Subpopulations of human fetal thymocyte and circulating naïve T cells were obtained through FACS sorting, including CD3-CD4+CD8- intrathymic T progenitor cells (ITTP), CD3intCD4+CD8+ "double positive" thymocytes (DP), CD3highCD4+CD8- "single positive" thymocytes (SP4), CD3+CD4+CD8-CD45RA+CD62L+ naïve T cells from cord blood (CB4+), and CD3+CD4+CD8-CD45RA+CD62L+ naïve T cells from adult blood (AB4+). Keywords = Microarray Keywords = gene expression Keywords = thymocytes Keywords = naïve CD4+ T cell Keywords = recent thymic emigrants