The response to Trypanosoma congolense infection in calves. Determination of immunoglobulins igG1, igG2, igM and C3 levels and the complement fixing antibody titres during the course of infection.

Serum immunoglobulins, IgG1, IgG2, IgM and C3 levels and the complement fixing antibody titres were determined over a period of 15 to 18 weeks in 13 calves infected with Trypanosoma congolense. The mean IgM concentration increased from 2.88 mg/ml prior to infection to 23.75 mg/ml at the 3rd week after infection. This level dropped by the 5th week but elevated values of 13-19 mg/ml were maintained until the end of the experiment. The mean IgG1 level increased from 10.55 mg/ml to a peak of 26.90 mg/ml by 7 weeks. After the 10th week, levels remained in the range of 12-15 mg/ml. There was only slight increase in mean IgG2 after 7 weeks infection with the highest mean value of 17.09 mg/ml as compared to 10.70 mg/ml of control animals occurring at the 13th week. The mean C3 concentration decreased from 3.75 mg/ml to 0.95g/ml by 2 weeks and fluctuating low levels were maintained for the duration of the infection. The appearance of CF antibody, the decrease in C3 at about 1 to 2 weeks post infection and the subsequent drops in the CF titres and C3 at 5-6, 8 and 11 weeks were each coincident with the drops in packed cell volume.