Cell fate analysis of Ccl19-tTA ⁺ progenitors in peripheral and mesenteric lymph nodes. (A–C) Whole-mount confocal microscopy images showing inguinal lymph node anlagen from Ccl19-iEYFP⁺ embryos at E15 (A), E16 (B), and E18 (C). Boxed areas indicate regions of higher magnification. Arrowheads indicate appearance of Ccl19-tTA⁺ LTo cells around the blood vessel. High-resolution microscopy images are representative for three inguinal lymph node anlagen from three independent experiments. Scale bars: 40 µm (A); 40 and 15 µm (B and C, left and right panels). (D and E) Fate-mapping analysis of EYFP⁺ cells in inguinal and mesenteric lymph nodes harvested from adult Ccl19-iEYFP⁺ mice after Dox administration starting at E16. Microscopy images are stitched tile scans and representative for three inguinal and three mesenteric lymph nodes from three independent experiments. Scale bars: 200 µm (D) and 800 µm (E). (F) Quantitative analysis of the Ccl19-iEYFP transgene activity along the mesenteric lymph node chain of fate-mapped mice (E18 to adult). Data are shown as mean intensity values of n = 5 mice from three independent experiments. Adjusted P value was calculated using the Kruskal–Wallis test for Dunn’s multiple comparisons. (G and H) Confocal microscopy images showing localization of EYFP⁺ cells in the T cell zone and medulla in cross sections of inguinal (G) or mesenteric (H) lymph nodes after fate-mapping from E16. High-resolution microscopy images are representative for three inguinal and three mesenteric lymph nodes from three independent experiments. Scale bars: 15 µm. (I) Localization and appearance of FRC subsets and VSMCs in cross sections of inguinal lymph nodes from adult Ccl19-iEYFP⁺ mice after Dox administration starting at E18. High-resolution microscopy images are representative for three inguinal lymph nodes from three independent experiments. Scale bars: 20 µm. (J) Flow cytometric analysis of VSMCs in mesenteric lymph nodes from adult Ccl19-iEYFP⁺ mice after Dox administration starting at E18 (n = 3). sMLN, small intestinal mesenteric lymph node; cMLN, colonic mesenteric lymph node.