title: [Phagocytosis of promastigotes and amastigotes of Leishmania mexicana by the FSDC dendritic cell line: ultrastructural study].
abstract: BACKGROUND
  Dendritic cells, which capture and present antigen to activate unprimed T cell, are found in most tissues.
  
  
  OBJECTIVE
  This work describes the ultrastructure of Leishmania mexicana phagocytosis by the fetal skin dendritic cell (FSDC) line, a Langerhans cell line isolated from mouse fetal epidermis immortalized by retroviral transduction of the v-myc oncogene.
  
  
  METHODS
  Leishmania amastigotes were obtained from mouse (BALB/c) lesion and promastigotes from culture (24 degrees C) of the lesion. FSDC cells were cultured with parasites (5 parasites per cell) using IMDM medium, during 24 hours. Control and infected cultures were processed for transmission electron microscopy. Semi-thin sections counterstained with toluidine blue to evaluate phagocytosis and thin sections counterstained with uranyl acetate and lead citrate were made.
  
  
  RESULTS
  13.42% of the FSDC phagocytosed promastigotes; 8% contained a single parasite and 5.2% phagocytosed 2 or more. 20% of the FSDC phagocytosed amastigotes; 10% contained a single parasite and 10% phagocytosed 2 or more. Ultrastructurally, promastigotes in contact with FSDC by the flagellum or the posterior pole were observed. The parasitophorous vacuoles harbouring promastigotes were small organelles containing one or two parasites each. Parasitophorous vacuoles containing amastigotes were larger (8 microm diameter) with one or several parasites free or attached to the vacuole at the posterior pole.
  
  
  CONCLUSIONS
  The low rate of infected FSDC cells was characteristic and the parasitophorous vacuole showed similar characteristics to those observed in macrophages. The parasite density in the infected cells was 1 to 3 parasites per cell. These observations highlight the need to study the relationship between phagocytic capacity and function.
authors.affiliation: Unidad de Microscopía y Análisis de Imágenes, Instituto Nacional de Salud, Bogotá, D.C., Colombia. lsarmiento@ins.gov.co
authors.forename: Ladys
authors.initials: L
authors.lastname: Sarmiento
authors.forename: Martha
authors.initials: M
authors.lastname: Ayala
authors.forename: Sandra
authors.initials: S
authors.lastname: Peña
authors.forename: Gerzaín
authors.initials: G
authors.lastname: Rodríguez
authors.forename: Zelandia
authors.initials: Z
authors.lastname: Fermín
authors.forename: Felix J
authors.initials: FJ
authors.lastname: Tapia
mesh_terms: D000818:Animals; D002460:Cell Line; D003713:Dendritic Cells / Q000502:physiology* / Q000648:ultrastructure*; D007894:Leishmania mexicana / Q000648:ultrastructure*; D010587:Phagocytosis / Q000502:physiology*