Partial removal of brown adipose tissue enhances humoral immunity in warm-acclimated Mongolian gerbils (Meriones unguiculatus)

Abstract

Temperate rodent species experience marked seasonal fluctuations in environmental temperatures. High thermoregulatory demands during winter usually weaken immune function. Brown adipose tissue (BAT) plays a crucial role in adaptive thermoregulatory process. Thus, we proposed the hypothesis that BAT might participate in the regulation of seasonal changes in immune function. The present study examined the trade-off between thermoregulation and immune function and the potential role of BAT in regulating seasonal changes in immune function in Mongolian gerbils. Specifically, surgical removal of interscapular BAT (34% of total BAT) was performed in male gerbils, and subsequently acclimated to either warm (23 ± 1 °C) or cold (4 ± 1 °C) conditions. Gerbils were then challenged with innocuous antigens and the immune responses were measured. Resting metabolic rate (RMR) and nonshivering thermogenesis (NST) were increased under cold conditions. However, the cost of thermoregulation during cold acclimation did not suppress T-cell mediated immunity and humoral immunity or decrease spleen mass, thymus mass and white blood cells. Partial removal of BAT significantly enhanced humoral immunity in warm-acclimated, but not in cold-acclimated gerbils. T-cell mediated immunity, white blood cells and immune organs were not affected by BAT removal under both warm and cold conditions. Collectively, our results imply that BAT has a suppressive effect on humoral immunity in warm-acclimated gerbils and differential effects of BAT on humoral immunity under different temperatures (e.g., summer and winter) might be benefit to their survival.