RESUMO
BACKGROUND & OBJECTIVES: Trypanosoma lewisi is a common, flagellated parasite of the rat. Our previous study showed that rabbits injected with serum collected from rats infected with Trypanosoma lewisi and treated with cyclophosphamide (CyI) produced high levels of antibodies against a new protein in the CyI rat serum. RESULTS: In the present study, this protein was characterised as alpha2 macroglobulin (alpha2M) and the kinetics of its production and its influence on the malignancy of the disease were determined. In rats infected with T. lewisi, alpha2M was first demonstrated and peaked on the second day post-infection (972 microg/ml) and then reduced gradually, reaching a level of 32 microg/ml on the eighth day post-infection. However, in the CyI rats the level of alpha2M was gradually increased as the disease progressed, reaching a level of 890 microg/ml on the eighth day post-infection. Injection of both crude and purified alpha2M into rats infected with T. lewisi led to increased parasitaemia. INTERPRETATION & CONCLUSION: The present study suggests that increased levels of alpha2M in the CyI rats contribute to the malignancy of the disease.