Serum complement levels in asymptomatic Plasmodium falciparum parasitaemic children.

Twenty-eight (42%) of 67 afebrile children (mean age 6.3 +/- 3.6 years) undergoing various minor elective surgeries were slide positive for malaria parasitaemia. All infected subjects were given oral chloroquine therapy before and after blood samples were collected. Pre- and post-treatment complement (C4, C3, Bf and CH50 levels were evaluated in 15 of the subjects who had parasite densities > or = 500/microliter. These were compared with the levels in 15 age/sex-matched children who had acute malaria, as well as with the levels in 15 age/sex matched, non-infected controls. Significant consumption of C4 was observed in both the asymptomatic (p < 0.05) and symptomatic (p < 0.05) subjects. The mean serum levels of C4 were significantly higher in the asymptomatic, when compared with the symptomatic subjects (p < 0.01), and the healthy controls (p < 0.05). The distribution of classical pathway complement haemolytic titres in the groups studied was the same as that of the C4 levels. It is concluded that the forth component of the classical complement pathway may play a protective role in asymptomatic malaria.