Changes in fibroblast-derived trypomastigotes of Trypanosoma cruzi during long-term culture

Fibroblast-derived trypomastigotes (FDTs) of Trypanosoma cruzi that had been in culture for extended periods of time were found to differ in their ability to proliferate in culture when compared to blood-form trypomastigotes (BFTs) and FDTs that had been recently established from blood-forms. "Old" FDTs transform into amastigotes/spheromastigotes and epimastigotes and readily incorporate [3H]thymidine in medium alone or in the presence of mouse spleen cells, whereas "new" FDTs and BFTs did not incorporate [3H]thymidine although they did transform in culture. These differences should be considered when FDTs are used for physiologic and immunologic studies of T. cruzi.