FIG. 4.

Effects of the skin test on in vitro IFN-γ production by individual M. kansasii-sensitized cattle in response to mycobacterial antigens. Blood mononuclear cells were isolated from M. kansasii-infected cattle at the indicated time points after challenge (x axis) and cultured for 48 h with medium alone, 1 μg/ml rESAT-6-CFP-10, or 5 μg/ml PPDs, and supernatants were harvested for analysis of IFN-γ by ELISA. Values are presented as individual responses (in the key, numbers next to symbols refer to the animals' numbers) to rESAT-6-CFP-10 (A) or M. bovis PPD (B) stimulation (stim.) minus the response to the medium alone. Arrows below “CFT” and “CCT” indicate time points of injection of PPDs for the caudal fold and comparative cervical skin tests, respectively.