Data from: Immune challenges decrease biliverdin concentration in the spleen of Northern Bobwhite Quail, Colinus virginianus

Most antioxidants have multiple functions; in addition to minimizing oxidative damage, many antioxidants have immune-modulating properties. For example, biliverdin is produced in the liver and spleen from the breakdown of heme, and has putative immune-suppressing and antioxidant properties. However, the majority of these properties have been investigated in vitro or in mammalian models, in which biliverdin reductase converts virtually all biliverdin to bilirubin. Thus, biliverdin’s physiological roles remain largely untested. Here, we investigated whether biliverdin has immunomodulating roles by injecting Northern Bobwhite quail (Colinus virginianus) with either a vehicle control, lysed and rinsed pig red blood cells (pRBC) that contain erythrocyte antigens but no heme, or intact pRBC that contain both erythrocyte antigens and hemoglobin, thus increasing the amount of heme that can be converted to biliverdin. We then quantified hemagglutination and hemolysis ability, and biliverdin concentration in the liver and spleen, on 3, 6, and 9 days post-injection. We found that hemagglutination was greater in individuals that received intact pRBC, but not in those injected with heme-removed pRBC, demonstrating that biliverdin does not suppress immune function at this dosage. Biliverdin levels of liver and spleen were correlated within individuals, suggesting organism-level variation in biliverdin production. Lastly, individuals injected with intact pRBC had a reduced biliverdin concentration in the spleen, suggesting that immune challenges may reduce biliverdin production or accumulation. This initial investigation demonstrated that biliverdin may have more nuanced physiological roles than previously reported, supporting the value of further investigations into the physiology of biliverdin.绝大多数抗氧化剂均具备多重功能：除减轻氧化损伤外，诸多抗氧化剂还具有免疫调节特性。例如，胆绿素（biliverdin）由血红素（heme）在肝脏与脾脏中分解产生，被认为具有免疫抑制与抗氧化特性。然而，此类特性的绝大多数相关研究均在体外环境或哺乳动物模型中开展——在这类模型中，胆绿素还原酶几乎可将所有胆绿素转化为胆红素（bilirubin）。因此，胆绿素的生理功能在很大程度上仍未得到验证。本研究通过向北美山齿鹑（Colinus virginianus）分别注射溶剂对照、经裂解并冲洗的猪红细胞（pRBC，该类细胞仅含红细胞抗原而不含血红素），以及同时含有红细胞抗原与血红蛋白的完整猪红细胞，以提升可转化为胆绿素的血红素含量，以此探究胆绿素是否具备免疫调节功能。随后，我们分别在注射后第3、6、9天，对受试个体的血凝反应、溶血反应能力以及肝脏与脾脏内的胆绿素浓度进行定量检测。研究结果显示，接受完整猪红细胞注射的个体血凝反应更强，但经去除血红素的猪红细胞注射的个体未出现该现象，这表明该剂量下的胆绿素并不会抑制免疫功能。个体肝脏与脾脏中的胆绿素水平呈显著相关，提示胆绿素的生成存在个体水平的差异。最后，接受完整猪红细胞注射的个体脾脏内胆绿素浓度有所降低，这表明免疫刺激可能会抑制胆绿素的生成或积累。此项初步研究表明，胆绿素的生理功能可能比此前报道的更为复杂精细，这也为后续开展胆绿素生理学相关研究提供了支撑。