title: Exposure to Leishmania braziliensis triggers neutrophil activation and apoptosis.
abstract: BACKGROUND
  Neutrophils are the first line of defense against invading pathogens and are rapidly recruited to the sites of Leishmania inoculation. During Leishmania braziliensis infection, depletion of inflammatory cells significantly increases the parasite load whereas co-inoculation of neutrophils plus L. braziliensis had an opposite effect. Moreover, the co-culture of infected macrophages and neutrophils also induced parasite killing leading us to ask how neutrophils alone respond to an L. braziliensis exposure. Herein we focused on understanding the interaction between neutrophils and L. braziliensis, exploring cell activation and apoptotic fate.
  
  
  RESULTS
  Inoculation of serum-opsonized L. braziliensis promastigotes in mice induced neutrophil accumulation in vivo, peaking at 24 h. In vitro, exposure of thyoglycollate-elicited inflammatory or bone marrow neutrophils to L. braziliensis modulated the expression of surface molecules such as CD18 and CD62L, and induced the oxidative burst. Using mCherry-expressing L. braziliensis, we determined that such effects were mainly observed in infected and not in bystander cells. Neutrophil activation following contact with L. braziliensis was also confirmed by the release of TNF-α and neutrophil elastase. Lastly, neutrophils infected with L. braziliensis but not with L. major displayed markers of early apoptosis.
  
  
  CONCLUSIONS
  We show that L. braziliensis induces neutrophil recruitment in vivo and that neutrophils exposed to the parasite in vitro respond through activation and release of inflammatory mediators. This outcome may impact on parasite elimination, particularly at the early stages of infection.
authors.affiliation: Centro de Pesquisas Gonçalo Moniz, FIOCRUZ, Salvador, Bahia, Brazil.
authors.forename: Sarah A C
authors.initials: SA
authors.lastname: Falcão
authors.affiliation: Department of Biochemistry, and WHO-Immunology Research and Training Center, University of Lausanne, Epalinges, Switzerland.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Weinkopff
authors.affiliation: Department of Biochemistry, and WHO-Immunology Research and Training Center, University of Lausanne, Epalinges, Switzerland.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Hurrell
authors.affiliation: Centro de Pesquisas Gonçalo Moniz, FIOCRUZ, Salvador, Bahia, Brazil.
authors.forename: Fabiana S
authors.initials: FS
authors.lastname: Celes
authors.affiliation: Centro de Pesquisas Gonçalo Moniz, FIOCRUZ, Salvador, Bahia, Brazil.
authors.forename: Rebecca P
authors.initials: RP
authors.lastname: Curvelo
authors.affiliation: Departamento de Biomorfologia, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Salvador, Bahia, Brazil.
authors.forename: Deboraci B
authors.initials: DB
authors.lastname: Prates
authors.affiliation: Centro de Pesquisas Gonçalo Moniz, FIOCRUZ, Salvador, Bahia, Brazil; Instituto de Investigação em Imunologia, Salvador, Bahia, Brazil.
authors.forename: Aldina
authors.initials: A
authors.lastname: Barral
authors.affiliation: Centro de Pesquisas Gonçalo Moniz, FIOCRUZ, Salvador, Bahia, Brazil; Instituto de Investigação em Imunologia, Salvador, Bahia, Brazil.
authors.forename: Valeria M
authors.initials: VM
authors.lastname: Borges
authors.affiliation: Department of Biochemistry, and WHO-Immunology Research and Training Center, University of Lausanne, Epalinges, Switzerland.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Tacchini-Cottier
authors.affiliation: Centro de Pesquisas Gonçalo Moniz, FIOCRUZ, Salvador, Bahia, Brazil; Instituto de Investigação em Imunologia, Salvador, Bahia, Brazil.
authors.forename: Camila I
authors.initials: CI
authors.lastname: de Oliveira
mesh_terms: D000818:Animals; D017209:Apoptosis; D018821:CD18 Antigens / Q000032:analysis; D005260:Female; D019041:L-Selectin / Q000032:analysis; D007891:Leishmania / Q000276:immunology*; D007892:Leishmania braziliensis / Q000276:immunology; D019272:Leukocyte Elastase / Q000096:biosynthesis; D008264:Macrophages / Q000276:immunology / Q000469:parasitology; D051379:Mice; D008807:Mice, Inbred BALB C; D018375:Neutrophil Activation; D020556:Neutrophil Infiltration / Q000276:immunology; D009504:Neutrophils / Q000276:immunology; D013481:Superoxides / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D018821:CD18 Antigens; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D019041:L-Selectin; D019272:Leukocyte Elastase