TABLE 4.

IFN-γ responses to crude mycobacterial antigens upon experimental infection

Infection statusIFN-γ responsea to recall antigen (WCS):
M. bovis strain 1315M. avium strain 3988M. avium subsp. paratuberculosis strain K10
Noninfected−0.7 (0.4) A−1.0 (0.4) A−0.8 (0.4) A
M. bovis-infected60.0b (2.5) C15.2 (0.9) B9.2 (0.7) B
M. avium-infected13.1 (2.4) B29.6b (2.9) C16.8 (2.5) C
M. avium subsp. paratuberculosis-infected17.0 (5.2) B22.7 (7.5) BC30.9 (11.6) BC
  • a IFN-γ responses (whole-blood assay) were unaffected (P > 0.05) by the length of postinfection period. For this reason, values are the mean IFN-γ responses (in nanograms per milliliter) (i.e., response to 20 μg of antigen per ml) minus their response to medium alone after 48 h) during the period spanning 4 to 7 months postinfection. Treatment groups consisted of four animals except for the M. avium subsp. paratuberculosis-infected group, which had three animals. Values in parentheses are the standard errors of the means.

  • d Letters A to C indicate that the treatment means for a specific type of stimulation (i.e., vertical comparisons) differ (P < 0.05). The same letter indicates that the IFN-γ responses were not significantly different (P < 0.05).

  • b Significantly different from the responses by the other cattle infected with M. bovis or M. avium (i.e., horizontal comparisons) (P < 0.05).