The use of CFSE stained- L. chagasi to evaluate parasite-canine macrophage interaction. L. chagasi promastigotes were stained with the intracellular dye CFSE and the efficiency of the staining procedure evaluated trough flow cytometry (A) and conventional fluorescence microscopy (B). CFSE-stained parasites were used for in vitro infection of peritoneal dog macrophages (X to Y ratio) and the parasite-macrophage interaction was evaluated through flow cytometry. Macrophages were selected based on forward- versus side-scatter parameters (C) and the frequency and intensity of CFSE+ macrophages was evaluated (D to F – MI Marker). At least 30,000 events were collected. (D) Non-infected macrophages. (E) Macrophages infected by CFSE-stained parasites in absence of C5 deficient sera. (F) Macrophages infected by CFSE-stained parasites in presence of C5 deficient sera. Data represents the mean ± SE of the frequency of infected macrophages and the CFSE fluorescence intensity of infected macrophages, obtained for one dog, representing identical experiments of four dogs.