Female Balb/c mice (6–8 weeks of age) in the C. sinensis group were intragastrically infected with metacercariae (30 metacercariae per mouse). We determined the success of infection by stool examination. Five mice from each group were randomly selected and were sacrificed at 7, 30, 60, 90, 120 and 180 days postinfection (uninfected mice in same terms were used as controls). The liver tissues were extracted, and tissue sections were prepared. These samples were fixed and cut by a microtome of 4 μm sections. The sections were incubated with mouse anti-CsGRN serum or mouse naïve serum (1:50 dilutions) overnight at 4 °C after being dewaxed in xylene, dehydrated in ethanol, and blocked with normal goat serum. The sections were washed with PBST (0.1% Tween-20 in PBS) and were incubated with horseradish peroxidase-conjugated goat anti-mouse IgG (1:400 dilutions; Proteintech Group) for 1 h. The sections were rinsed with PBS for 15 min, after which the slides were developed with diaminobenzidine (DAB). Next, the sections were counterstained with Mayer’s haematoxylin, dehydrated, cleared in xylene and mounted in PermountH. Images were captured with a microscope (Olympus BX51, Hatagaya, Japan).