Microglia: the brain matter recyclers
Microglia are macrophages that reside in the brain and central nervous system; they respond to inflammations and infections of the brain and spinal cord. The blood-brain barrier protects the central nervous system from most pathogens, but viruses such as herpes and HIV can breach the barrier and infect the brain and nerves. In other parts of the body, macrophages summon T- and B-cells, but in the brain and spinal cord microglia have no backup and have to defend against pathogens on their own.
Microglia also devour damaged neurons and plaques. Microglia also transform some of their digested waste into nutrients that they feed back to neurons. “From a waste point of view, some of the material can be recycled and reused,” says Chang, adding that microglia secrete the growth factors which “help neurons grow.”
Researchers have an ongoing debate about whether microglia mitigate or aggravate neurodegeneration. Studies have found that microglia can destroy the amyloid beta protein implicated in formation of damaging Alzheimer’s plaques. At the same time, microglia can secrete neurotoxins that cause inflammation, which can kill neurons.
Source: Meet Your Body’s Death Eaters - Issue 7: Waste - Nautilus