Complement changes in falciparum malaria infection.

Complement profiles were sequentially studied in 183 Thai adults infected with Plasmodium falciparum. On the first day of admission, CH50, C1q, C4 and C3 were low in 65%, 8%, 19% and 62% of cases, respectively. All patients with low C1q or C4 also had low C3 and CH50. Simultaneous reduction of C1q, C4, C3 and CH50 were found in 10 instances. Factor B was not reduced in any of the patients indicating that only the classical pathway is activated during acute falciparum malaria infection. The incidence and the degree of hypocomplementaemia were higher in patients with cerebral, renal and hepatic complications although significant difference was seen only for C3. After 3-4 days of effective anti-malarial treatment, normalization of C1q and C4 was found in almost all instances whereas C3 and CH50 remained low in 27% and 54% of the cases, respectively. Normalization of C3 was achieved at 4 weeks after discharge while low CH50 still persisted. The reasons for the persistently low CH50 remain unknown.