Immunity in Experimental Toxoplasmosis*

The Beverley strain of Toxoplasma gondii produces a chronic infection in mice and other laboratory animals, causing few or no fatalities. There is an immune response to the parasite that can be detected by a variety of serological teclmiques, with however but little understandillg of the significance of the phemmenon. The purposes of these experiments were to determine: 1) the nature of this immune response, i.e., whether humoral, cellular, or a combination of both, 2) if this immune response would protect mice against a subsequent challenge with the highly virulent RH strain of Toxoplasma, 3) the time of onset, and duration of such protection, and 4) to compare the effects of infection with RH in immune