Inflamed co-culture set-up: (A) Step 1, (B) Step 2, (C) Step 3, (D) Step 4 of the inflamed co-culture development: In Step 1 (A), the set-up of the stable co-culture was not altered apart from the addition of LPS to the BL compartment at the start of the co-culture with 24 h PMA-differentiated THP-1 cells. In a second step (B), the Caco-2 barrier was primed with IFN-γ before the start of the co-culture. In Step 3 (C), the THP-1 cells were pre-exposed to LPS 4 h before the initiation of the co-culture and, eventually, pre-treated with LPS and IFN-y to stimulate an uninhibited cytokine response in the cells (Step 4; D). [Changes to the previous set-up are marked by red circles.] (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)