Immunoprecipitation of the 97A6 reactive antigen. 10⁷ KU-812 cells were surface-iodinated with¹²⁵I-iodine by the lactoperoxidase method and immunoprecipitated under reduced and nonreduced conditions with 97A6 antibody-coated beads or control beads, respectively. The precipitates were then separated by 5% to 15% SDS-PAGE and visualized by radiographic photography. “R” indicates reduced conditions; “NR” indicates nonreduced conditions. Molecular weight standards are indicated on the left.