Fig. 1: Characterization of endogenous and transplanted thymi.

Fetal thymi were transplanted under kidney capsules of recipient mice and endogenous thymi (ET) and transplanted thymi (TT) were analyzed 4–9 weeks later. a Endothelial cell density in the cortex, the cortico-medullary junction (CMJ), and medulla were assessed in frozen sections of TT (closed bars) and ET (open bars) after staining for CD31 and region-specific markers (Supplementary Fig. 1a); n = 5 experiments. b Relative frequencies of medullary (mTECs; filled bar) and cortical thymic epithelial cells (cTECs; empty bar white) in TT and ET were assessed by flow cytometry. n = 5. c The shortest distance between capsule and medullary border in TT (n = 10) and ET (n = 23; Student’s two-tailed, unpaired t test, P = 0.0001). d Dendritic cell (DC) density in cortex, CMJ and medulla in frozen sections of TT (closed bars) and ET (open bars) after staining for CD11c and region-specific markers (Supplementary Fig. 1b); n = 5 experiments. e DC subset composition in spleen (S), ET, and TT. Data were pooled from two independent experiments with n = 10 mice/each. f–j Recruitment of circulating DCs to spleen (S), TT and ET was compared in competitive homing assays. A 1:1 mixture of differentially labeled treated and control DCs was injected IV into mice that were previously transplanted with a fetal thymus. The homing index (i.e., the ratio of treated:control DC corrected for input ratio) was determined after 18 h by FACS in single-cell suspensions of each recipient tissue. Homing indices were markedly reduced in ET and TT, but not in spleen after f LPS-induced DC maturation, g inhibition of chemokine receptor signaling with pertussis toxin (PTX), or h DC treatment with a blocking anti-α₄ integrin mAb. Results were pooled from two independent experiments, n = 10 mice/group. i and j The role of endothelial adhesion molecules in homing of adoptively transferred DCs was assessed after 18 h by comparing DC accumulation in control mice and animals treated with blocking mAb to VCAM-1 (i) or P-selectin (j). Pooled data from two experiments, n = 5 mice/group. f, g, i ****P < 0.0001, ***: P = 0.0002. h **P = 0.0069, *P = 0.0364. j *P = 0.0369 (ET) and P = 0.022 (TT).