Key points from article :
Eosinophils are white blood cells that are typically found circulating in the bloodstream but are also resident in belly fat.
They contain a package of around 200 granules of enzymes and proteins and burst open to release their payloads when triggered.
In healthy people, between 1-5% of all white blood cells in the body are eosinophils.
Eosinophils resident in belly fat appear to help to regulate and maintain local immune system homeostasis.
As we age, the number of eosinophils present in the belly fat declines, and pro-inflammatory macrophage rise.
Therefore, belly fat becomes a source of pro-inflammatory signals.
Scientists transferred eosinophils from young mice into old mice, which reversed both local and systemic inflammation.
The mice experienced an improvement to physical fitness and their vaccination response - suggesting that the immune system was rejuvenated.
Research by University of Bern published in Nature Metabolism.