FIG 3.

B. longum srp mediates the protective effect observed in mice. NOD/DQ8 mice were sensitized with cholera toxin and pepsin-trypsin-digested gliadin 1× per week for 3 weeks. Nonsensitized mice (controls) received cholera toxin alone. Subsequently, sensitized mice were treated daily with B. longum srp⁺ (srp⁺), B. longum Δsrp (Δsrp), or B. longum srp(Con) and simultaneously challenged with gliadin 3× per week for 2 weeks. Control mice received PBS–20% glycerol. (A) CD3⁺ intraepithelial lymphocytes in small-intestinal villus tips were quantified and expressed as IELs per 100 enterocytes. Mice treated with srp-expressing B. longum srp⁺ or B. longum srp(Con) had significantly lower numbers of IELs than B. longum Δsrp-treated mice. Representative images were captured at ×40 magnification (n = 10 to 11/group). (B) Small-intestinal sections were subjected to H&E staining, and villus (V) and crypt (C) lengths were measured via light microscopy, expressed as V:C ratios. B. longum srp(Con) treatment in gliadin-sensitized mice resulted in significantly higher V:C ratios than B. longum Δsrp treatment. Representative images were captured at ×10 magnification (n = 10 to 11/group). (C) Paracellular permeability was restored in sensitized NOD/DQ8 mice treated with B. longum strains expressing srp, i.e., B. longum srp⁺ and B. longum srp(Con). Proximal small-intestinal sections were mounted on Ussing chambers to measure ex vivo paracellular permeability, expressed as ⁵¹Cr-EDTA flux (n = 7 to 8/group). (“Hot sample” refers to the collection of mucosal buffer after addition of ⁵¹Cr-EDTA [100%]. All serosal samples collected afterwards are compared to the hot sample.) Data are shown as means ± SEM. Control, nonsensitized, no treatment; srp⁺, B. longum srp⁺; Δsrp, B. longum Δsrp; srp(Con), B. longum srp(Con). Statistical significance determinations were performed by ANOVA followed by Bonferroni post hoc analysis. ***, P < 0.001; *, P < 0.05.