Changes in complement C3 levels following treatment of patients with Brugia malayi infection

Serum IgG levels and complement C3 levels were assayed on Day 0, 1, 3-4, 7 and 56-70 post-treatment with diethylcarbamizine citrate (DEC) in a series to 26 patients with Brugia malayi infection and 6 volunteers without infection. On treatment, the microfilariae were cleared from the blood within 24 hours. The eosinophils decreased dramatically on Day 1 post-treatment but increased rapidly by Day 4 to 7 and then dropped to normal levels in 45 days. The serum IgG mean levels decreased briefly following treatment with DEC but then returned to original levels. However, the complement C3 levels gradually increased over the 2 months period of study reaching statistical significance levels (p less than 0.01) in patients with initial high blood microfilariae. The observation suggests that Brugia malayi infection probably induces a high rate of synthesis of complement C3 and this process continued in the post-treatment phase. Since, DEC treatment did not cause a decrease in complement C3 with the elimination of blood microfilariae, it would appear that the complement C3 is consumed following antibody attachment to the microfilariae as they enter the blood circulation.