Kinetics of αIIbβ3 biogenesis in cells derived from umbilical cord blood (CB) cells. (A) Pulse-chase analysis of CB cells with the αIIbβ3 complex-specific mAb 10E5 showed a pattern of pro-αIIb, mature αIIb, and β3 kinetics similar to those in stably transfected HEK293 cells (compare with Figure 2). Similar to the results in stably transfected HEK293 cells, the anti-αIIb mAb CA3 and the anti-β3 mAb 7H2 revealed the presence of pools of free pro-αIIb and β3, respectively, in the CB cells at a time when αIIbβ3 production was essentially complete. (B) The anti–β3 LIBS mAbs AP5 and LIBS2 recognized pro-αIIbβ3 but not mature αIIbβ3, and the anti–αIIb LIBS mAb PMI-1 precipitated only a small subpopulation of pro-αIIb. Each box represents a separate experiment.