Distinct response kinetics of gamma interferon and interleukin-4 in bovinetuberculosis

This study shows that gamma interferon (IFN-gamma) and interleukin-4 (IL-4) cytokine responses are produced by peripheral blood cells in cattle infect ed with Mycobacterium bovis. The different kinetics of the IFN-gamma and IL -4 responses to bovine tuberculin and to ESAT-6 following experimental intr atracheal infection with M. bovis are described. An early increase in IFN-g amma was observed that was maintained throughout the period studied. In con trast, the IL-4 response was delayed and confined to a peak of activity las ting 6 to 8 weeks. Interestingly, an experimental challenge of cattle with a lower dose of M. bovis which did not result in the development of lesions , positive DTH skin test, or substantial IFN-gamma responses nevertheless g enerated strong specific IL-4 responses. Investigation of naturally infecte d M. bovis field reactors showed increased IFN-gamma and IL-4 responses com pared to uninfected cattle and that both of these cytokines were equally ab le to differentiate infected from uninfected animals. The magnitude of the M. bovis-induced IL-4 responses were found to be similar to the antigen-spe cific IL-4 responses of cattle infected with the parasitic nematode Onchoce rca ochengi, further supporting the presence of this type 2 cytokine in bov ine tuberculosis.