FIG. 1.

Comparison of TNF-α mRNA kinetics in THP-1 cells stimulated with Stx1, LPS, or Stx1 plus LPS. Differentiated THP-1 cells (5 × 10⁶ cells/ml) were stimulated with Stx1 (400 ng/ml), LPS (200 ng/ml), or both for 0 to 72 h. Total RNA (10 to 15 μg) was subjected to Northern blot analysis using ³²P-labeled TNF-α and GAPDH cDNA probes. Hybridization was detected and quantitated using a PhosphorImager and expressed as percentage mRNA above basal (unstimulated) expression. (a) Representative Northern blots of Stx1-, LPS-, and Stx1-plus-LPS-induced TNF-α mRNA. (b) Mean intensities of percentage mRNA above basal expression for each time point ± standard errors of the means (error bars) from three independent experiments. Values that are significantly different (P < 0.05) are indicated as follows: *, a significant difference between the values for cells treated with LPS alone and Stx1 plus LPS; #, a significant difference between the values for cells treated with Stx1 alone and Stx1 plus LPS.