Immunoprecipitation of A3-C1 polypeptide by MoAb and hemophilic inhibitor IgGs. Cell culture medium containing³⁵S-methionine–labeled rA3-C1 was incubated with increasing concentrations of IgG from human inhibitors RI or MU and from MoAb CLB-CAg A. Immunoprecipitated ³⁵S-A3-C1 was analyzed as in Fig 1. (A) RI, lanes 1 through 6: 20, 10, 5, 2.5, 1.25, and 0.625 μg/mL; lane 7: no antibody; lane 8: 3 μg/mL of CLB-CAg A IgG. (B) MoAb CLB-CAg A, lanes 1 through 7: 2, 1, 0.5, 0.25, 0.12, 0.06, and 0.03 μg/mL; lane 8: no antibody. (C) MU, lanes 1 through 8: 20, 10, 5, 2.5, 1.25, 0.62, 0.31, and 0.15 μg/mL; lane 9: no antibody; lane 10: 3 μg/mL of CLB-CAg A IgG.