Malarial antigens on infected erythrocytes.

Absorption experiments with washed membranes derived from erythrocytes infected with schizonts of Plasmodium knowlesi (PE) showed that the antigen responsible for agglutination of PE in SICA tests is firmly bound to membranes. Further experiments demonstrated that the number of antibody binding sites at the surface of parasitized erythrocytes can be measured using iodinated globulins. The conditions under which this could be achieved have been defined and a preliminary estimate of the number of high affinity surface antigen sites (greater than or equal to 10(4) per cell) has been made. Suggestions are given for further work to obtain a more accurate value.