The invention is directed to methods of promoting myelin formation in central nervous system (CNS) tissue in a subject in need thereof, the method comprising administering to the subject a therapeutically effective amount of interleukin-4 induced gene 1 (IL4-i1) protein. The invention is also directed to methods of monitoring the progression of conditions marked by an impairment of myelin formation in the CNS comprising assessing the levels or activity of IL4-i1 in activated macrophages obtained from the subject.
