Food Restriction and Refeeding Have No Effect on Cellular and Humoral Immunity in Mongolian Gerbils (Meriones unguiculatus)

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Small mammals in the temperate area often face fluctuations in food availability. Changes in food availability may have a great influence on an animals' immunity, which is important to their survival. We tested the hypothesis that cellular and humoral immunity would be suppressed by food restriction and restored to control levels by refeeding in Mongolian gerbils Meriones unguiculatus. Forty adult male gerbils were randomly divided into food-restricted (80% of baseline food intake) and food ad lib. groups. Similarly, another 40 adult male gerbils were also randomly assigned to two groups: a group for which food was restricted for 36 d and then provided ad lib. and a group that was continuously fed ad lib. Half of the gerbils in each group were injected with phytohemagglutinin (PHA) and keyhole limpet hemocyanin solution to assess cellular and humoral immunity, respectively; the others were injected with sterile saline as control groups. Food-restricted gerbils had significantly lower body mass, body fat mass, dry thymus mass, wet and dry spleen mass, and serum leptin levels than those of the controls, whereas refeeding restored these parameters to the controls. Both food restriction and refeeding had no significant effect on PHA response indicative of cellular immunity, immunoglobulin G and immunoglobulin M concentrations, and white blood cells. We also found that food restriction decreased corticosterone levels in food-restricted gerbils, while refeeding increased corticosterone levels in refed gerbils compared with the controls. Our results suggest that cellular and humoral immunity were not affected by food restriction and refeeding in gerbils.