Stimulation of rat PBMCs with TB antigens. (A) PBMCs from infected rats (3 rats) are stimulated in vitro for 24 h with ESAT-6, CFP-10, or PPD at 10 μg/ml. IFN-γ ELISpot assay was performed at 1 month postinfection with 500 CFU (white bars) or 103 CFU (black bars) of the H37Rv M. tuberculosis strain. (B) The bacterial burden (CFU) was enumerated at 1 month postinfection. Three rats per group were used, and mean numbers of SFCs/106 PBMCs or CFU/lungs ± SDs are shown *, P < 0.05 (Student's t test), comparison between unstimulated and stimulated cells. The experiment was carried out twice. CT, control (unstimulated) group.