Positive correlation between the number of GCs and the efficiency of Lm intestinal invasion and systemic dissemination. IL-33 or PBS alone was administered daily intraperitoneally to iFABP-hEcad transgenic mice for 3 d. Imaging and bacterial inoculation were performed on day 3. (A) Optical section of intestinal villus stained with WGA and for F-actin. Intestinal villi of IL-33–treated mice (bottom) exhibit far more GCs, and GCs secrete far more mucus than PBS-treated control mice (top). (B) Inoculation of intestinal ligated loop were performed on day 3 with 3 × 109 of the indicated strain for 45 min. Panels show optical section of intestinal villus after a ligated loop infection of PBS-treated mouse with Lm WT, IL-33–treated mouse with Lm WT, or IL-33–treated mouse with Lm ΔinlA. Infected intestinal villi were stained for F-actin, nucleus, and Lm (boxes and insets). (A and B) 250-µm vibratome sections are shown. Pictures are representative of two mice. Bars, 10 µm. (C) Quantification of GCs and internalized Lm in intestinal villus of PBS- or IL-33–treated mice after a ligated loop infection of 45 min with 3 × 109 Lm. For each intestinal villus, GCs were enumerated on the larger longitudinal section of observed villi. Error bars indicate SD. n = 20 villi from two mice. (D) Quantification of Lm in the spleen after a ligated loop infection of 45 min in PBS- or IL-33–treated mice on day 3. Horizontal bars indicate the mean. n = 4 mice (**, P < 0.01, as assessed by Student’s t test).
