Immunosuppression in murine malaria. I. General characteristics.

BALB/c and (BALB/c×C57 BL) F hybrid mice infected with developed a marked parasitaemia which lasted for 2–3 weeks. Immunization with sheep erythrocytes during the period of parasitaemia resulted in greatly reduced antibody formation and in a marked reduction in the number of plaque-forming cells in the spleens of infected mice. The maximal degree of immunosuppression coincided with the peak of parasitaemia. Antibody response to human γ-globulin but not to keyhole limpet haemocyanin was also markedly reduced. Skin graft rejection and contact hypersensitivity were not impaired during the infection and spleen cells from malaria infected mice responded normally to phytohaemagglutinin. Spleens from malaria infected mice reconstituted the ability of lethally irradiated mice to respond to sheep erythrocytes about one-half as effectively as spleens from normal mice. These findings are compatible with the view that the suppression of the immune response to sheep erythrocytes occurring in mice infected with is related to a disturbance of macrophage function produced by the infection.