Demas G E, Nelson R J
Department of Psychology, Johns Hopkins University, Baltimore, MD 21218, USA.
J Biol Rhythms. 1998 Jun;13(3):245-52. doi: 10.1177/074873098129000084.
Many nontropical rodent species display seasonal changes in reproductive physiology and metabolism, as well as in immune function. Field studies of seasonal changes in immune function typically report decreased immune function in the short days of winter compared to summer; presumably, reduced immunity in winter reflects increased glucocorticoid secretion in response to environmental stressors. In contrast, laboratory studies of photoperiodic changes in immunity invariably demonstrate increased immune function in short compared to long days. Although the precise mechanisms regulating short-day enhancement of immune function are not known, it is hypothesized that increased immunity is due to the increased duration of melatonin secretion in short compared to long days. However, melatonin can act both directly (i.e, via melatonin receptors located on lymphatic tissue) and indirectly (i.e., via alterations in gonadal steroids) to affect immune function. The present study examined the effects of exogenous melatonin administration on both cell-mediated and humoral immune function in adult male deer mice (Peromyscus maniculatus), as well as the role of gonadal steroid hormones in mediating these effects. Mice either were castrated to remove circulating androgens or received sham operations and were implanted with empty capsules or capsules containing melatonin. Individual mice implanted with melatonin underwent reproductive regression and displayed enhanced splenocyte proliferation to the T-cell mitogen concanavalin A; antigen-specific serum immunoglobulin M production was unaffected by melatonin treatment. Castration had no effect on either cell-mediated or humoral immune function. Taken together, these results suggest that exogenous melatonin enhances cell-mediated, but not humoral, immune function in adult male deer mice and that this effect is independent of gonadal steroid hormones. These results are consistent with a direct effect of melatonin on immunity.
许多非热带啮齿动物物种在生殖生理、新陈代谢以及免疫功能方面都表现出季节性变化。关于免疫功能季节性变化的野外研究通常报告称，与夏季相比，冬季短日照时免疫功能会下降；据推测，冬季免疫力降低反映了对环境应激源作出反应时糖皮质激素分泌增加。相比之下，关于免疫功能光周期变化的实验室研究总是表明，短日照相比长日照时免疫功能增强。尽管调节短日照增强免疫功能的确切机制尚不清楚，但据推测，与长日照相比，短日照时免疫力增强是由于褪黑素分泌持续时间增加所致。然而，褪黑素可直接（即通过淋巴组织上的褪黑素受体）和间接（即通过性腺类固醇的改变）作用来影响免疫功能。本研究检测了外源性褪黑素给药对成年雄性鹿鼠（白足鼠）细胞介导免疫功能和体液免疫功能的影响，以及性腺类固醇激素在介导这些影响中的作用。对小鼠进行阉割以去除循环雄激素，或者进行假手术并植入空胶囊或含褪黑素的胶囊。植入褪黑素的个体小鼠出现生殖退化，对T细胞丝裂原刀豆球蛋白A的脾细胞增殖增强；褪黑素处理对抗抗原特异性血清免疫球蛋白M的产生没有影响。阉割对细胞介导免疫功能或体液免疫功能均无影响。综上所述，这些结果表明，外源性褪黑素可增强成年雄性鹿鼠的细胞介导免疫功能，但不增强体液免疫功能，且这种作用独立于性腺类固醇激素。这些结果与褪黑素对免疫的直接作用一致。
