RTEs are more abundant in neonates than adults. Thymocytes from neonatal (7-day-old) and adult (6- to 8-week-old) RAG2p-GFP^+/− mice were stained for CD4 and CD8. (A) Gates were set on DN and CD4⁺ SP cells. (B) GFP expression within the gated DN thymocyte population was then used to define GFP^hi RTEs, GFP^lo intermediates, and GFP⁻ resident cells. The percentage of RTEs, intermediate, and resident cells among CD4⁺ SP thymocytes (C) and CD4⁺ LN cells (D) was then determined based on the gates set on DN thymocytes (B). (E) Using the GFP gates defined in panel B, the expression of CD24, Qa2, αβTCR, CD3, CD28, and IL-7Rα was determined on CD4⁺ RTEs, intermediate, and resident LN cells from neonates and adults. Histograms shown are representative of staining profiles from 6 to 14 individual neonates and 6 to 9 individual adults. For IL-7Rα, data represent 2 independent experiments, using a pool of LN cells from 14 or 15 neonates and 2 adults per experiment.