2.3 Haematoxylin-eosin (HE) staining
At necropsy, colonic tissues were collected, immersed in 4%
paraformaldehyde (Solarbio, P110, USA), and stored for 48 h at 4 °C.
Then, 5 μm sections were cut on a Leica RM2016 Microtome (Leica
Biosystem) and stained with haematoxylin and eosin (H&E). The colon and
spleen tissues were fixed at 40 g/L in polyformaldehyde for 12 h. After
dehydration, the tissue was turned transparent with xylene and washed
with PBS. The sample was embedded in paraffin, and the tissue slice was
stained. Colon lesions and inflammatory infiltration of spleen tissue
were observed under an optical microscope. Histological scoring was
based on two parameters as indicated in Table 1 [9]. The total colon
pathology score equalled the inflammatory cell score plus the tissue
damage score.