FIG. 3.

IL-8 and MCP-1 production by R. rickettsii-infected ECs of different origin. Culture supernatants from cells infected with R. rickettsii for 3, 7, 14, and 21 h and corresponding uninfected controls were collected and assessed for IL-8 and MCP-1 levels by ELISA. At least two dilutions of each sample were assayed in duplicate, and OD values corresponding to the linear range of the standard curve were used for the determination of chemokine concentrations. Results are expressed as mean fold induction of IL-8 (A) and MCP-1 (B) over the basal levels of secretion by uninfected cells (Control), which were assigned a value of 1 for the ease of comparison. The data sets are presented as the mean ± standard error (SE) of at least three independent experiments (n ≥ 3). Statistically significant differences in comparison to the basal IL-8/MCP-1 secretion by uninfected cells are indicated by the asterisks.