While the SI of the low-affinity CD4-Nb4-Cy5.5 did not exceed the SI of the control Nb at any time (Supplementary Figure 10B), CD4-Nb1-Cy5.5 reached its maximum SI within the HPB-ALL xenograft of ~1.8-fold above the control Nb at 30 min and slowly declined to ~90% and ~80% of maximum after 2 and 4 h, respectively (Figure 5B). This evidence concerns the gene CD4 and acute lymphoblastic leukemia.