Involvement of cytokines in determining resistance and acquired immunity in murine tuberculosis

Herein we demonstrate that continuous infusion of either TNF-alpha or IFN-gamma (10(4) U/day) via osmotic micropumps leads to an increased resistance of mice infected with a lethal dose (10(7)) of M. tuberculosis H37Rv, associated with a decreased microbial growth in all target organs. This result was reinforced by the finding that infusion of antibodies against TNF-alpha or IFN-gamma greatly enhanced susceptibility of naive mice to tuberculosis. In a final set of experiments, using neutralizing antibodies, we show that IFN-gamma, not TNF-alpha is involved in determining acquired resistance against murine tuberculosis, as seen by the fact that acquired immunity is resistant to anti-TNF-alpha antibodies, yet sensitive to anti-IFN-gamma antibodies. This suggests a role for both IFN-gamma and TNF-alpha in determining innate resistance whereas IFN-gamma may be the mediator of the anamnestic response.