Course of P yoelii 17XL (lethal) infection in C57BL/6J controls (○; n = 6) and transgenic mice expressing 40% to 60% α₂^Mγ₂ hemoglobin (•; n = 7). 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.