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The isotype of anti-Trypanosoma cruzi lytic antibodies present in sera obtained from patients with the chronic phase of Chagas' disease was determined. Serum samples were submitted to gel filtration in Sephacryl S-200, ion exchange chromatography in DEAE-cellulose, affinity chromatography with protein A and immunoadsorption with anti-human IgG-Sepharose. The results of these experiments showed that human anti-T. cruzi lytic antibodies are mainly located in the IgG isotype probably in the IgG1 and IgG2 subclasses.

Bloodstream trypomastigotes were isolated from blood of A/Sn mice 7 d after infection with 10(5) Trypanosoma cruzi Y strain. Red blood cells were removed by centrifugation and hypotonic shock and platelets and leucocytes by passage through a carboxy methyl cellulose column. Binding of trypomastigotes to the resin was prevented by including 10% normal mouse serum in the eluting buffer. In such conditions, more than 90% of the parasites applied to the column were recovered, free of white blood cells and platelets. A comparative study of the pre- and post-separation trypomastigotes showed that both had the same infecting capacity, ability to evade destruction by the complement system, and antigenic profile.