Fig. 6.

Depletion of cholesterol reduces CDT holotoxin binding to cells. CHO-K1 cells were left untreated (upper) or treated with 10 mM MβCD (lower) for 1 h at 37°C prior to incubation with CDT holotoxin (200 nM). After incubation for 2 h at 4°C, the cells were probed with control preimmune serum or individual antiserum against each CDT subunit and stained with FITC-conjugated anti-mouse IgG. The level of binding activity was analyzed by flow cytometry for FITC fluorescence. The results represent the means and standard deviations from three independent experiments. The lower right panel shows the quantitative data of the CDT binding activity. An asterisk indicates significance compared to results for each untreated MβCD group, as determined by Student's t test (P < 0.05).