Figure 1. Low-dose rapamycin potentiates the inhibitory effects of T_reg on TA development.

(A) Experiment set-up: Side branches of human internal mammary artery were transplanted into immunodeficient BALB/c Rag2^−/−Il2rg^−/− mice. The recipients were injected the following day with 10 × 10⁶ allogeneic human PMBCs administered i.p. Some of the mice additionally received 1 × 10⁶ ex vivo expanded CD127^lo T_reg-injected i.p. at the same time as the PMBCs or 300 μg/kg rapamycin injected i.p. on days 7, 8 and 10 after the transplant. A fourth group of mice received a combination of PBMCs, T_reg and rapamycin. The arterial grafts, blood and spleen were collected 30 days after the surgery. (B) Representative photomicrographs showing development of TA in the PBMC (n = 6); PBMC and rapamycin (n = 6); PBMC and T_reg (n = 4); PBMC and T_reg and rapamycin (n = 5) groups. The grafts have been stained with Elastin/van Gieson. The elastic lamina in the media stain purple and the cellular cytoplasm pink. The newly formed neointima is delineated by the internal elastic lamina (IEL) and the vascular lumen. (C) Quantification of TA expressed as luminal occlusion, percentage of the area inside the IEL occupied by the neointima. The box plots show median, 25th and 75th percentiles as well as the highest and lowest values. *p < 0.05, ***p < 0.001.