Comparison of immunoglobulins of normal animals and animals infected and immunized with Trypanosoma brucei

The immunoglobulins of normal rabbits and mice, and rabbits and mice infected and immunized with T. brace! have been compared. The methods used in the study included the biuret test for total protein estimation, zinc sulphate test for gamma-globulin determination and gel diffusion techniques for determining serum immunoglobulin levels. The proportions of the different serum protein fractions here obtained by electrophoresis while characterization of the immunoglobulins was done by gel chromatography and agglutination tests. In infected rabbits, the total protein content increased during the infection and there was a decrease in the proportion of albumin while the gamma-global ins increased both in proportion and absolute concentration. The serum IgG titre increased slightly, "but the titre increased markedly to more than 32 times the preinfection level within 3 weeks. The agglutinin titre of the sera rose to a peak at 3 weeks but started to decline by the fifth week. Agglutinin activity was found in the IgM fraction alone, up to 3 weeks after infection but thereafter it occurred in both IgG and IgM fractions. Attempts to immunize rabbits by infection and drug-treatment were unsuccessful and no changes occurred in the sera of test and control animals. In mice, homologous challenge with the infecting strain of T. brucei showed that the immunization procedure was more successful and also demonstrated the protective effect of antibody. The changes in the total serum protein contents were not marked but the relative proportion of albumin in the sera of immunized mice decreased after immunization, while both the beta- and gamma-globulins increased in proportion and absolute amounts. High agglutinin titres appeared within a week and reached a peak at 3 weeks. Agglutinin activity occurred in the IgM fraction only soon after immunization but by the fourth week, both IgG and IgM fractions contained agglutinating antibodies.