Immunity to intra-erythrocytic protoza.

Intra-erythrocytic inclusion bodies were seen in Giemsa-stained smears of peripheral blood from mice infected with Babesia microti. These bodies, which were probably the pyknotic remnants of dead protozoa, increased as parasitaemia fell and the animal recovered. It is suggested that a soluble mediator liberated by cells of the host during infection penetrates the red blood-cell and leads to degeneration of the parasite.