FIG 1.

2D6 IgA reduces V. cholerae attachment to epithelial surfaces in vivo. V. cholerae O395 was either untreated (A) or treated with 2D6 IgA (B) or 2D6 Fab fragments (C) and injected into 1-cm ligated ileal loops of BALB/c mice, as described in Materials and Methods. After 30 min, the loops were excised, frozen, cryosectioned, and stained with fluorescently labeled V. cholerae antiserum (red) or CD11c (blue) to detect mucosal dendritic cells (DCs). Stained cryosections were then visualized by confocal microscopy. In each case, the panels in the right-hand column are zoomed-in images of the panels in the left-hand columns. In panels A, V. cholerae was observed in close association with the epithelium (arrows) and penetrating the intestinal crypts (arrowheads). In panels B, 2D6 IgA-treated bacteria were largely aggregated in the lumen (arrows) and rarely in the crypts (arrowheads). In panels C, 2D6 Fab fragment-treated V. cholerae cells were observed in close association with villus epithelium and in the crypts (arrowhead). Scale bars, left column, 300 μm; right column, 50 μm. Abbreviations: PP, Peyer's patches; V, villi; L, lumen.