Identification of myoferlin as a uniquely recognized self-antigen. (A) Silver stain of a 3%-8% Tris-acetate gel of proteins immunoprecipitated (IP) from HEp-2 cell lysate by the indicated recombinant tumor Igs. (−) indicates lanes containing tumor Ig proteins only; IP, lanes containing the immunoprecipitated proteins; Ly, lysate; and B, lysate IP with protein G beads only. The left arrow indicates the 236-kDa protein immunoprecipitated by the tumor Ig of patient 1152; the right arrow points to the location of the tumor Igs. (B) Immunoblotting for myoferlin in immunoprecipitation samples from HEp-2 cell lysate. (C) Immunoblotting for myoferlin in immunoprecipitation samples from 293T cells transfected with recombinant myoferlin. (D) A total of 98 tumor Igs were tested for binding to recombinant myoferlin by ELISA. Myoferlin-HA was immobilized using anti-HA antibodies on lysates from untransfected (left panel) and transfected 293T cells (right panel). Shown is a representative graph of OD_405-490 values for 14 different nonbinding patients' tumor Igs (solid lines) compared with tumor Ig for patient 1152 (dotted line). The ability of tumor Ig 1152 to bind myoferlin was confirmed in at least 2 independent experiments.