Soluble antigens released in vitro from erythrocytes infected with Plasmodium berghei.

Rat erythrocytes parasitized with Plasmodium berghei were found to release soluble antigenic products in vitro. The supernatants obtained by centrifugation of the disrupted cells induced specific transformation of non-adherent spleen lymphocytes of convalescent rats and produced precipitation lines with antiplasmodial antibodies. In a preliminary experiment they also immunized young rats against a viable challenge of P. berghei. It is suggested that the soluble material could serve for the purification of an effective protective antigen.