Adult mLNSCs derive from FAP⁺ pre-mLTo cells. (A) tdTomato expression in e15.5 and e16.6 FC^Tomato iLN anlagen. Scale bars, 100 µm. Dotted line shows the anlage. (B–F) FAP⁺ cells in e15.5 iLN anlage were analyzed for mLTo cell markers: ICAM and VCAM (B), LTβR (C), MAdCAM-1 (D), Prox-1 (E), and CXCL13 or CCL19 (F). Scale bars, 100 µm (B–E) or 50 µm (F). White boxes indicate enlarged areas. Arrows in F indicate CXCL13⁺FAP⁺ mLTo cells. Images represent three to six embryos from two to three litters.