Antigen-induced interferon-γ and interleukin-2 responses of cattle inoculated with Mycobacterium bovis

Bovine purified protein derivative (PPD)-induced interferon-γ (IFN-γ) and interleukin-2 (IL-2) mRNA expression was measured in peripheral blood lymphocyte cultures of cattle inoculated with Mycobacterium bovis and compared to cytokine protein levels as measured by IFN-γ enzyme-linked immunosorbent assay and IL-2 bioassay. For individual animals, positive correlations were observed between mRNA and protein levels of bovine PPD-induced IFN-γ and IL-2, although the correlations were stronger for IFN-γ. Expression of these two cytokines also correlated with responses from a comparative intradermal test and a M. bovis antibody test. At 7 and 20 weeks after inoculation, bovine PPD-induced IFN-γ and IL-2 mRNA expression was detected in all animals with tuberculous lesions and in a proportion of the M. bovis-inoculated animals with no lesions. Correlation of antigen-induced IFN-γ and IL-2 with other immune parameters suggests that these two cytokines play an important role in the immune response to bovine tuberculosis.