Tg(Prox1-CreERT2) efficiently targets the entire mesenteric lymphatic vasculature and depletes S1PR1. (A) The proximal and distal mesenteric vasculature of P10 Tg(Prox1-CreERT2);R26^mT/mG (TM@P1–7) pups were analyzed by IHC for PROX1 and autofluorescence of membrane-targeted GFP and membrane-targeted tdTomato. Downregulation of tdTomato and upregulation of GFP confirmed the efficient targeting of proximal and distal mesenteric lymphatic vessels by Tg(Prox1-CreERT2). GFP signal was semiquantitatively measured and plotted. (B) The proximal and distal mesenteric vasculature of P10 S1pr1^f/f (TM@P1–7) and S1pr1^iΔLEC (TM@P1–7) littermates were analyzed using the indicated antibodies. Semiquantitative measurement of the fluorescence signal confirmed that S1PR1 was specifically and efficiently deleted from the lymphatic vessels of S1pr1^iΔLEC pups. Arrows point to blood capillaries in which S1PR1 expression was comparable between the two genotypes. RFA, relative fluorescence activity. Scale bar is 100 μm. Statistics: (A) n = 4. Each dot represents the fluorescent intensity of a single vessel. Three proximal and three distal vessels from each mesentery were measured. (B)n = 4 S1pr1^f/f; n = 3 S1pr1^iΔLEC pups. Each dot represents the RFA of a single vessel. Three proximal and three distal vessels from each mesentery were measured. The graphs were plotted as mean ± SD. Unpaired t test (A) and two-way ANOVA (B) were performed for the statistical analysis. ***P < 0.001; ****P < 0.0001.