Fig. 2: Intestinal conditioning of GF mice with STm^Aux induces B cell dependent functional intestinal immunity.

a Germ-free mice were enterally conditioned with six doses of 10¹⁰ CFU of STm^Aux (red triangles, n = 5 animals) or were left untreated (gray-filled circles, n = 5 animals). Four weeks after the first treatment (day 0) mice were challenged with wild-type STm (10⁵ CFU) and analyzed 2 days later. Each symbol represents one individual. b Shedding of wild-type STm in feces 1 day after challenge. c Cecal histopathology score at day 2 after challenge. Each symbol represents one individual. d Lipocalin-2 concentration in cecal contents at day 2 after challenge. e Bacterial burden of wild-type STm in mLNs, spleens, and livers at day 2 after challenge. f Intestinal secretory IgA was isolated at day 2 after challenge. IgA binding to wild-type Salmonella was quantified at different antibody concentrations by live bacterial flow cytometry. Connected symbols represent one individual. g STm-specific titer (−logEC₅₀) calculated from the STm-IgA titration curve plotted in Fig. S4J. h Experimental design: Germ-free Jh^−/− (open symbols, n = 5 animals) and wild-type control mice (filled symbols, n = 4 animals) were enterally conditioned three times with 10¹⁰ CFU of live STm^Aux. Thirty-three days after the first treatment (day 0) all mice were challenged with of wild-type STm (10³ CFU). i Bacterial burden of wild-type STm in mLNs, spleens, and livers at day 3 after challenge. j Lipocalin-2 concentration in cecal contents at day 3 after challenge. Statistics: bars indicate mean (b, d, e, g, i, j) or median (c) values. Horizontal dotted lines indicate the detection limit. Panel c was analyzed with a two-sided Mann–Whitney U-test. Panels d, e, g, i and j were analyzed with the unpaired two-tailed t-test. Source data are provided as a Source Data file. Detailed statistical metrics are available in the Supplementary Statistical Analysis file.