1. A method of producing neuronal progenitor cells comprising: dissecting primarily white matter from adult human brain tissue; isolating a population of neural progenitor cells from the dissected adult human brain tissue white matter, said isolating comprising immunoseparating the human white matter progenitor cells by extracting cells expressing immunoreactivity for A2B5; permitting the isolated population of neural progenitor cells from the dissected adult human brain tissue white matter to differentiate to neuronal progenitor cells, in the presence of one or more growth factors; and recovering an enriched population of neuronal progenitor cells after said permitting the isolated population of neural progenitor cells from the dissected adult human brain tissue white matter to differentiate to neuronal progenitor cells.