The article I found was from the Scientific American and is entitled "The Rise of Microglia". This article describes the new research that shows that the microglia are involved in both development and disease. Microglia are also known as the immune cells of the brain and are now being found to play a role in the developing brain and implicated in the developmental and neurodegenerative disorders. In a diseased brain microglia find the injured neurons and strip away the synapses between the neurons. However, researches discovered that microglia were also active in healthy brains- this led to questions and even more research.
New research shows that the protective tag that keeps the healthy cells from being destroyed by the immune system may also protect the cells from the microglia. A doctoral candidate (Emily Lehrman) found that the protective tag is highly pronounced in the visual system in mice five days after birth which is also when the synaptic pruning peaks. When this protective tag was removed in the mice there was excess engulfment by mircroglia and over pruning of the neuronal connections. Another researcher, Cornelius Gross, found that removing the receptor for fractalkine (a key molecule in neuron-microglia signaling) created many weak synaptic contacts caused by deficient synaptic pruning during the development in the hippocampus.
As I previously said, when the brain has an injury or incurs a disease the microglia surround the damaged areas and eat up the dying cells. The article discusses how the microglia may be delaying the progression of the diseases by clearing cellular debris, but, how there is a possibility that the microglia are contributing to the disease. New evidence is leading to the possibility that microglia pruning pathways that are seen in early development may be reactivated later in life- which may cause disease. Unpublished data suggests that microglia are involved in the early stages of Alzheimer's, and that blocking microglia's effects may reduce the synapse loss in those with Huntington's disease. This research has HUGE potential for the future of these diseases and is very exciting!
http://www.scientificamerican.com/article/rise-of-the-microglia/
I found this post to be fairly interesting, because I previously only thought of microglia as being the "garbage collectors" of the brain. I knew they worked to eliminate decayed neurons from nervous tissue, but for some reason I never connected this function with pruning. Although after reading this blog post, the connection does make sense. What was especially interesting, however, is how the same microglial pathways formed in the developmental pruning process can be reactivated later in life. This is a remarkable discovery, as we can now begin to research how to slow down or altogether block microglia from reactivating on the old pathways. Perhaps, researchers will be able to use this information in order to create preventative treatment for diseases such as Alzheimer's.
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