Macrophages (Greek: big eaters, from Greek μακρος (makros) = large, φαγειν (phagein) = to eat) are white blood cells that engulf and digest cellular debris, foreign substances, microbes, and cancer cells, and they modulate the immune system (in particular microglia – macrophages) using pro-youthful signalling.
One such effort in 2016 sent mesenchymal stem cells to the area of damage and resulted in a reduction of plaques in Alzheimer’s mice, as these stem cells reduce inflammation and encourage pro-youthful function via intracellular signaling .
Recently, researchers showed that delivering fresh, functionally young macrophages to the brain results in removal of the plaques (misfolded proteins) associated with Alzheimer’s disease .
This means that brain aging is not a one-way process and suggests that we might be able to use our own rejuvenated macrophages to treat this horrific disease and other, similar diseases, including heart disease and Parkinson’s, which also involve plaque accumulation.
Introducing youthful macrophages and boosting their efficiency represents a plausible pathway to treating age-related diseases, and the research world is currently investigating the potential of a number of therapies that do this.
 Naaldijk, Y., Jaeger, C., Fabian, C., Leovsky, C., Blüher, A., Rudolph, L., … & Stolzing, A. (2016). Effect of systemic transplantation of bone marrow‐derived mesenchymal stem cells on neuropathology markers in APP/PS1 Alzheimer’s mice. Neuropathology and applied neurobiology.
 Daria, A., Colombo, A., Llobera, G., Hampel, H., Willem, M., Liesz, A., … & Tahirovic, S. (2016). Young microglia restore amyloid plaque clearance of aged microglia. The EMBO Journal, e201694591.