Fig. 2

Representative H&E stained sections of mouse colon tissue samples from which histological injury score (HIS) was assessed. Micrographs represent samples from each of the treatment groups. Mice in the Control groups were fed an AIN-76A diet, while those in the Inoculation groups were fed AIN-76A diet and received a single oral inoculation of a mixture of Enterococcus faecalis and E. faecium cultures and complex intestinal flora (CIF) derived from FVB/N mice raised under conventional conditions (EF.CIF). In panel a (FVB Control), there is no evidence of inflammation. In panel b (FVB Inoculation), there is evidence of minimal and focal inflammatory cell infiltrates in the mucosa (as indicated by “in”) with an intact epithelial layer. Panels a and b are typical of FVB mice in both the Control and Inoculation groups. In panel c (Mdr1a ^–/– Control), there is severe mucosal, submucosal and transmural inflammation and damage to the tissue architecture, with little or no normal tissue remaining; there are also crypt abscesses (indicated by “ab”), and clusters of infiltrating monocytes (“m”). Panel d (Mdr1a ^–/– Inoculation) shows diffuse inflammatory cell infiltrates in the mucosa and submucosa (as indicated by “in”) with erosions and distorted villous structure; although there are still some crypts (“c”), these are irregular. Panels c and d are typical of Mdr1a ^–/– mice in both the Control and Inoculation groups. All images were captured at 10× magnification