FIG. 1.

(A) Effect of Msp on neutrophil chemotaxis, assayed using the Boyden chamber with 1 μM fMLP as the chemoattractant. Data are expressed as mean percentages of the control level (taken as 100%) ± standard errors (n = 3). *, P < 0.05. (B) The highest concentration of Msp (64.0 μg/ml) was pretreated with preimmune serum, anti-Msp antiserum, or heat at 60°C for 30 min, and the effect on chemotaxis was compared with that of Msp and Msp-free vehicle (control). Data are expressed as mean percentages of the control level (taken as 100%) ± standard errors (n = 3). *, P < 0.05. Note that the antiserum and 60°C samples were not significantly different from control activated samples but were statistically different from Msp-treated samples. This confirms that the observed effect is a result of the Msp and not a contaminating factor in the bacterial preparation.