食物限制对黑线仓鼠免疫功能的影响

温带地区小型哺乳动物经常面临着食物资源的波动。食物对动物的免疫功能具有重要影响。将19只成年雄性黑线仓鼠(Cricetulus barabensis)随机分为自由取食组(n=9)和限食组(n=10)。注射植物血球凝集素(PHA)来测定细胞介导的免疫反应,用匙孔血蓝蛋白(KLH)免疫动物,然后测定抗KLH抗体的浓度以反映其体液免疫功能。旨在检验食物限制是否会抑制黑线仓鼠的细胞免疫和体液免疫功能。结果发现,与对照组相比,限食组黑线仓鼠具有较低的体重、体脂、脾脏鲜重、血清瘦素水平、免疫球蛋白Ig G和Ig M浓度。而限食对胸腺鲜重、白细胞数、皮质酮水平以及PHA反应没有显著影响。结果表明黑线仓鼠免疫系统的不同成分对限食反应存在差异,在食物资源短缺时,黑线仓鼠防御细胞外病原体的能力降低,从而导致生存能力的下降。

Effect of food restriction on immune function in the striped hamster (Cricetulus barabensis)

The immune system protects animals against environmental pathogens, and hence it plays an important role in their survival and fitness. However, immune function is influenced by many factors including food availability. Small mammals in the temperate zone often face fluctuations in food availability, which is important to their survival. Changes in food availability may have a great influence on an animals'' immunity. Some investigators have examined the effect of reduced food availability (i.e., food restriction) on the immune function in small rodents, but their results are often inconsistent. Food restriction could depress, enhance or have no effect on immunity in different species. In order to clarify the discrepancy between results, the striped hamster (Cricetulus barabensis) was used to examine the effect of food restriction on its immune function. The striped hamster is a major pest rodent in northern China. It is granivorous, nocturnal and feeds mainly on plant stems and leaves during summer and forages crop seeds in winter. The climate is arid and characterized by warm and dry summers and cold winters. Thus, the species experiences great seasonal fluctuations in temperature, photoperiod as well as food quality and availability. The question we focused on in the present study was how the immune function would vary in the face of reduced food availability for hamsters. Nineteen adult male hamsters were randomly divided into the fed ad libitum group (Fed, n=9) and food restricted group (FR, n=10) (90% of baseline food intake). The course of food restriction was 21 days. Hamsters were injected with phytohaemagglutinin (PHA) and keyhole limpet haemocyanin (KLH) solution to assess cellular and humoral immunity, respectively. Our goal was to test whether food restriction would suppress cellular and humoral immunity in striped hamsters. Body mass in the FR group decreased significantly after 21 days of food restriction, whereas body mass in the Fed group did not change significantly. Body mass in the FR group was significantly lower than that of the Fed group after 10 days of food restriction. Food restriction significantly reduced perirenal fat, perirenal fat content, retroperitoneal fat, total body fat, and wet spleen mass in the FR group compared with the Fed group. However, it had no significant effect on the wet thymus mass or white blood cells. Immunoglobulin (Ig) G and IgM concentrations were reduced significantly in the food restricted hamsters in contrast with the Fed control group, which indicated the suppressive role of food restriction on humoral immunity. PHA response did not differ between the two groups, suggesting cellular immunity was not influenced by food restriction. Food restricted hamsters had significantly lower serum leptin levels than that of the control group, while corticosterone levels were not affected by food restriction. Taken together, our results suggest that different components of the immune system respond differently to food restriction in striped hamsters. Humoral immunity was suppressed in food restricted hamsters, which might be due to their lower body fat mass and lower leptin levels. In the face of food shortage, striped hamsters might be more prone to extracellular pathogens and their survival capability would decrease.