Cytokine mRNA expression of splenic granulomas from guinea pigs aerosol-challenged with M. tuberculosis. Expression of IFN-γ, TGF-β, TNF-α, IL-12p40, and iNOS mRNA were measured from granulomas microdissected from the spleen of nonvaccinated (open bars) and BCG-vaccinated (shaded bars) guinea pigs 6 weeks after virulent challenge (A). Values for Ct were converted to “expression levels” to allow for fold comparisons between samples, expression level = 2(40-Ct). Data were normalized to HPRT rRNA followed by values derived from nongranulomatous tissues and expressed as means ± SEM (n = 8–10 capfuls of microdissected tissue from the spleen). Comprehensive charts mapping the relative contributions of cytokine mRNA expression to granulomas from the spleens of (B) nonvaccinated and (C) BCG-vaccinated guinea pigs. The sum of the relative expression levels of IL-12p40 mRNA (green), TNF-α mRNA (yellow), TGF-β mRNA (blue), IFN-γ mRNA (red), and iNOS mRNA (gray) in the splenic granulomas microdissected from nonvaccinated and BCG-vaccinated guinea pigs was used to calculate the relative proportion of transcripts represented by each cytokine.