Role of HtrA in extra-intestinal histopathological sequelae following C. jejuni infection of infant mice. 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. Seven days following C. jejuni infection extra-intestinal immunopathological sequelae were assessed in H&E stained paraffin sections taken from (A) liver, (B) kidneys, and (C) lungs by applying respective standardized histopathological scoring systems. Means (black bars), levels of significance (P-values) determined by the Mann–Whitney-U test and numbers of analyzed animals (in parentheses) are indicated. Data shown were pooled from three independent experiments.