| Seasonal changes can cause variations in animal immunity.The Winter immunoenhancement hypothesis states that animals’ immunity will increase in winter to cope with the stress caused by low temperature and food shortages.There are differences in the immune function of animals of different genders.The immunocompetence handicap hypothesis holds that the maintenance of secondary sexual characteristics in male animals is at the expense of immune function.That testosterone suppresses the immunity of animals is the basis for this hypothesis.In this thesis,ICR mice were taken as the research objects.The seasonal changes of immunity and behavior and whether there were gender differences were investigated by detecting immune and behavioral indicators such as innate immunity,humoral immunity,cellular immunity,and cytokines in different seasons.The winter immunoenhancement hypothesis was tested.In order to understand the role of sex hormones in immunity and behavior,ICR mice and Djungarian hamsters(Phodopus sungorus)were taken as the research objects.Their immune function and behavioral indicators were detected after testis removal and testosterone supplementation to understand the role of testosterone in immunity and behavior.The immunocompetence handicap hypothesis was tested too.The main results obtained are as follows:1.The spleen weight of mice in winter is lower than that in other seasons,and the bactericidal ability of serum in spring and summer is higher than that in autumn and winter;the concentration of Immunoglobulin(Ig G)10 in male mice is higher in summer than in other seasons;The Phytohemagglutinin(PHA)response at 12 h and48h in autumn was higher than that in spring and winter,and these results did not support the hypothesis of immune function in winter.The Ig G 10 concentration in female mice was highest in winter and lowest in spring,supporting this hypothesis.The fresh weight of female thymus and spleen was higher than that of male,and the serum bactericidal capacity and Ig G 10 concentration of female mice in winter were higher than those of male.These results indicated that female mice had higher innate immunity and humoral immunity than males.There was no gender difference in complement C3 levels,while in spring the PHA 6h response of male mice was higher than that of females.There was no seasonal variation in the levels of blood glucose,leptin,corticosterone,and testosterone in the mice,and there was no gender difference.In the open field experiment,grooming times of mice was more in spring than in summer and autumn,upright times is more in summer than in spring and winter,and horizontal crossing times in autumn is more than in spring and winter.In autumn,center zone stay time of females is more than males,and males had more grooming times in summer and autumn,and more stool count in spring and summer than females.2.Removal of the testis did not affect the weight,blood glucose and corticosterone levels of the mouse thymus and spleen,but decreased the testosterone and leptin levels of the mice.In addition,testis removal enhanced the serum bactericidal capacity,Ig G 5,Ig G 10,and Interleulin-2(IL-2)levels in mice;these results indicated that innate and humoral immune functions in mice after orchiectomy were increased,supporting the immunocompetence handicap hypothesis.Testosterone supplementation did not affect blood glucose and corticosterone levels in mice,but decreased PHA responses at 6h,12 h,and 24 h,indicating that testosterone has an inhibitory effect on cellular immunity,supporting this hypothesis.Testosterone levels were negatively correlated with Ig G 5,IL-2 levels,thymus,and spleen,suggesting that testosterone has inhibitory effects on these immune markers.Testicular removal and testosterone supplementation had no effect on the levels of Interleukin-4(IL-4),Tumor necrosis factor-α(TNF-α),and Interferon-gamma(IFN-γ),which do not support the immunocompetence handicap hypothesis.Resection of the testis increased the center zone stay time before injection in mice,increased the times of grooming on day 30,and decreased the times of upright on day 30.3.Testis removal did not affect the body weight,body temperature,thymus and spleen fresh weight,blood glucose and corticosterone levels,IL-4,TNF-α and IFN-γlevels of Djungarian hamsters,but increased serum bactericidal ability,Ig G 5 and IL-2 levels,decreased PHA response and testosterone and leptin levels at 6h,12 h and24h.Testosterone supplementation increased testosterone levels in Djungarian hamsters but did not affect body weight,body temperature,thymus and spleen weights,blood glucose and corticosterone levels,IL-4,TNF-α and IFN-γ levels,results that do not support the immunocompetence handicap hypothesis,testosterone supplementation reduced IL-2 levels,supporting this hypothesis.Testosterone levels were negatively correlated with serum bacterial killing capacity,Ig G 5,and IL-2levels,suggesting that testosterone may inhibit humoral immunity.Testicular removal increased the times of upright before injection and stay time on day 15,and decreased times of grooming on day 15 and center sone stay time on day 30;supplemental testosterone increased horizontal crossing times on day 15.In conclusion,the seasonal variation patterns of different immune components in mice are different,and there are gender differences in immune function,as well as seasonal changes and gender differences in their behaviors.Testis removal and testosterone supplementation had different effects on the immune function of mice and Djungarian hamsters.Testosterone suppressed innate immunity,humoral immunity and cellular immunity in mice,but enhanced cellular immunity in hamsters.Testosterone increased exercise and reduces anxiety in mice and hamsters. |
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