Thymocyte and TEC profiles in neonatal and adult thymus. (A) Average frequency of BrdU incorporation in cells from total thymi from 3 independent pooled litters of neonates and 3 individual adult animals (P = .01). (B) Representative FACS profiles of neonatal (left panel) and adult (right panel) thymocytes after gating on CD45⁺ cells. (C) Thymocyte distribution (mean and SD, shown as % of total CD45⁺ cells) from neonatal (n = 5) and adult (n = 3) mice. *P < .001; **P = .03. (D) H&E stain of sections of adult and neonatal thymus acquired according to “Morphologic and IF studies.” Lighter colored areas are medulla (M) and darker areas are cortex (C). (E) Frequency of TEC subsets, based on FACS profiles gated from CD45⁻MHCII⁺ cells. ■ indicates UEA-1⁺ mTECs; , Ly51⁺ cTECs. *P = .006; **P = .003. n = 3 pooled neonatal, and n = 3 individual adult samples. Error bars represent standard deviation.