Experimental infection of athymic mice with Toxoplasma gondii

Congenitally athymic nude mice and their hirsute littermates with thymuses were infected with a normally avirulent cyst-producing strain of Toxoplasma gondii. The nude mice were much less able to cope with the infection. Unlike their hirsute littermates they failed to produce any detectable antibody and apparently allowed faster multiplication of cysts in the brain where the normal inflammatory response was absent. It was concluded that the thymus plays an essential role in the development of immunity to a cyst-producing strain of Toxoplasma in mice and in its absence neither humoral nor cellular protective mechanisms can develop.