Nature and location of Trypanosoma brucei subgroup exoantigen and its relationship to 4S antigen

Abstract It has been suggested that exoantigen of Trypanosoma brucei subgroup is not continuously secreted by trypanosomes in the bloodstream of hosts. The antigen was not detected in plasma collected quickly, but appeared in increasing quantities when blood was removed from the host and allowed to stand. Analysis of exoantigen by isoelectric focusing in polyacrylamide gel has shown it to be a heterogeneous antigen of at least three components with a common antigenic determinant. Each of the components is a protein carbohydrate complex, having an isoelectric point (pI) in the pH range 6.0–5.5. Evidence was presented suggesting that this antigen is identical to 4S antigen, AND has its main location as a major component of the surface coat of bloodstream forms of T. brucei subgroup. The name “surface antigen” has been proposed, AND a method for rapidly preparing it in an apparently fairly pure form from trypanosomal homogenates has been detailed.