-specific antibody production, febrile responses to LPS, and sickness behaviors in juvenile Siberian hamsters, and that peripubertal activation of the immune system exacts energetic and metabolic costs that can diminish the magnitude of somatic and reproductive maturation in LD. The data also underscore the importance of seasonally dependent life history factors in assessing physiological tradeoffs.
能量在繁殖与宿主防御之间的差异分配被认为是导致生殖功能峰值与免疫能力呈现季节性反相位关系的原因；然而，支持这一假设的证据仅仅是相关性的。这些实验测试了光周期是否会影响青春期前西伯利亚仓鼠对抗原的免疫反应，免疫系统的这种激活是否会产生能量和生殖成本，以及这些成本是否会随季节变化。雄性西伯利亚仓鼠从出生起就饲养在长日照（LD）或短日照（SD）条件下，长日照分别启动或抑制青春期的开始。为了引发特异性免疫反应，幼年仓鼠被注射了一种新型抗原（钥孔血蓝蛋白[KLH]）。与注射生理盐水的对照动物相比，长日照仓鼠的生殖发育受到抑制，体温升高。相比之下，KLH处理对光抑制的短日照仓鼠的体温调节和生殖发育均无影响。在实验2中，幼年雄性仓鼠受到细菌脂多糖（LPS）刺激以引发先天性免疫反应。相对于生殖受抑制的短日照仓鼠，生殖受刺激的长日照仓鼠对LPS的发热和厌食反应更强。LPS处理抑制了长日照仓鼠的体细胞和睾丸发育，但对循环睾酮浓度没有显著影响。相比之下，LPS处理对短日照仓鼠的体细胞和生殖发育没有影响。这些实验表明，光周期会影响幼年西伯利亚仓鼠对抗原的特异性抗体产生、对LPS的发热反应以及疾病行为，并且青春期前免疫系统的激活会产生能量和代谢成本，这些成本会降低长日照条件下仓鼠体细胞和生殖成熟的程度。数据还强调了季节性依赖的生活史因素在评估生理权衡中的重要性。
