Serum IgG, IgM, and C3 levels in Schistosoma japonicum infected rabbits

New Zealand white rabbits were infected with 250 or 500 Schistosoma japonicum cercariae of Philippine-Leyte strain. Following the initial pre-infection bleed, blood was collected 2, 4, 6, 8, 11, 14, 17, 20, 23, 26, 29, and 32 weeks post-infection, and IgG, IgM, and C3 levels were assayed in the serum samples by single radial immunodiffusion. IgG and IgM achieved peak levels at 14 weeks post-infection and began to decrease in concentration by 26 weeks. At 32 weeks, some of the infected rabbits exhibited significantly reduced IgG and IgM levels which approached the concentrations assayed in the control animals. The infected animals demonstrated significantly elevated C3 levels (p less than or equal to 0.001) during the 6th to 26th weeks post-infection, with the exception of the 20th week.