FIGURE 1.

Relationship between gangliosides and release of IL-8 induced by alpha-toxin. A549 cells (1.0 × 10⁷ cells/ml) were treated with various concentrations of PPMP or neuraminidase at 37 °C for 4 days or 60 min, respectively, and then the cells were incubated with 1.0 μg/ml alpha-toxin. A, IL-8 in the culture supernatants 3 h after the addition of the toxin was determined by ELISA. Values represent the mean ± S.E.; n = 3; *, p < 0.01; **, p < 0.005, compared with the release of IL-8 in the cells treated with alpha-toxin. B, the pretreated cells with these inhibitors were incubated with Cy3-alpha-toxin for 15 min. The cells were fixed in 4% paraformaldehyde and analyzed using fluorescence microscopy. The fluorescence intensity in the visual fields was measured as described under “Experimental Procedures.” The binding of alpha-toxin to the intact cells was set as the maximal response (100%) against which all other results were compared. Values represent the mean ± S.E.; n = 3; *, p < 0.01; **, p < 0.005, compared with the binding of alpha-toxin in the untreated cells.