The role of antibody and complement in the cellular response to Trypanosoma congolense

The in vitro cytotoxic response of bovine granulocytes and monocytes and of murine peritoneal macrophages against Trypanosoma congolense in the presence of antibody, antibody plus complement or complement alone was assessed using luminol aided chemiluminescence as a second parameter for effector cell activation. Neither cell type exhibited any trypanolysis exceeding that of antibodies and complement alone. The kinetics of the chemiluminescence response in the course of these reactions closely correlated with the trypanocidal activity of the antibody preparation used, suggesting effector cell activation as a response to antibody-mediated immobilization and damage of the trypanosomes. From these results and electron microscopic investigations we conclude that antibody- or complement-dependent cell-mediated cytotoxic reactions do not play a significant role in the defence of T. congolense infection, neither by extracellular lysis nor killing of ingested parasites.