Immunoparasitology series: Intravascular schistosomes and

Schistosomes are exposed to a variety of immuno-logical effectors, such as host complement, in the bloodstream of their definitive hosts. The parasites are reported to possess a plethora of regulatory proteins, including molecules acquired from the host, which impede the complement cascade. Evidence for the presence of a surface C2-binding protein, a C3-binding protein and a C8- and C9-binding protein has been reported. In addition, a surface Fc receptor might bind immunoglobulin and limit its ability to fix complement. However, the actual protective role of these proteins in vivo remains unresolved. Complement proteins in the plasma act through a cascade of reactions to attack extracellular pathogens. The terminal components in the cascade are designed to create pores i