(A) Course of P yoelii 17XNL (nonlethal) infection in intact (•; n = 2) and splenectomized (▪; n = 3) transgenic mice expressing 40% to 60% α₂^Mγ₂ hemoglobin. Mice were infected intraperitoneally with 1 × 10⁵ infected erythrocytes on day 0. On the days indicated, smears were prepared from the tail vein, stained, and counted. Data are expressed as mean parasitemia ± SEM. (B) Course of P yoelii 17XNL infection in C57BL/6J intact (○; n = 6) and splenectomized controls (□; n = 4). Mice were infected intraperitoneally with 1 × 10⁵ infected erythrocytes on day 0. On the days indicated, smears were prepared from the tail vein, stained, and counted. Data are expressed as mean parasitemia ± SEM.