Immunity to Malaria Parasites.

Ring stages of P. falciparum were cryopreserved by snapfreezing in liquid nitrogen using glycerol as cryoprotectant. Gametocytes of P. falciparum differentiated over 8-10 days from ring stages put into culture and also from merozoites released in culture. Gametocytes grew less well in cells containing HbF. P. malariae in culture grew to the schizont stage only. Isolates of P. falciparum from 98 patients have been cryopreserved. Preliminary results confirmed earlier results that showed higher in vitro antiparasitic activity in post-treatment sera although a few promoted parasite growth. Increased numbers of K cells were detected in the spleens of P. chabaudi infected mice. Mice infected within two weeks of irradiation showed some non-specific resistance to P. chabaudi. Immune serum had enhanced activity in irradiated mice. Cyclophosphamide treatment before infection also depressed the early stages of the primary P. chabaudi parasitaemia. Adoptive transfer experiments confirmed the role of T cells in immunity to P. chabaudi. One role of the T cells is to act as helper cells.