Abstract
Monoclonal antibodies that react specifically with bradyzoite antigens of Toxoplasma gondii were selected by differential immunofluorescence among hybridomas produced against these organisms. These antigens were further characterized by immunofluorescence on living bradyzoites and Western immunoblotting. Four pellicular antigens (36, 34, 21, and 18 kDa) were identified; three of these are exposed on the surface of the organism and accessible to either antibodies, trypsin cleavage, or both of these surface-probing procedures. These antigens were found on recent human isolates of T. gondii, as well as on laboratory strain bradyzoites obtained from either brain cysts or in vitro-grown parasites.