Microglia

Microglia are the resident immune cells of the brain and spinal cord, constantly surveying their surroundings and responding to injury, infection and cellular debris.

Unlike most brain cells, microglia descend from early embryonic immune precursors and renew themselves locally rather than from bone marrow. In a healthy brain they extend fine processes that touch synapses and prune unneeded connections during development. When they sense damage, they change shape, migrate toward the site, engulf debris and release cytokines, reactive oxygen species and growth factors. This activated state is protective in the short term but, when sustained, contributes to the chronic neuroinflammation seen in neurodegenerative diseases.

Microglia express CB2 receptors, which rise in number when the cells activate, and they carry other targets such as PPAR-gamma. Researchers study them with imaging tracers and in postmortem tissue. CBD has been reported to modulate microglial activation in cell and rodent experiments, but this remains preclinical work with no established application in people or animals.