The beneficial effect of environmental modulation favoring M2 polarization can also be seen in human beings. The FDA-approved drug glatiramer acetate (GA), which has been shown to be useful in treating relapsing and remitting multiple sclerosis, works by inducing a Th1 to Th2 shift, resulting in the production of anti-inflammatory cytokines [97]. Even though changing the environment seems to be beneficial in alleviating symptoms for the relapsing and remitting type of multiple sclerosis, the majority of patients ultimately experience progressive disease, suggesting that the environment is not the only factor in controlling inflammation. Since multiple sclerosis is a chronic disease that takes many years to progress, the continuous long-term activation of microglia has the potential to alter microglial function, either by making them less responsive to anti-inflammatory signals or less adept at phagocytosis. This potential failure of microglia to perform their proper function is also shared by other neurodegenerative diseases characterized by persistent, long-term inflammation. One of the best examples of this is Alzheimer’s disease.
