关键词: 皮质酮, 血糖, 免疫功能, 瘦素, 黑线仓鼠

Abstract: Animals in temperate areas often show seasonal changes in immunity. In our study,seasonal variations in immune responses in female striped hamsters(Cricetulus barabensis) were examined to test the winter immunoenhancement hypothesis. Female hamsters were wild-captured in the autumn and winter of 2014 and in the spring and summer of 2015.The degree of the swelling in the footpad was measured after injecting phytohaemagglutinin(PHA),which is indicative of cellular immunity. Enzyme-linked immunosorbent assay(ELISA) was used to detect serum anti-KLH IgM and IgG concentration after injecting keyhole limpet haemocyanin(KLH),which reflects humoral immunity.Body mass,relative fatness,total body fat mass and blood glucose levels of the hamster increased during the summer,whereas body mass and total body fat mass decreased in the autumn.The number of total white blood cells(WBC) increased in the winter and spring and decreased in the summer,and phytohaemagglutinin(PHA) response which indicates the cellular immunity was lower in the summer than other seasons,while thymus and spleen mass had no seasonal changes.IgG titres elevated and IgM titres decreased after 5 days of KLH injection in the autumn compared to other seasons.Body fat mass and blood glucose had negative correlations with cellular immunity,but no correlations with IgG or IgM titres,implying that energy reserves affect cellular immunity but not humoral immunity in hamsters.Maximum leptin levels occurred in the spring,which were positively correlated with IgM levels but not with cellular immunity,indicating its boosting effect on humoral immunity and no effect on cellular immunity.Corticosterone levels were the highest in the winter and spring while the lowest during the autumn,which were positively correlated with IgG or IgM levels but not with cellular immunity,suggesting its enhancing effect on humoral immunity but no effect on cellular immunity. In summary,different components of the immune system showed distinct patterns of seasonal changes. The winter immunoenhancement hypothesis was supported by the results of seasonal changes in white blood cells,cellular immunity and IgG titres,but not by immune organs and IgM titres.

Key words: Corticosterone, Glucose, Immune function, Leptin, Striped hamsters(Cricetulus barabensis)