Immunopathogenesis of toxoplasmic encephalitis.

The incidence of toxoplasmic encephalitis (TE) has increased with the increasing numbers of patients with immunodeficiencies, in whom reactivation of latent Toxoplasma infection may occur. This highlights the important role of the immune response in maintaining infection with Toxoplasma gondii in a latent form. Because the brain is the most commonly affected site of latent infection and because it is anatomically unique in regard to the immune system, understanding the systemic immune response to infection within the brain is important. Murine models have proven useful for the study of the immune response to T. gondii and identified the importance of cytokines and NK and T cells in the regulation of protective immunity to T. gondii. Further studies on the development of TE have indicated the possible importance of the interactions of glial cells, such as microglia and astrocytes, with infiltrating T cells to mediate immunity to T. gondii within the brain.