HSCs migration after administration of FK506. (a) Immunostaining with anti-CD31 antibody. Arrows indicate the left and right sides of the dorsal arteries. (b) Immunostaining with anti-CD34 or anti-CD117 (c-kit). Saline-treated fetuses exhibited positive staining for both CD34 and c-kit in the left dorsal artery. FK506-treated fetuses had positive staining on the right-hand side, opposite to that seen in saline-treated fetuses.