FIG. 3.
Recombinant LLO induces IL-6 production only at a sublytic dose. (A) Cytolytic effect of rLLO on Caco-2 cells. Caco-2 cells were stimulated with different doses of rLLO and rLLOW492A for 3 h, and the LDH activity in culture supernatants was assessed. The results are representative of the results of three similar experiments. The data are the means ± standard deviations for three determinations. (B) Viability of Caco-2 cells after stimulation with rLLO. Caco-2 cells were treated with PBS (P) or 1% Triton X-100 (T) or were stimulated with different doses of rLLO or rLLOW492A for 3 h. Then the WST-1 reagent was added to the cultures, the cells were incubated for 30 min, and the absorbance at 450 nm of culture supernatants was measured. The results are representative of the results of two similar experiments. The data are the means ± standard deviations for three determinations.