Complement factors and circulating immune complexes in children with urinary schistosomiasis and asymptomatic malaria

Abstract

Scrum concentrations of circulating immune complexes (C1C), complement factors (Factor B, C4, C8) and comple-ment activities (CH50 and AH50) were determined in Nige-rian school children having urinary schistosomiasis with or without symptomatic malaria by polyethylene glycol precipitation method, single radial immunodiffusion and total hacmolytic activities respectively. One hundred and forty-seven children were rccruitcd from St. John's Pri-mary School, Mokola, Ibadan, Nigeria.# ovale only, mixed infection of P. ovale with P. falciparum or mixed infection of P. malariae with P. falciparum were found in subjects with asymptomatic malaria without urinary schistosomia-sis (M-USS) but P. malariae or P. falciparum was found in subjects with co-infection of urinary schistosomiasis and asymptomatic malaria (M + USS). Mean value of C4 con-centration was significantly reduced in M - USS subjects or subjects having both USS and asymptomatic malaria (M + USS) compared with non-infected controls. Serum concentration of Factor B(FB) was significantly reduced while AH50 was significantly increased in urinary schisosomiasis subjects without malaria (USS-M) com-pared with M-USS subjects or the controls. These obser-vations implied that complement system in USS-M sub-jects is activated predominantly via alternative pathway (APW) while complement system is activated via classical pathway (CPW) in M-USS or M+USS subjects. The switch of complement activation pathway from alternative type in USS-M subjects to classical type in M-USS subjects may explain the lower malaria parasite densities often found in children harbouring Schistosoma haematobium parasites.