Leishmania braziliensis promastigotes and amastigotes interact differently with host macrophages.

In vitro and in vivo ultrastructral studies reveal that the parasite entrance into the macrophage occurs by phagocytosis. The early stage of phagocytosis exhibited different ultrastructural characteristics in both forms of the parasite. Long and prominent projections from peritoneal exudate macrophages made focal contacts with the promastigote surface. The amastigotes, in turn, laid on cup-shaped extensions of the macrophage membrane. Later stages of the phagocytosis are characterized by progressive and complete engulfment of both promastigotes and amastigotes.