Ixodes ticks: serum species sensitivity of anticomplement activity

Ixodid ticks feed for extended periods of up to 2 weeks or more. To complete engorgement, they must overcome their host's innate immune mechanisms of which the complement system is a major component. Using in vitro assays, salivary gland extracts of the ixodid ticks, Ixodes ricinus, I. hexagonus, and I. uriae, were shown to inhibit activity of the alternative pathway of complement. The ability of the different Ixodes species to inhibit complement activity varied with the animal species used as a complement serum source. Serum species sensitivity correlates to the reported host range of the tick species tested.