The complement profile in babesiosis.

Rats have been infected with Babesia rodhaini, a protozoan agent that induces immune complex disease. Assays for complement have revealed depletion of C2, C3, C4, C5, and whole complement in the course of infection. No evidence of depletion in the alternative (properdin) pathway was found. These findings are consistent with the conclusion that the classical complement pathway is activated during the course of the protozoan infection.