Immune responses in cattle inoculated with Mycobacterium bovis, Mycobacterium tuberculosis, or Mycobacterium kansasii

Cattle were inoculated with Mycobacterium bovis, Mycobacterium tuberculosis, or Mycobacterium kansasii to compare the antigen-specific immune responses to various patterns of mycobacterial disease. Disease expression ranged from colonization with associated pathology (M. bovis infection) and colonization without pathology (M. tuberculosis infection) to no colonization or pathology (M. kansasii infection). Delayed-type hypersensitivity and gamma interferon responses were elicited by each mycobacterial inoculation; however, the responses by the M. bovis- and M. tuberculosis-inoculated animals exceeded those of the M. kansasii-inoculated animals. Specific antibody responses were detected in all M. tuberculosis- and M. bovis-inoculated cattle 3 weeks after inoculation. From 6 to 16 weeks after M. tuberculosis inoculation, the antibody responses waned, whereas the responses persisted with M. bovis infection. With M. kansasii inoculation, initial early antibody responses waned by 10 weeks after inoculation and then increased 2 weeks after the injection of purified protein derivative for the skin test at 18 weeks after challenge. These findings indicate that antibody responses are associated with the antigen burden rather than the pathology, cellular immune responses to tuberculin correlate with infection but not necessarily with the pathology or bacterial burden, and exposure to mycobacterial antigens may elicit an antibody response in a presensitized animal.