Plasmodium berghei: relative immunogenicity of infected reticulocytes and infected oxyphilic red blood cells

Hyperbleeding of mice 1 day before and 1 day after infection with Plasmodium berghei resulted in a more aggravated infection. Parasitemia rose significantly faster, but the mean survival time of these mice was not significantly different from control mice. At Day 5 of infection, parasites were almost exclusively in reticulocytes in contrast to control infections in which parasites were found in oxyphilic erythrocytes at Day 5 after infection. Purified parasitized reticulocytes taken from hyperbled mice at Day 5 after infection contained more young developmental parasite stages than purified parasitized oxyphilic erythrocytes taken from normal mice at Day 5 to 7 after infection. Parasitized reticulocytes were more readily opsonized by antibodies from immune serum when compared to parasitized oxyphilic red blood cells and when used to stimulate immune spleen cells the former were better stimulator cells than the latter. Results suggest either that parasitized reticulocytes are more immunogenic then parasitized oxyphilic red blood cells or that suspensions of parasitized reticulocytes contain more immunogenic parasite stages than suspensions of parasitized oxyphilic red blood cells.