FIG. 4.

Accumulation of peroxide in EA.hy 926 human endothelial cells infected with different isolates of R. rickettsii. Squares, uninfected cells; solid circles, cells infected with 1 PFU/cell; open circles, cells inoculated with 0.25 PFU/cell. The data are presented as means ± standard errors (for three dishes per experimental variable). Some error bars are not visible due to the low standard error of the mean obtained. The statistical significance of the variables compared is given in the text.