A Preliminary Study On The Seasonal Changes And Mechanisms Of Immune Function In Black Hamsters

The striped hamsters(Cricetulus barabeniss)is the main agricultural rodent living in northern China.The northern part of China belongs to the northern temperate zone where seasons change is significant.The animal's survivability will change with seasons.The animal's immune system can protect the animals from the virus,bacteria,pathogens and other attacks that is essential for animal survival.meanwhile,it is one of the important indexes to reflect the survival ability of animals.In recent years,with the development of the whole biological thought,ecological immunology research continuosly,the changes and influence factors of animals immune function have becoming the important content of ecological immunology research.In this paper,we put the striped hamster as the main research object.We studied the changes of immunological function of striped hamsters under the condition of low temperature and restricted food or the condition of semi-natural seasonal change.In order to determine the changes of immune function of striped hamsters,we detected the immune organs(thymus and spleen),total number of white blood cells in blood,serum immunoglobulin(Ig)including immunoglobulin M(IgM)and immunoglobulin G(IgG)concentration,phytohaemagglutinin(PHA)reaction in footpad and cytokine concentration.we also examined the serum leptin and serum corticosterone concentrations in order to explore the reasons of immune changes.The main results and conclusions are as follows:1.Immune function showed seasonal changes in striped hamsters.PHA response indicative of cell-mediated immunity and the number of WBC are highest in winter and lowest in summer.However,natural immunity and IgG and IgM concentrations are the strongest in summer,indicating that the seasonal changes of different immune system components of striped hamsters are inconsistent.The different patterns of multiple immune indicators can help us to understand the seasonal survival pattern of Striped hamsters more comprehensively.In the experiment,in winter the weight of Striped hamsters,the highest concentration of leptin is also increased,but body fat content is reduced,which may increase the heat production and metabolic rate,the main function of humoral immunity is the combination of cells,however,the cellular immunity is to kill cells within the virus,winter humoral immunity decreased indicates that winter striped hamsters defense ability to reduce extracellular pathogens,which may lead to decreased ability to survive in winter,The concentration ofcorticosterone in striped hamsters increased significantly in winter,which may be related to the lower ambient temperature in winter.The increase of corticosterone concentration was the most stress response at low temperature environment.In the semi-natural state of striped hamsters adequate food,excluding precipitation,predation and other factors,in the wild conditions of the immune changes still need further study.2.Food restricted reduced the weight of striped hamsters,indicating that in the face of inadequate food resources,striped hamsters use of energy stored in the body to adapt to the shortage of energy harsh environment.The effect of food restriction on cell-mediated immune function and humoral immune function was not significantly affected.Although low temperature did not reduce the body weight of striped hamsters,decreased the body fat content,which may be related to the increase of caloric production.The energy stored in the body increases the production of heat to maintain body temperature,while causing increased blood glucose levels.Low temperature also reduces the production of antibodies,the immune process is a high energy consumption process,when most of energy used to heat,the immune capacity is limited,but the natural immune enhances,indicating that when humoral immunity is inhibited,in order to survive,only enhance natural immunity,can enhance the survivability.Low temperature and limiting interaction significantly increased the serum corticosterone concentration,and the stress hormone secretion of the black line hamster increased and the leptin content did not change under the effects of low temperature and limited food stress.