Immune mechanism facilitating clearance of Trypanosoma gambiense by IgG3 antibody from infected host.

The aggregation of trypansomes, immune adherence to macrophage and protection against infection of Trypanosoma gambiense are associated with IgG3 antibody. IgG3-mediated clumping trypanosomes are readily dissociated by the aid of complement to become free. Dissociation of the clumped trypanosomes in the equivalence area released approximately fifty percent of previous bound surface antigens. These antigens were capable of binding again to new IgG3 antibody. Experiments indicated that complement deposition altered functionally bivalent IgG3 antibody in the immune complex into a univalent one. Such event in the presence of complement is of great advantage to the infected host in killing pathogens in vivo, as it allows more antibodies to attach to surface antigens and subsequently initiate complement activity.