Figure 3: Histology of the piglet intestine infected with C. jejuni.

Tissues were obtained on day 4 (a–f) or 5 (i,j) p.i. with C. jejuni 81–176 (b–f,i,j) or from uninfected gnotobiotic control piglets (a,g,h) and analysed using haematoxylin-eosin staining (a–f) or immuno-labelling of (red chromogen) of C. jejuni with a haematoxylin counterstain (g–j). (a) Uninfected ileum; long villi extend deep into the lumen, which is populated by cells with vacuolation of cytoplasmic contents (black arrows), the low cellularity of the lamina propria (blue arrows) and the presence of discrete Payer’s patches (yellow arrows). (b) Infected ileum; villi are shorter and blunter (black arrows) than in uninfected controls, the lamina propria is highly cellular (blue arrow) due to lymphocyte infiltration but also smaller numbers of eosinophils and occasional neutrophils and the sub-mucosal lymphoid tissue (Peyer’s patches) are greatly expanded and coalescing (yellow arrow). (c) Higher magnification of panel b. Larger numbers of mucous cells within the epithelium of the villi (black arrows), large numbers of lymphocytes in the sub-mucosa (blue arrow) and cells undergoing mitosis within the epithelium in the depths of the crypts (yellow arrows). (d) Infected caecum; crypt abscesses (black arrow) and oedematous lamina propria (blue arrow). (e) Infected colon; oedema within the lamina propria and sub-mucosal tissue (blue arrows) and a mild lymphocyte infiltration (black arrows). (f) Infected colon; bacteria in the lumen of the base of an intestinal crypt (black arrow). (g) Uninfected ileum; some non-specific staining of ileal contents, however no bacterial staining was detected and the pattern of staining was different from the infected animals. (h) Uninfected colon. (i) Infected ileum; C. jejuni microcolonies on epithelial cell microvilli (black arrows), C. jejuni in the cytoplasm of epithelial cells (blue arrows), along the basement membrane of the epithelium (yellow arrows) and within the lamina propria (green arrows). (j) Infected colon; C. jejuni was primarily found in crypt epithelial cells (black arrows). Scale bars represent 1,000 μm (a,b), 100 μm (c,d,g), 200 μm (e,h,j), 20 μm (f) and 50 μm (i).