Detection of the E2A/pbx1 chimeric protein in patient bone marrow specimens using the G289-781 MoAb. (A) Western blot analysis of specimens from four representative patients (lanes 1 to 4), 697 cell lysate (lane 5), and Namalwa cell lysate (lane 6) using the G289-781 MoAb. (B) Flow cytometric analyses of the same patient specimens with an isotype control antibody (- - - -) or G289-781 MoAb (——). (C) Representative immunohistochemical staining of bone marrow specimens from patient 1 (top) and patient 3 (bottom) using an isotype-matched negative control antibody (left), an E2A-specific positive control antibody (G98-271.1, center), and the E2A/pbx1-specific G289-781 MoAb (right).