Role of spleen in morbidity and mortality of Plasmodium berghei infection in mice.

Splenectomy has a strain-specific effect on Plasmodium berghei infection in mice. Mean survival time either was unchanged or increased to three times the value observed in intact controls. A delay of early mortality, which was otherwise observed in the second week of infection, was a general feature of susceptible strains. Delayed mortality was also observed when splenectomy was performed shortly before expected mortality. Ineffectiveness of splenectomy as to increased survival time was independent of the infective dose. The morbidity of the infection was reduced or delayed. Liver pathology, as assayed by changes in serum glutamate oxaloacetate transaminase activity, was always reduced after splenectomy. Strains exhibiting increased survival time after splenectomy also showed reduced peak parasitemia and delayed thymus involution, enhanced reduction of hematocrit, and a more pronounced increase in liver weight during infection compared to intact controls and strains in which splenectomy did not prolong survival times. The effect of splenectomy on morbidity and mortality of a P. berghei infection was compared to its strain-specific effect on antibody production to heterologous erythrocytes. The possibility of a spleen-dependent (immuno)-pathological response induced by the parasite during primary infection contributing to death of the host is discussed.