Fig. 4.

S-layer protein-coated- or uncoated-cell wall fragments protect against F4⁺ETEC-induced increase in membrane permeability differently. Caco-2/TC7 cells were untreated (control, C), infected with F4⁺ETEC (E), treated with S-layer protein-coated (S-CWF) or uncoated-cell wall fragments (U-CWF), co-treated with S-CWF or U-CWF and E (S-CWF + E or U-CWF + E, respectively), pre-treated with S-CWF or U-CWF before F4⁺ETEC infection (prS-CWF + E or prU-CWF + E, respectively). Phenol red was added in the apical (AP) compartment, for 1 h, and then determined spectrophotometrically in the basolateral (BL) compartment. The results are expressed as apparent permeability (P app). Values represent means ± SD of at least three independent experiments, carried out in triplicate. Statistically significant differences are shown and * indicates P < 0.001 from the control group, ^# indicates P < 0.001 from the ETEC group