2-DE profile of ECPs and OMPs and immunoblot. 2-DE profile of OMPs (A) and ECPs (B) from A. pleuropneumoniae JL03 strain. Preparative gel stained with Silver Nitrate. Immunoblot of OMPs and ECPs from convalescent sera (C) and (D). The gel spots were encoded using a letter followed by the protein number, which was assigned based on their similar locations on different gels/membranes.