Double diffusion analysis of antigens released from Plasmodium knowlesi in vitro.

Two parasite-derived antigens (designated band 1 and band 2) were identified upon double-diffusion analysis of culture medium from reinvading culture of P. knowlesi. Band 1 antigen showed characteristics with the R-antigens of P. falciparum while the other was similar to the P. falciparum L-antigens. Both antigens appeared to be largely particulate in character and did not display any obvious variant-specificity. Analysis of plasma from rhesus monkeys infected with the same antigenic variant showed the presence of band 1 antigen only.