HtrA impacts colonic pro-inflammatory cytokine expression during C. jejuni infection. Immediately after weaning, infant mice were perorally infected with C. jejuni NCTC11168 (WT, closed circles) or the mutant strain NCTC11168∆htrA (∆htrA, open circles). Uninfected animals (Naïve; open diamonds) served as negative controls. (A) TNF-α protein and (B) IFN-γ mRNA expression levels were determined in ex vivo biopsies taken from colons at day 7 p.i. by ELISA and quantitative real time PCR technique, respectively. Numbers of analyzed animals are given in parentheses. Means (black bars) and levels of significance (P-values) determined by the Mann–Whitney-U test are indicated. Data shown were pooled from at least two independent experiments.