Fig. 4

(A) Intestine section from untreated fish; note the evident reduction in intensity of tlr3 staining with respect to VSL#3-treated fish, characterized by a weak and irregular enterocyte expression, without any staining of cell free pole membranes (bar = 200 µm). (B) Intestine section from treated fish; note the intense and diffuse presence of tlr3 in the mucosal epithelium. The stain is almost exclusively restricted along the superficial margin of enterocytes (arrow heads), and shows a continuous and constant pattern (bar = 200 µm). (C) In section from untreated fish, note the substantial negativity for the presence of Nos2a, both in the epithelium and in endothelial cells (bar = 200 µm). (D) In intestine section from treated fish, an evident presence of Nos2a is observed, especially in endothelial cells (large arrows) or in scattered mononuclear cells (presumably macrophages) interspersed throughout the mucosal chorion (arrow heads). Note the molecule is also localized in some epithelial cells (small arrow); (bar = 200 µm). (E) Untreated zebrafish show low level of immunoreactivity for Tgfb1a both in the epithelium and in mononuclear cells (bar = 200 µm). (F) In VSL#3-treated fish, intestinal presence of Tgfb1a was strong and diffuse throughout the epithelium (large arrows) and in some mononuclear cells (small arrows); (bar = 200 µm). (G) In untreated fish the localization of the p65 subunit of the Nfkb heterodimer is restricted to scattered epithelial cells (bar = 200 µm). (H) Similarly to Tgfb1a localization, the p65 subunit of the Nfkb heterodimer is present in a large proportion of enterocytes (large arrows). Also note the presence of this marker in many mononuclear cells (small arrows), infiltrating the lamina propria of the intestinal mucosa of VSL#3-treated zebrafish (bar = 200 µm).