Colonization and pathology of <i>Sigirr^−/−</i> and TLR-deficient mice by <i>C. jejuni ΔkpsM in vivo</i>.

<p>(A) H&E stained histological sections of ceca recovered from <i>Sigirr^−/−</i>, <i>Tlr2^−/−/Sigirr^−/−</i> and <i>Tlr4^−/−/Sigirr^−/−</i> mice, colonized with <i>C. jejuni ΔkpsM</i> 7 DPI, at 100× magnification. Very severe inflammation is evident in the <i>Sigirr^−/−</i> and <i>Tlr2^−/−/Sigirr^−/−</i> mice, however once again, no significant pathology was evident in the <i>Tlr4^−/−/Sigirr^−/−</i> mice. (B) Immunofluorescence of <i>Sigirr^−/−</i> mice infected by <i>C. jejuni ΔkpsM</i>, 7 DPI. Sections are stained for DAPI (blue), β-actin (green), and <i>C. jejuni</i> (red). <i>Sigirr^−/−</i> mice exhibit significant neutrophil infiltration, hyperplasia, and <i>C. jejuni ΔkpsM</i> is clearly visible in large masses within the cecal crypts. (C) Pathological scoring was done by two blinded observers, using H&E stained, formalin-fixed cecal tissue sections. Each condition represents a minimum of three separate experimental replicates, with 2–3 mice per experiment. Control mice were used as a reference and consisted of 3 uninfected mice, pre-treated with a single dose of 5 mg/100 µl vancomycin, and euthanized 3 days post-treatment. Only <i>Sigirr^−/−</i> and <i>Tlr2^−/−/Sigirr^−/−</i> mice at 7 DPI showed a significant increase in pathology (****p<0.0001), relative to the uninfected <i>Sigirr^−/−</i> control. The <i>Tlr2^−/−/Sigirr^−/−</i> mice also exhibited statistically significantly higher inflammation at 7 DPI relative to <i>Sigirr^−/−</i> mice also at 7 DPI (**p<0.001). In contrast, none of the mouse strains at 3 DPI showed any statistically significant increase in pathology, relative to control mice. Statistical significance was determined using a two-way ANOVA and a Bonferroni post-test.