Inhibition of parasite growth by anti-MSP-1 antibodies. Growth of P. falciparum strain 3D7 was monitored via the activity of parasite-specific LDH. (A) Equal amounts of rabbit serum containing anti-p83 (αp83), anti-p30 (αp30), anti-p38 (αp38), and anti-p42 (αp42) antibodies of the relative titers indicated were assayed. Light columns, growth inhibition; dark columns, antibody titers. (B) Dependency of growth inhibition on serum concentration, which was lowered twofold, from 40 to 5%, in consecutive steps. Rabbit serum raised against E. coli ClpB served as a control. (C) Growth inhibition of antibodies purified by antigen affinity chromatography. The final concentrations of the antibodies in the assay are indicated. Error bars show standard deviations.