Immunoelectron microscopic localization of the rhoptry protein using mAb 1B9 and protein A-gold. (A) post-embedded immunolabeling of mature schizont-infected erythrocyte showing localization of 5-nm gold particles over rhoptries. EM, Erythrocyte membrane; SM, schizont membrane; FM, free merozoite; R, rhoptries. (Inset) High magnification of paired rhoptry organelles showing localization of rhoptry antigen. (B) concentric membranous whorls from preembedded sample. Protein A-gold particles of 20 nm are shown distributed around the concentric lamellae (arrows). (C) Post-embedded immunolabeling of ring-stage parasites (Ri). Gold particles of 5 nm are distributed around the parasite and over the erythrocyte cytoplasm. Bars, 500 nm. Sam-Yellowe TY, Shio H, Perkins ME. Secretion of Plasmodium falciparum rhoptry protein into the plasma membrane of host erythrocytes. J Cell Biol. 1988 PMID: 2453514