E. coli Facilitates Murine Campylobacter Infection Figure 8. Immune responses following C. jejuni infection of adult mice with increased E. coli loads. In conventionally colonized 3-months- old adult mice intestinal E. coli loads were raised up to 108 bacteria per gram feces by adding live E. coli into the drinking water (+ E. coli) as described in Methods. Then, mice were orally infected with C. jejuni strain ATCC 43431 (crossed circles) or B2 (solid circles). The average numbers of apoptotic cells (positive for caspase-3, panel A), neutrophilic granulocytes (Neutrophils, positive for MPO-7, panel B), macrophages (positive for F4/80, panel C), T-lymphocytes (positive for CD3, panel D), regulatory T-cells (Tregs, positive for FOXP3, panel E) and B-lymphocytes (positive for B220, panel F) from at least six high power fields (HPF, 4006magnification) per animal were determined microscopically in immunohistochemically stained colon sections at day 12 p.i. Uninfected mice (Na¨ıve, open circles) served as negative controls. Numbers of analyzed animals are given in parentheses. Means (black bars) and levels of significance (P-values) as compared to uninfected (Na¨ıve) control mice (determined by the Student’s t-test) are indicated. Data shown are pooled from at least three independent experiments. doi:10.1371/journal.pone.0035988.g008 PLoS ONE | www.plosone.org 10 May 2012 | Volume 7 | Issue 5 | e35988