Th cell subsets in neonatal tissues. In the top panels (A-D), RORγt⁺ (blue) and CD45RO⁺ (red) double-positive cells were detected in large numbers in the gut epithelium (A) and gut lymphoid aggregates (B). RORγt⁺CD45RO⁺ cells were virtually absent in lymph nodes (C) and undetectable in the spleen (D). In gut epithelium (E), T-bet⁺CD45RO⁺ cells made up approximately 35% of the CD45RO⁺ cells and these cells were also present to a lesser extent in the gut lymphoid aggregates (F) and nearly absent in the lymph nodes (G). In the spleen (H), T-bet⁺CD45RO⁺ cells represented the largest CD45RO⁺ T-cell subset. These panels are representative of patients 1-10 included in our study. Scale bar indicates 0.1 mm.