Explasmodial antigens of Plasmodium gallinaceum were analyzed electrophoretically and found to consist of two fractions. Fluorescein-labeled antibody against explasmodial antigen was used to stain erythrocytes from chickens acutely infected with P. gallinaceum. In erythrocytes containing immature parasites, fluorescence was confined to the parasites only, whereas in erythrocytes containing mature schizonts, diffuse fluorescence of the entire erythrocyte was observed. The FA reaction was prevented by treatment of erythrocytes with nonconjugated anti-explasmodial globulin before treatment with conjugated globulin.
In vitro exposure of erythrocytes from chickens acutely infected with P. gallinaceum to hyperimmune explasmodial serum resulted in agglutination and lysis of infected erythrocytes, which resulted in liberation of the parasite. Inoculation of freed parasites in susceptible chickens resulted in P. gallinaceum infection.
Antibody to explasmodial antigen enhanced in vitro phagocytosis of normal chicken erythrocytes by mouse reticuloendothelial cells. Indirect evidence of similar in vivo activity of this antibody was also obtained.