THAT'S SO HOT: The macrophage, an immune cell known for engulfing infected cells or pathogens, may also play a role in temperature regulation. PHOTO RESEARCHERS, DAVID M. PHILLIPS
K.D. Nguyen et al., "Alternatively activated macrophages produce catecholamines to sustain adaptive thermogenesis," Nature, 480:104-8, 2011.
Maintenance of body temperature in response to cold was thought to be the purview of the sympathetic nervous system. But now, Ajay Chawla at the University of California, San Francisco, and colleagues have demonstrated that the immune system–specifically macrophages–plays a critical role in turning fat stores into energy and heat.
The researchers found that brown fat–the heat-producing fatty tissue found mostly in babies and hibernators–contained higher numbers of macrophages than other tissue. So Chawla exposed mice to cold temperatures to see if the numbers of macrophages changed. Although there was no difference in number, the macrophages in the brown and white fat of the chilled mice were more active ...
