title: Intracellular survival of Leishmania major in neutrophil granulocytes after uptake in the absence of heat-labile serum factors.
abstract: The role of polymorphonuclear neutrophil granulocytes (PMN) in defense against the intracellular parasite Leishmania is poorly understood. In the present study, the interaction of human PMN with Leishmania major promastigotes was investigated in vitro. In the presence of fresh human serum, about 50% of PMN phagocytosed the parasites within 10 min and the parasite uptake led to PMN activation, resulting in the killing of most ingested parasites. Heat inactivation of the serum markedly reduced the rate of early parasite phagocytosis, suggesting a role of complement components in the early uptake of Leishmania. However, over 50% of PMN were able to ingest parasites in the presence of heat-inactivated serum if the coincubation was extended to 3 h. After 3 h, 10% of the PMN were found to internalize Leishmania even under serum-free conditions. These findings indicate that PMN possess mechanisms for both opsonin/complement-dependent and -independent uptake of Leishmania. Both pathways of uptake could be partially blocked by anti-CR3 antibody. Mannan-binding lectin was found not to be involved in this process. When phagocytosed in the absence of opsonin, the majority of Leishmania parasites survived intracellularly in PMN for at least 1 day. These data suggest a dual role of PMN in the early response to L. major infection. On the one hand, PMN can rapidly eliminate the intracellular parasites, and on the other hand, Leishmania can survive intracellularly in PMN. These data, together with the finding that intact parasites were seen in PMN isolated from the skin of infected mice, suggest that PMN can serve as host cells for the intracellular survival of Leishmania within the first hours or days after infection.
authors.affiliation: Institute for Medical Microbiology and Hygiene, Medical University of Lübeck, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Laufs
authors.forename: Kerstin
authors.initials: K
authors.lastname: Müller
authors.forename: Jens
authors.initials: J
authors.lastname: Fleischer
authors.forename: Norbert
authors.initials: N
authors.lastname: Reiling
authors.forename: Nicole
authors.initials: N
authors.lastname: Jahnke
authors.forename: Jens C
authors.initials: JC
authors.lastname: Jensenius
authors.forename: Werner
authors.initials: W
authors.lastname: Solbach
authors.forename: Tamás
authors.initials: T
authors.lastname: Laskay
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000276:immunology; D002478:Cells, Cultured; D037222:Collectins; D006361:Heating; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D007424:Intracellular Fluid / Q000469:parasitology; D037102:Lectins / Q000276:immunology; D018320:Leishmania major / Q000276:immunology*; D016177:Macrophage-1 Antigen / Q000276:immunology; D051379:Mice; D009504:Neutrophils / Q000166:cytology / Q000276:immunology* / Q000469:parasitology; D009895:Opsonin Proteins / Q000276:immunology; D010587:Phagocytosis / Q000276:immunology*; D016897:Respiratory Burst
chemical_list: D002352:Carrier Proteins; D037222:Collectins; D016209:Interleukin-8; D037102:Lectins; D016177:Macrophage-1 Antigen; D009895:Opsonin Proteins