Reduction in the ability of Trypanosoma brucei to react with antibodies after long exposure to immune mechanisms in vivo

Department of Veterinary Microbiology and Immunology, University of Guelph, Ontario, Canada Received March 20, 1971 Accepted July 10, 1971 Antigenic studies on variants of Trypanosoma brucei isolated from infected rabbits at different intervals were carried out by agglutination and by opsonic adherence tests with corresponding antisera isolated from the same rabbits. Organisms isolated from infected rabbits 2 and 5 wk after infection were relatively inagglutinable by sera collected at the same time and 3 wk later from the rabbit from which the trypanosomes were derived. Experiments on adherence of trypanosomes to macrophages in the presence of antibodies indicated the lack of opsonic adherence particularly in the presence of a prozone. These results suggest possible antigenic loss in the presence of antibodies. * Research Fellow, Medical Research Council of Canada.