Effect of temperature and food restriction on immune function in striped hamsters (Cricetulus barabensis)

Small mammals in the temperate area face seasonal fluctuations of temperature and food availability, both of which may influence their immune responses being critical to the survival. In the present study, we tested the hypothesis that low temperature and food restriction would suppress immune function in striped hamsters (Cricetulus barabensis). Thirty-seven adult male hamsters were randomly assigned into the warm (23±1°C) and the cold (5±1°C) groups, which were further divided into the fed and the food restricted groups, respectively. Body mass was not affected by cold stress, food restriction or the interactions of cold stress × food restriction. Cold stress decreased total body fat mass, hematological parameters including white blood cells (WBC), lymphocytes (LYMP) and neutrophilic granulocytes (GRAN), and immunoglobin (Ig) M titers after 5 days of injecting keyhole limpet haemocyanin (KLH). However, cold temperature increased bacterial killing capacity indicative of innate immunity and did not affect the masses of thymus and spleen, intermediate granulocytes (MID), phytohaemagglutinin (PHA) response and the levels of blood glucose, serum leptin. Corticosterone concentration was affected significantly by the interaction of cold stress × food restriction but not by cold stress or food restriction. Food restriction reduced thymus mass, but other immunological parameters including body fat mass, spleen mass, hematological parameters, innate immunity, PHA response, the titres of IgM and IgG, and the levels of blood glucose, serum leptin were all not affected by food restriction or the interaction of cold stress × food restriction. Innate immunity was positively correlated with leptin levels, whereas no significant correlations were observed among the levels of blood glucose, serum leptin, corticosterone and all the detected immune parameters. Our results showed that cold stress suppressed humoral immunity but enhanced innate immunity and did not affect cellular immunity in striped hamsters. Most immunological indices were not influenced by food restriction. Blood glucose, leptin and corticosterone could not interpret the changes of innate, cellular and humoral immunity upon cold stress or food restriction in striped hamsters.