Here we investigated the role of C. jejuni HtrA in (i) colonization capacity, (ii) translocation, (iii) clinical outcome, (iv) intestinal inflammation, and (v) extra-intestinal sequelae including systemic immune responses following infection of gnotobiotic IL-10−/− mice with the C. jejuni WT strain NCTC11168 and the isogenic knockout mutant strain NCTC11168ΔhtrA. The gene discussed is HTRA1; the disease is infection.