Fig. 5.

Stx2 does not bind to normal human colonocytes and its uptake is stimulated by EHEC infection in T84 cells. A and B: representative projection through 5 confocal optical sections (step 0.5 μm) of normal human colonic tissue immunostained with Stx2-Alexa 568 (red) (A) and colabeled with CTB-Alexa 488 (green) (B); nuclei, blue by Hoechst. No Stx2 binding was detected in human colonocytes, but Stx2 (red) labeled some cells in lamina propria which its nature has to be identified. In contract, cholera toxin B (CTB) (green) binds to the human surface and crypt colonocytes. C: representative immunoblot of Stx2-Alexa 790 and GAPDH from infected (10⁴ EDL933/ml) and uninfected T84 cells and exposed apically to different Stx2 concentrations for 4 h. D: corresponding quantification of Stx2 uptake by uninfected (control, open circles) T84 cells or infected for 4 h with 10⁴ EDL933/ml (black squares); *Significant compared with corresponding control conditions, P < 0.01; n = 3 per each condition.