Complement (C3) levels and activation in rabbits experimentally infected with Trypanosoma evansi

Rocket immunoelectrophoresis was used to monitor the levels of the third complement component (C3) in the blood of rabbits experimentally infected with Trypanosoma evansi. Although a reduction in the circulating levels of C3 was associated with C3 activation in rabbits with high levels of parasitaemia, there was no evidence for C3 activation in uninfected rabbits, rabbits with early-stage, light infections or rabbits cleared of infection by drug treatment. Host-tolerance to current infection and to re-exposure to the parasite are probably affected by such changes in C3.