Fig. 3

Phagocytosis of FCR3S1.2 pRBCs after opsonization with monoclonal anti-PfEMP1 antibodies. Antibodies were tested in serial dilutions between 20 and 160 μg/ml. Relative phagocytosis was calculated as the percentage of ethidium bromide THP-1 positive cells relative to the positive control (rabbit anti human red blood cells, ab34858, ABCAM, 1:100 dilution). The negative control (unopsonized) was media alone (no antibody added). Values shown are mean and standard deviation from triplicates. a Antibodies isotyped as IgG2b are depicted in purple and those isotyped as IgG2a are depicted in red. b Mouse monoclonal antibodies showing a prozone-like effect with phagocytosis increasing with initial increases in antibody concentration to then decrease when higher antibody concentrations were used. c A single mouse monoclonal antibody showing gradual increases in phagocytosis with increasing antibody concentrations. d A single mouse monoclonal antibody showing high and stable phagocytosis induction at all antibody concentrations, being the most effective even at low concentrations