For patients with multiple sclerosis, the flu can trigger a cascade of immune responses that can result in a relapse of the disease. A recent study sheds light on what may be happening in the brains of MS patients during upper respiratory infections.
 
University of Illinois researchers used a strain of laboratory mice that are genetically prone to developing an autoimmune attack of the brain and spinal cord. After the mice were exposed to influenza, the research team examined changes in the mice and their brains.
 
Exposure to the flu did induce an MS-like symptoms in some of the mice, even though the virus itself was not found in the brain. When they looked more closely, the researchers found an increase in glial activation in brains taken from flu-infected mice.
 
Certain types of glia cells are involved in calling immune cells – in this case, neutrophils, monocytes, and T-cells – to the brain. Glia may be sending the signal to immune cells using chemokines. The researchers found that one chemokine in particular, CXCL5, was elevated in the brains of mice infected with flu as well as in the cerebral spinal fluid of human MS patients during relapse. Despite knowing more about how immune cells are called to the brain during an upper respiratory infection, the team still can’t explain why the immune system attacks the brain.
 
Results of mouse model studies sometimes do not translate to humans and may be years away from being a marketable treatment. However, being able to identify a particular piece of the puzzle, such as CXCL5, could get the medical community closer to a drug intervention in the future, researchers said.
 
The findings were published in the Proceedings of the National Academy of Sciences.