Mice treated late with 0.1 mg of anti-CD41 mAb during P berghei infection are not protected from severe P berghei malaria, whereas early anti-CD41 mAb treatment does protect. The cumulative survival (A) and average P berghei parasitemia ± SD (B) in groups of 10 mice injected intraperitoneally on day 1 with 0.1 mg anti-CD41 mAb on day 1, 4, 5, or 6 of infection. • indicates anti-CD41 day 1; ▴, anti-CD41 day 4; ▾, anti-CD41 day 5; ♦, anti-CD41 day 6; ▪, PBS day 4.