Cutting edge: neutrophil granulocyte serves as a vector for Leishmania entry into macrophages.
Macrophages (MF) are the final host cells for multiplication of the intracellular parasite Leishmania major (L. major). However, polymorphonuclear neutrophil granulocytes (PMN), not MF, are the first leukocytes that migrate to the site of infection and encounter the parasites. Our previous studies indicated that PMN phagocytose but do not kill L. major. Upon infection with Leishmania, apoptosis of human PMN is delayed and takes 2 days to occur. Infected PMN were found to secrete high levels of the chemokine MIP-1beta, which attracts MF. In this study, we investigated whether MF can ingest parasite-infected PMN. We observed that MF readily phagocytosed infected apoptotic PMN. Leishmania internalized by this indirect way survived and multiplied in MF. Moreover, ingestion of apoptotic infected PMN resulted in release of the anti-inflammatory cytokine TGF-beta by MF. These data indicate that Leishmania can misuse granulocytes as a "Trojan horse" to enter their final host cells "silently" and unrecognized.
van Zandbergen
Ger
G
Institute for Medical Microbiology and Hygiene, University of Lübeck, Lübeck, Germany. Zandbergen@hygiene.ukl.mu-luebeck.de
Klinger
Matthias
M
Mueller
Antje
A
Dannenberg
Sonja
S
Gebert
Andreas
A
Solbach
Werner
W
Laskay
Tamás
T
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D002465:Cell Movement / Q000276:immunology; D054407:Chemokine CCL4; D006790:Host-Parasite Interactions / Q000276:immunology; D006801:Humans; D018320:Leishmania major / Q000276:immunology* / Q000648:ultrastructure; D019402:Macrophage Inflammatory Proteins / Q000096:biosynthesis; D008264:Macrophages / Q000276:immunology* / Q000469:parasitology* / Q000648:ultrastructure; D009000:Monocytes / Q000276:immunology / Q000469:parasitology / Q000648:ultrastructure; D009504:Neutrophils / Q000276:immunology* / Q000469:parasitology* / Q000648:ultrastructure; D010587:Phagocytosis / Q000276:immunology
D054407:Chemokine CCL4; D019402:Macrophage Inflammatory Proteins