Why does the immune system become less effective as we age? A new USC study published in BMC Biology offers fresh insights by examining a key immune cell type across tissues: macrophages.

Macrophages act as the body’s cleanup and maintenance crew. Found in nearly every tissue, they help fight infections, remove damaged cells, repair tissues and keep inflammation under control, acting as a first line of defense for the immune system. But like many cells in the body, macrophages change as we get older.

In this new study, researchers analyzed data from macrophages collected from different mouse tissues, including the brain, lungs, liver and other organs. By comparing younger and older animals, they uncovered common patterns of aging shared across many macrophage populations, as well as important differences depending on where the cells come from.