Waterkeyn, JG, Cowman, AF, and Cooke, BM 2001. Plasmo- used method for purification of RBCs infected with mature-stage para-dium falciparum: Gelatin enrichment selects for parasites with full- sites. Furthermore, in contrast to Percol, gelatin also appears to maintain length chromosome 2. Implications for cytoadhesion assays. Experi- the adhesive phenotype of PRBCs that can be lost when most labora-mental Parasitology 97, 115–118. 2001 Academic Press tory-adapted parasite lines are maintained in long-term in vitro culture. Index Descriptors and Abbreviations: Plasmodium falciparum; ma- Maintenance of an adhesive phenotype is particularly important laria; red blood cell (RBC); parasitized red blood cell (PRBC); knobs; for laboratories that rely on the use of cultured lines to study the cytoadherence; knob-associated histidine-rich protein (KAHRP); mero- fundamentally important process of adhesion of PRBCs to the vascular zoite surface protein 4 (MSP4); packed cell volume (PCV); pulsed- endothelium, a pivotal event in the pathogenesis of severe falciparum field gel electrophoresis (PFGE); Plasmodium falciparum erythrocyte malaria (Cooke and Coppel 1995; Chen et al. 2000). It has become membrane protein 3 (PfEMP3); transmission electron microscopy part of malaria folklore that the mechanism by which adhesion is (TEM). maintained is due to the ability of gelatin to selectively separate only those PRBCs that express electron-dense knobs on their surface, although this has never been formally demonstrated. Nevertheless, this mechanism is supported by the fact that cultures of knobless PRBCs cannot be separated from uninfected RBCs in gelatin. When suspended in solutions of high-molecular-weight polymers or large molecules