Immunolocalization of CsSERPIN and CsSERPIN3 in metacercariae of C. sinensis. A–C were probed with serum from rats immunized with PBS (negative control); D–F were probed with serum from rats immunized with anti-rCsproSERPIN; G–I were probed with serum from rats immunized with anti- rCsproSERPIN3. B, E, and H are fluorescence microscopy images; A, D, and G are corresponding optical images of B, E, and H. C, F and I are superposed images (C, F, and I) of the previous two. OS, oral sucker; EB, excretory bladder; CW, cyst wall.