PMNs do not phagocytose late-stage pRBCs or hemozoin in nonimmune serum. (A) pRBCs were stained with BCECF-AM, a nonfluorescent acetoxymethylester that is enzymatically hydrolyzed to fluorescent BCECF, to visualize parasites and intracellular DVs, and incubated with PE-labeled PMNs in active human serum. No erythrophagocytosis could be discerned after 30 minutes. Scale bar indicates 20 μm. (B) DVs were disrupted by sonication and hemozoin was isolated from a Percoll gradient and incubated with PMNs in active serum. No evidence for phagocytic uptake and no appearance of cells with characteristic malaria pigment could be discerned in Giemsa-stained smears. Scale bar indicates 10 μm. (C) Luminol-based chemiluminescence assay were performed in PMNs and active serum upon incubation with intact DVs or with sonicated DVs (hemozoin). Representative results are shown from 1 of 3 similar experiments.