Plasmodium antigens external to the parasite but with the infected erythrocyte.

Three Plasmodium berghei exoantigens with apparent mol. wt. of 120, 31, and 13 kDa, found in infected erythrocytes by immunofluorescence, are further characterized. These antigens, synthesized in the late trophozoite and schizont stages, were released into the culture medium after schizont-infected erythrocytes were placed in culture; however, they were not found in the sera of infected animals. The 120-kDa antigen proved to be somewhat heat-stable, whereas the other two did not. A monoclonal antibody (MAb) recognizing the 13-kDa antigen cross-reacted with proteins from P. chabaudi and P. yoelii, whereas MAbs against the other two antigens reacted only with proteins from strains of P. berghei.