The phagocytosis by mouse peritoneal macrophages of parasitized red cells (PRCs) and nonparasitized red cells (nonPRCs) separated from Plasmodium berghei infected blood was studied in vitro. Peritoneal macrophages from acutely infected mice and normal mice were cultured on coverslips. PRCs and nonPRCs were fractionated by Ficoll density gradient centrifugation from Plasmodium berghei infected blood. PRCs were fed in triplicate cultures to normal macrophages in normal serum, normal macrophages in acute serum, acute macrophages in normal serum, and acute macrophages in acute serum. Similarly, nonPRCs were fed to macrophages in the same combinations of normal and acute macrophages and serum. In acute serum, acute macrophages ingest PRCs significantly more readily than normal macrophages (p less than 0.05). Acute macrophages in acute serum ingest PRCs more readily than acute macrophages in normal serum, but the difference does not achieve statistical significance. Acute serum apparently decreases the phagocytosis of PRCs and nonPRCs by normal macrophages, perhaps because of an inhibitory antibody present in acute serum. As with PRCs, in the presence of acute serum, acute macrophages ingest nonPRCs significantly more readily than normal macrophages (p less than 0.05).
