Abstract
The protective mechanisms associated with resistance to atypical mycobacteria infections are not clear. In an effort to broaden our understanding of the mechanisms involved, susceptible mice were infected with a virulent strain of M. avium and various treatments were applied so as to modify the course of the disease. Treatment with an antiserum against tumour necrosis factor-alpha (TNF-alpha) significantly enhanced the experimental infection, as judged by enumeration of colony-forming units (CFU) in the spleens and livers of infected mice, suggesting a role for TNF-alpha in resistance to M. avium. In other sets of experiments, recombinant cytokines were directly infused into infected mice. Infusion of recombinant interferon-gamma (IFN-gamma) did not modify the experimental infection significantly, and infusion of interleukin-2 was also without effect. Injection of TNF-alpha enhanced resistance in susceptible animals, as seen by a reduction in the viable bacilli recovered from the spleens and livers. In a final set of experiments, we demonstrate that combinations of cytokines may induce strong resistance against M. avium, namely injection of 1 micrograms of interleukin-1 alpha and 1 micrograms of TNF-alpha at 5-day intervals which was seen to eradicate M. avium in both spleens and livers of susceptible BALB/c mice. Overall, our results suggest that induction of protection against M. avium by treatment with cytokines may be feasible, and that TNF-alpha may be a pivotal molecule in resistance to M. avium.