Effect of scFv/uPA-T on circulating RBCs and its organ distribution in vivo. (A) Distribution of radioactivity in mice after administration of ⁵¹Cr-labeled mouse RBCs followed by the intravenous injection of 4mg/kg scFv/uPA-T or PBS. The animals were killed 1 hour (supplemental Figure 3) or 6 hours (panel A) later and ⁵¹Cr was measured in the blood and major peripheral organs (n = 4). The inset indicates ⁵¹Cr distribution between blood plasma and cells at the indicated times. (B) Distribution of ¹²⁵I-labeled scFv/uPA-T in organs at the indicated times after intravenous injection in mice. Inset: Distribution of ¹²⁵I-scFv/uPA-T between blood plasma and cells (n = 5).