Impaired LN development in Clec1b^−/− embryos. (A) Macroscopic observation of newborns Clec1b^−/−, Clec1b^+/−, and Clec1b^+/+ littermates revealed the absence of inguinal and mesenteric LNs in Clec1b^−/−. Fraction of the number of newborn mice with detectable LNs/number of mice sacrificed. (B) Flow cytometric analysis of mesenteric LN single-cell suspensions from Clec1b^−/− and Clec1b^+/+ littermates newborn and E16.5 stained with CD45, CD4, ICAM-1, and VCAM-1. Percentage of CD45⁺ hematopoietic cells is shown in the histogram (first column); percentages of CD45⁺CD4⁺ LTi cells (second column), and of ICAM-1^highVAM-1^high LTo cells, in the CD45⁻ stromal fraction (third column) are shown in the dot plots. (C) Quantification of the recruitment of LTi cells (gated as shown in B second column) and of LTo cells in the CD45⁺ stromal fraction (gated as shown in B third column) in the LN anlage at E16.5, E18.5, and newborn stages. Data are representative of 3 to 5 embryos for each time point and phenotype across at least 2 independent experiments. Unpaired Student t test, *P < .05.