Leukocyte counting and flow cytometry. Leukocyte counts (A) were performed in peripheral blood of infected and noninfected myelin oligodendrocyte glycoprotein (MOG)-immunized animals. The leukocyte count was found to be significantly higher in the infected group. Data are represented as means ± SEM of all animals from each group (n = 12, infected; n = 11, noninfected). Flow cytometry was performed in peripheral blood to assess B- and T-cell populations in animals infected with S. aureus and noninfected control group on day 4 postimmunization (pi) (prior to infection) and on day 6 pi (corresponding to day 2 postinfection). B- (B) and T-cell (C) populations were substantially increased in infected animals 2 days after infection. Data are presented as means ± SEM. (n = 4 in each group; *P <0.05; **P <0.01; ***P <0.001).