Competition between several anti-GPIb mAbs for binding to GPIb on human fixed platelets.

Human platelets were incubated with biotinylated mAbs (bmAb) at a concentration resulting in 50% saturation and with 50μg/mL of unlabeled antibody. Bound bmAb was detected by using HRP-labeled streptavidin. Data given are the percentage binding relative to the binding in the absence of mAb. (A) Novel panel of 5 anti-GPIb mAbs versus each other. Two groups of intercompeting mAbs 27A10, 12G1, 12E4 (group 1) and mAbs 6B4 and 24G10 (group 2) were found. (B) This panel of mAbs versus other anti-GPIb mAbs characterized elsewhere. mAbs 27A10, 12G1, and 12E4 did not compete with any of other mAbs, but mAbs 6B4 and 24G10 competed with mAbs LJ-Ib1, AK2, HIP1, and TM60. The binding of TM60 could be equally blocked by mAbs LJ-Ib1, AK2, HIP1, and TM60. Detection was accomplished using HRP-labeled streptavidin. Data given are the percentage binding (relative to control in the absence of mAb).