Dose response of purified human antiplatelet GPIIb and GPIIIa monoclonal autoantibodies, 2E7 and 5E5, to the growth of CD41⁺PI⁺ cells in the liquid culture of umbilical cord blood MNCs. Cells were cultured for 8 days in the presence of rhTPO, 10% control plasma, and various concentrations of 2E7 and 5E5. The yields of CD41⁺PI⁺cells in cultures were determined by the 2-color flow cytometric technique (means ± SDs; n was at least 2 for each dose).