The insulating layer around nerve fibres breaks down as mice age, and this could lead to immune dysfunction.
The myelin layer coats nerves to speed up signal transmission. Mikael Simons at the Max Planck Institute for Experimental Medicine in Göttingen, Germany, and his colleagues used electron microscopy to study the brains of mice. They found that the amount of myelin fragments increased with age and that the pieces were taken up by immune cells in the brain called microglia, which engulf debris and foreign materials. During this process, insoluble fatty aggregates accumulated in the microglia and the ability of the cells to take up material declined.
The authors suggest that microglia become overwhelmed with the growing amount of myelin debris, making them less able to function in the ageing brain.
Nature Neurosci. http://dx.doi.org/10.1038/nn.4325 (2016)