mAb 1B9 Immunofluorescence of merozoite invasion. Thin smears were incubated with mAb IB9, FITC-goat anti-mouse IgG and counterstained with ethidium bromide. (A and C) to identify parasite nucleus. (A) Merozoites attached to erythrocytes. Erythrocyte at upper right has been invaded by two merozoites. (B) Merozoites in the process of invading; rhoptry protein is discharged around erythrocyte surface. (C) Erythrocytes invaded by merozoites. Rhoptry protein is localized in infected erythrocyte membrane. Sam-Yellowe TY, Shio H, Perkins ME. Secretion of Plasmodium falciparum rhoptry protein into the plasma membrane of host erythrocytes. J Cell Biol. 1988.