Fig. 1. Mechanisms of entry of L. amazonensis metacyclic promastigotes into macrophages. (A,B) Microcinematography of phagocytic events. Promastigote cell bodies and flagella are indicated by white arrowheads and white arrows, respectively. (A) Parasite attachment occurs by the cell body. The promastigote is then progressively internalized through the formation of a long tubular pseudopod (black arrowheads). (B) The parasite binds to the macrophage via the tip of the flagellum. It then turns around, so that its cell body comes into contact with the cell surface of the macrophage. Ruffles are formed at this site (black arrowheads). The promastigote is finally ingested via the cell body. The numbers indicated in the right hand corners correspond to the time (in seconds) elapsed from the first contact of promastigotes with macrophages (time 0). QuickTime movie sequence versions of A and B are available online (http://jcs.biologists.org/supplemental ). (C,D) Scanning electron micrographs showing the internalization of promastigotes via the formation of a closely apposed pseudopod (C) or of ruffles (D). Macrophages were fixed after 10 minutes of contact with the parasites. Bars, 10 µm (A,B), 1 µm (C,D).