title: Release of radio-isotope labelled antigens from Plasmodium knowlesi during merozoite re-invasion in vitro.
abstract: Labelled antigens sharing determinants with both membrane and cytoplasmic fractions of Plasmodium knowlesi were detected in culture medium after in vitro incubation of schizont-stage parasites previously pulse-labelled with [3H]isoleucine. Release of antigens occurred only during schizont rupture and merozoite re-invasion. Antigenic material accounted for up to a third of the total trichloroacetic acid-insoluble radioactivity released by the cells. Absorption experiments indicated that approximately two-thirds of this antibody-precipitable material shared determinants with parasite membrane antigens, with a similar quantity sharing determinants with cytoplasmic proteins. Using antisera derived against 2 different antigenic variants of P. knowlesi, no evidence for the release of variant-spcific antigens was obtained. Centrifugal analysis revealed that the majority of the radio-isotope labelled antigens were particulate in nature; however, some appeared to exist in true solution.
mesh_terms: D000818:Animals; D000941:Antigens / Q000032:analysis*; D002462:Cell Membrane / Q000276:immunology; D003593:Cytoplasm / Q000276:immunology; D000939:Epitopes; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D008253:Macaca mulatta; D008297:Male; D010961:Plasmodium / Q000254:growth & development / Q000276:immunology*
chemical_list: D000941:Antigens; D000939:Epitopes