Overactive Microglia
Much of the problem with brain inflammation during a bout with the flu centers on the actions of microglia – immune cells that circulate among the brain’s neurons. If you’ve been reading this newsletter for long, you know about microglia – the brain’s garbage collectors. They perform many tasks that, under normal circumstances, help maintain the neural networks linked to memory and reasoning. In their “quiet” normal state, these immune cells maintain the synapses between neurons – the areas where neurons pass messages to one another in the form of electrical and chemical signals. This exchange of information among neurons is central to forming thoughts, memories and emotions. But when you suffer the flu, your immune system sets off inflammatory signals in the body that activate immune cells to kill off the flu virus. Unfortunately, say researchers, while that inflammation is busy protecting the body from the invasion of the pathogens, a side effect is to put the microglia into an inflammatory reactive state that sets off “cognitive dysfunction associated with influenza infection.”1 In other words, your thinking is scrambled and your mood deteriorates. The effects of brain inflammation can include:- Depression: A study in England indicates that inflammation in brain tissue can increase your chances of depression because it limits the birth of new brain cells and speeds the death of existing brain cells. The researchers link this action to the release of the inflammatory protein IFN-α, a substance that activates immune cells.2
- Impaired thinking and learning: Research suggests that viral infections like the cold and flu interfere with neurotransmitters that facilitate communication among the brain’s neurons. These problems can persist even after the body fights off the virus.3
- Obsessive-compulsion-disorder (OCD): Tests in Canada show that brain inflammation in people with OCD is more than 30 percent higher than in people without OCD. Using brain imaging, the researchers found that OCD sufferers had microglia that were more active in six different brain areas that are believed to be involved in producing OCD symptoms.4
