In multiple sclerosis (MS), macrophages and microglia play a dual role that could be used to treat this neurodegenerative disease. These cells promote inflammation that demyelinates neurons but also sweep away the debris of damaged myelin and produce neurotrophic factors that would allow its restoration. According to a group of scientists from the University of Hasselt in Belgium, damage or repair depends on a double switch that combines the action of two enzymes, one that desaturates and another that elongates fatty acids. By reducing the levels of these enzymes, phagocytic cells would replenish the myelin instead of engulfing it.