Skin test specificity of a defined protein cocktail in naïve and BCG-vaccinated cattle. Skin test responses were measured for the protein cocktail comprised of ESAT-6, CFP-10, MPB70, and MPB83 (10 μg for each component) and for the SICCT test (PPD-B − PPD-A) in naïve TB-free (n = 19) and BCG-vaccinated (n = 20) cattle. Responses measured at 72 h for each animal are represented by open circles, and the horizontal line provides the mean (±SEM), with results expressed as the difference in skin thicknesses (mm) between the pre- and post-skin test readings.