Interferon-gamma (IFN-gamma) can induce class I major histocompatibility complex (MHC) antigen (H-2) expression on virtually all neuroepithelial cells isolated from embryonic day 9 (E9) mice. However, a subpopulation of cells become refractory to H-2 induction (H-21-) by E10 and the percentage of H-2 noninducible cells increases during development. Cell sorting, by flow cytometry or magnetic bead immunoselection, has shown that H-21- cells give rise exclusively to neuronal cells, and by E12, the majority of the neuronal progenitors are found within this population. It has also been found that 98% of the H-21- also express the neuron-associated marker, A2B5. Cells of the glial cell lineage retain the ability to express class I antigens throughout development. From these studies, it is clear that the neuroepithelium contains cells committed to the neuronal cell lineage as early as E10 in the mouse.