T lymphocyte-dependent effector mechanisms of immunity to Toxoplasma gondii.

Immunity to the opportunistic pathogen, Toxoplasma gondii, is highly dependent upon the effector activity of IFN-gamma-producing T lymphocytes. While IFN-gamma is required to survive infection, an understanding of its function remains incomplete. During infection, T. gondii simultaneously induces downregulatory antiinflammatory cytokines, thereby avoiding major host pathology mediated by proinflammatory cytokines such as IFN-gamma. The ability to induce the correct balance between these two opposing host responses likely accounts for the success of this organism as a parasite.