Immunity to Plasmodium berghei in rats: passive serum transfer and role of the spleen.

Pools of rat antiserum to Plasmodium berghei had different levels of protective activity as assessed by a passive transfer test. Preincubation of parasite inocula with an effective pool before injection did not significantly enhance protective activity. Removal of the antiserum from preincubated parasite inocula abolished the bulk of protective activity. Similarly, antiserum effective in intact animals was largely ineffective in splenectomized recipients. These experiments suggest a minimal role for antibody acting directly on P. berghei-parasitized cells and reemphasize a significant role for the spleen in immunity to this plasmodium.