FIG. 1.

Comparison of skin test responses and in vitro IFN-γ responses induced by PPDB and ESAT-6 in five animals experimentally infected with M. bovis. Blood samples were stimulated in vitro with antigen (4 μg/ml) for IFN-γ responses, and antigens (100 μg) were injected intradermally at separate sites in the cervical skin for skin test responses. Results are presented as means (+ standard errors of the mean [error bars]) of ODI for IFN-γ responses and increases in skin thickness at 72 h postinjection for skin test responses. **, mean skin responses to PPDB and ESAT-6 significantly different (P < 0.01).