FIG 6.

Stx2a cytotoxicity for Vero cells in the presence of the B subunit of Stx1a or Stx2a toxoid (Stx2*). Vero cells were intoxicated with a set concentration of Stx2a mixed with various concentrations of the Stx1a B subunit (dark blue bars) or Stx2* (light blue bars). Each bar represents the median for three separate experiments, and the error bar indicates 1 standard deviation. Symbols mark concentrations of Stx1B or Stx2* that resulted in an optical density at 590 nm (OD₅₉₀) significantly different from that with Stx2a alone by use of Dunnett’s multiple-comparison test (^, P ≤ 0.01; #, P ≤ 0.001).