FIG 5.

Toxin-induced changes in chemokine and cytokine mRNA levels in U937 cells. U937 cells were treated with 1 μg/ml SubAB, SubA_A272B, or Stx2 or were left untreated (control) for 4 or 24 h. Total RNA was then extracted from the cells, and chemokine/cytokine mRNAs (as indicated) were quantitated by real-time RT-PCR (see Materials and Methods). The results are expressed as fold increases in concentrations of mRNAs relative to levels in control cells. The data are means and SEM from at least 8 samples from three independent experiments. ***, P < 0.001 relative to control cells (Student's unpaired, two-tailed t test).