The present invention relates to novel methods of identifying and producing an anti-platelet autoantibody. More preferably, the invention relates to identification and production of a human monoclonal anti-platelet autoantibody. Moreover, the invention relates to methods for treating or alleviating a disease, disorder or condition mediated by an anti-platelet autoantibody specifically binding with a platelet, or a component thereof, such as, but not limited to, idiopathic thrombocytopenic purpura, among others. Preferably, the antibody is an unglycosylated H44L4 Fab.