The Journal of Experimental Medicine
email: [email protected] Phone: (405)271-7209;Fax: 271-8569; Research Foundation,825NE13th St.,OklahomaCity,OK73104. Address correspondencetoK.Mark Coggeshall,OklahomaMedical markers (Lin vivo assaysusingsortedpopulationsthatlackalllineage mitted precursorcellscanbedetectedinvitroand in (1, 2).InadditiontoexpressionofRAG,lymphoid-com- showed minimalcapacitytodevelopintoanotherlineage or myeloid-committedprogenitors,definedasabove, by expressionofRAG.Sortedpopulationslymphoid- lymphoid andnaturalkillercelllineages(2)ismarked tors. Theotherpopulationhasthecapacitytoformall lineages (1)andismarkedbylowexpressionofIgGrecep- tion hasthecapacitytoformmyeloidandmegakaryocyte that givesrisetotwoprecursorpopulations.Onepopula- Hematopoietic cellsdevelopfromaprimitivestemcell Introduction