Immunoglobulin G3 antibodies specific for the 19-kilodalton carboxyl-terminal fragment of Plasmodium yoelii merozoite surface protein 1 transfer protection to mice deficient in Fc-gamma RI receptors

Merozoite surface protein 1 (MSP-1(19)) is a leading malaria vaccine candid ate. Specific antibodies contribute to immunity; binding to macrophages is believed to represent the main action of malaria antibodies. We show that a n MSP-1(19)-specific immunoglobulin G3 (IgG3) monoclonal antibody can passi vely transfer protection to mice deficient in the alpha chain of Fc-gamma R I whose macrophages cannot bind IgG3.