Bilbo S D, Dhabhar F S, Viswanathan K, Saul A, Nelson R J
Department of Psychological and Brain Sciences, The Johns Hopkins University, Baltimore, MD 21218, USA.
Psychoneuroendocrinology. 2003 Nov;28(8):1027-43. doi: 10.1016/s0306-4530(02)00122-1.
Sex differences in immune function are well documented. These sex differences may be modulated by social and environmental factors. Individuals of polygynous species generally exhibit more pronounced sex differences in immune parameters than individuals of monogamous species, often displaying an energetic trade-off between enhanced immunity and high mating success. During winter, animals contend with environmental conditions (e.g. low temperatures and decreased food availability) that evoke energetic-stress responses; many mammals restrict reproduction in response to photoperiod as part of an annual winter coping strategy. To test the hypothesis that extant sex and species differences in immune surveillance may be modulated by photoperiod, we examined leukocyte numbers in males and females of two closely related hamster species (Phodopus). As predicted, uniparental P. sungorus exhibited a robust sex difference, with total white blood cells, total lymphocytes, T cells, and B cells higher in females than males, during long days when reproduction occurs, but not during short days when reproduction usually stops. In contrast, biparental male and female P. campbelli exhibited comparable leukocyte numbers during both long and short days. To study sex differences in stress responses, we also examined immune cell trafficking in response to an acute (2 h) restraint stressor. During stressful challenges, it appears beneficial for immune cells to exit the blood and move to primary immune defense areas such as the skin, in preparation for potential injury or infection. Acute stress moved lymphocytes and monocytes out of the blood in all animals. Blood cortisol concentrations were increased in P. sungorus females compared to males at baseline (52%) and in response to restraint stress (38%), but only in long days. P. campbelli males and females exhibited comparable blood cortisol and stress responses during both long and short days. Our results suggest that interactions among social factors and the environment play a significant role in modulating sex and seasonal alterations in leukocyte numbers and stress responses.
免疫功能方面的性别差异已有充分记录。这些性别差异可能会受到社会和环境因素的调节。一夫多妻制物种的个体在免疫参数上通常比一夫一妻制物种的个体表现出更明显的性别差异，常常在增强免疫力和高交配成功率之间表现出精力上的权衡。在冬季，动物要应对诸如低温和食物供应减少等引发精力应激反应的环境条件；许多哺乳动物会根据光周期限制繁殖，作为年度冬季应对策略的一部分。为了验证现存的免疫监测中的性别和物种差异可能受光周期调节这一假设，我们检查了两种亲缘关系密切的仓鼠（黑线毛足鼠属）雄性和雌性的白细胞数量。正如所预测的，单亲的黑线毛足鼠在繁殖发生的长日照期间，雌性的总白细胞、总淋巴细胞、T细胞和B细胞数量高于雄性，表现出明显的性别差异，但在繁殖通常停止的短日照期间则没有。相比之下，双亲的坎氏毛足鼠雄性和雌性在长日照和短日照期间的白细胞数量相当。为了研究应激反应中的性别差异，我们还检查了对急性（2小时）束缚应激源的免疫细胞运输情况。在应激挑战期间，免疫细胞离开血液并转移到皮肤等主要免疫防御区域似乎是有益的，以应对潜在的损伤或感染。急性应激使所有动物的淋巴细胞和单核细胞从血液中移出。黑线毛足鼠雌性在基线时（52%）和对束缚应激反应时（38%）的血液皮质醇浓度比雄性高，但仅在长日照期间如此。坎氏毛足鼠雄性和雌性在长日照和短日照期间的血液皮质醇和应激反应相当。我们的结果表明，社会因素与环境之间的相互作用在调节白细胞数量和应激反应的性别及季节性变化中起着重要作用。
