Abstract
Group O Rh negative human erytocytes were coated with the semipurified fraction of T. cruzi proteinase and tested with sera both from patients with Chagas' disease and from others with the sera from the former and with that from two patients with mucocutaneous leishmaniasis. No crossed reactions were observed with visceral leishmaniasis, malaria, toxoplasmosis syphilis, schistomiasis or mononucleosis sera. Results suggest that this purified fraction can be used in immunodiagnosis of American trypanosomiasis.