Characterization of Ccl19-iEYFP ⁺ progenitors in lymph node anlagen and cell fate analysis in peripheral and mesenteric lymph nodes. (A) Schematic representation for the analysis of inguinal and mesenteric lymph node anlagen from Ccl19-iEYFP embryos at the indicated time points. (B–D) Whole-mount confocal microscopy analysis of mesenteric lymph node anlagen from Ccl19-iEYFP⁺ embryos at E15 (B), E16 (C), and E18 (D). Boxed areas indicate regions of higher magnification. Arrows and arrowheads indicate the localization of Ccl19-tTA⁺ cells. High-resolution images are representative for three inguinal and three mesenteric lymph node anlagen from three independent experiments. Scale bars: 80 and 40 µm (B), 150 µm (C, upper panels) and 15 µm (C, lower panels), and 200 µm (D, upper panels) and 15 µm (D, lower panels). (E) Schematic of cell fate analysis of inguinal and mesenteric lymph nodes from Ccl19-iEYFP⁺ mice. (F and G) Fate-mapping analysis of EYFP⁺ cells in inguinal (F) and mesenteric (G) lymph nodes harvested from adult Ccl19-iEYFP⁺ mice after Dox administration starting at E18. Microscopy images are representative for three inguinal and three mesenteric lymph nodes from three independent experiments. Scale bars: 200 µm (F) and 1,000 µm (G). (H) Localization and appearance of FRC subsets and VSMCs in cross sections of mesenteric lymph nodes. High-resolution microscopy images are representative for three mesenteric lymph nodes from three independent experiments. Scale bar: 20 µm (H). Figure was complemented with elements from https://BioRender.com.