Immunity to malaria: the antibody response to antigenic variation by Plasmodium knowlesi.

Abstract

Monkey erythrocytes infected with schizonts of Plasmodium knowlesi are agglutinated when mixed with serum taken from chronically infected monkeys (Eaton, 1938). This reaction has proved highly specific and capable of distinguishing antigenic variants of one strain. Chronic infections of P. knowlesi in rhesus monkeys are maintained by a succession of antigenically distinct populations, each population stimulating a specific agglutinin response. Additional agglutinins which are not variant specific are found at low titre in sera taken after an infection has persisted for a month or more. The possible relevance of these observations to protective immunity is discussed.