Human immune cells in blood can be converted directly into functional neurons in the laboratory in about three weeks with the addition of just four proteins, researchers at the Stanford University School of Medicine have found. The conversion occurs with relatively high efficiency — generating as many as 50,000 neurons from 1 milliliter of blood — and it can be achieved with fresh or previously frozen and stored blood samples, which vastly enhances opportunities for the study of neurological disorders such as schizophrenia and autism. A paper describing the findings was published online June 4 in the Proceedings of the National Academy of Sciences. Wernig is the senior author. Former postdoctoral scholar Koji Tanabe, PhD, and graduate student Cheen Ang are the lead authors.