Recognition of M. hyopneumoniae P97 and A. pleuropneumoniae ApxIII by serum isolated from pigs immunized with the Ap97 vaccine. A. Western blot analysis of the cell membrane fraction of M. hyopneumoniae (Lane 1) as well as TCA-precipitated proteins from the culture media (Lane 2) and cell lysate (Lane 3) of A. pleuropneumoniae was performed with Ap97-vaccinated pig serum. B. Western blot analysis of the protein samples described in panel A was performed with PBS-vaccinated pig serum. Arrows indicate target band sizes.