An Astrocyte

A Koosh Ball

When a brain is injured, cells called astrocytes change their shape (and probably their function too). An astrocyte is a cell in the brain that has many processes (think of a Koosh Ball) and these “arms” may help repair damage to your brain. In a “normal” injury, such as trauma or stroke, these astrocytes become enlarged and their arms grow in size and number. However, in an article published by PLosOne today Dr. Lowenstein, from Cedars-Sinai Medical Center and UCLA, and his collaborators demonstrate a new reaction by astrocytes to immunological insults in the brain (they looked at what happens during your body’s response to viral infections and autoimmunity in the brain).

This group of researchers demonstrates that when our own body’s cells attack astrocytes, instead of getting bigger, astrocytes, pull in all of their arms and form one large protrusion to interact with the attacking cell, called a T cell which is part of your immune system. This is a dramatic change in the shape of an astrocyte and may indicate a dramatic change in function as well. In the paper, the authors suggest that this change in shape may help fend off the attacking cell, either by blocking its way or even by engulfing the cell.

 Although there is only speculation at this point as to what this finding means, astrocytes have many functions in your brain; including protecting the barrier to your brain, helping transmit signals through your brain, promoting myelinating activity (health of your brain), as well as possibly regulating stem cells in your brain. All of these functions play a major role in your brain activity and, thus, your overall health. Understanding the interactions between immune cells and brain cells is an important part of treating immune responses in the brain, such as with Multiple Sclerosis, brain tumors, or viral infections in the brain (like West Nile Virus or HIV).

I know that this wasn’t a big-ticket news items today, but I work on the mechanisms of T cell activation during Multiple Sclerosis (an autoimmune disorder that attacks the myelin sheath protecting the nerves in your brain and spinal cord). So, I thought that this was pretty interesting and has many implications!