Department of Zoology, Institute of Ecology and Earth Sciences, Tartu University, Vanemuise 46, 51014 Tartu, Estonia.
Exp Parasitol. 2011 Mar;127(3):651-7. doi: 10.1016/j.exppara.2010.12.004. Epub 2010 Dec 19.
Allocation trade-offs of carotenoids between their use in the immune system and production of integumentary colouration have been suggested as a proximate mechanism maintaining honesty of signal traits. We tested how dietary carotenoid supplementation, immune activation and immune suppression affect intensity of coccidian infection in captive greenfinches Carduelis chloris, a passerine with carotenoid-based plumage. Immune activation with phytohaemagglutinin (PHA) decreased body mass among birds not supplemented with lutein, while among the carotenoid-fed birds, PHA had no effect on mass dynamics. Immune suppression with dexamethasone (DEX) induced loss of body mass and reduced the swelling response to PHA. DEX and PHA increased the concentration of circulating heterophils. Lutein supplementation increased plasma carotenoid levels but had no effect on the swelling response induced by PHA. PHA and DEX treatments did not affect plasma carotenoids. Immune stimulation by PHA suppressed the infection, but only among carotenoid-supplemented birds. Priming of the immune system can thus aid in suppressing chronic infection but only when sufficient amount of carotenoids is available. Our experiment shows the importance of carotenoids in immune response, but also the complicated nature of this impact, which could be the reason for inconsistent results in studies investigating the immunomodulatory effects of carotenoids. The findings about involvement of carotenoids in modulation of an immune response against coccidiosis suggest that carotenoid-based ornaments may honestly signal individuals' ability to manage chronic infections.
人们提出，将类胡萝卜素在免疫系统和体被颜色形成之间进行分配权衡，这可能是维持信号特征真实性的一个近因机制。我们测试了饮食中叶黄素补充、免疫激活和免疫抑制如何影响圈养绿翅金鹦哥（Carduelis chloris）体内球虫感染的严重程度，绿翅金鹦哥是一种具有类胡萝卜素羽色的雀形目鸟类。植物血球凝集素（PHA）的免疫激活使未补充叶黄素的鸟类体重减轻，而在补充类胡萝卜素的鸟类中，PHA 对体重动态没有影响。地塞米松（DEX）的免疫抑制导致体重减轻，并降低了对 PHA 的肿胀反应。DEX 和 PHA 增加了循环异嗜白细胞的浓度。叶黄素补充增加了血浆类胡萝卜素水平，但对 PHA 诱导的肿胀反应没有影响。PHA 和 DEX 处理均不影响血浆类胡萝卜素。PHA 对免疫系统的刺激抑制了感染，但仅在补充类胡萝卜素的鸟类中。因此，免疫系统的启动可以帮助抑制慢性感染，但前提是有足够的类胡萝卜素。我们的实验表明了类胡萝卜素在免疫反应中的重要性，但也表明了这种影响的复杂性，这可能是研究类胡萝卜素免疫调节作用时结果不一致的原因。关于类胡萝卜素参与调节对球虫病的免疫反应的发现表明，基于类胡萝卜素的装饰物可能真实地反映了个体管理慢性感染的能力。
