A histological and immunohistochemical study of the changes induced in the brains of white mice by infection with Toxoplasma gondii.

The topography and the severity of the brain lesions induced in male and female white mice 1-6 weeks following inoculation with Toxoplasma gondii were studied by conventional histological and peroxidase-antiperoxidase (PAP) immunohistochemical techniques. The medulla oblongata and fourth ventricle were the most severely damaged areas of the brain, while the cerebellum was only minimally involved in this only in the later stages of the disease. Toxoplasma cysts were revealed by the PAP method as early as 2 weeks after infection. The number of cysts and the severity of the lesions increased gradually each week following inoculation. The lymphoplasmacytic element in the lesions was less intense in male than in female mice. The significance of these findings in respect to the possible immunological pathogenesis of CNS toxoplasmic changes is discussed. A correlation of the experimental findings with the known neurologic manifestations of the disease is also attempted. The advantage of the PAP method in the study of toxoplasmic infection is stressed.