Effects of vaccination on differential IL-8 mRNA expression between M. tuberculosis H37Ra- and H37Rv-infected alveolar macrophages. In vitro-cultured alveolar macrophages from nonvaccinated (A) and BCG-vaccinated (B) guinea pigs were infected with live M. tuberculosis H37Ra (open bars), or H37Rv (MOI, 1:1) (hatched bars) for 3, 12, and 24 h. Total RNA from the macrophages was collected, reverse transcribed to cDNA, and detected by real-time PCR by using probes for guinea pig IL-8 and 18s rRNA. Fold induction was determined from Ct values normalized for 18s expression and then normalized to the value derived from nonvaccinated controls. Alveolar macrophages isolated from nonvaccinated guinea pigs infected with H37Ra showed no significant difference in expression of IL-8 RNA when compared to alveolar macrophages infected with H37Rv at any time point (A). H37Ra-infected alveolar macrophages isolated from vaccinated guinea pigs showed significantly more IL-8 RNA expression than did alveolar macrophages infected with H37Rv at 12 and 24 h (B). Data are means ± standard errors of the means of four animals. P values of <0.05 (*) were considered significant.