title: In vivo approaches reveal a key role for DCs in CD4+ T cell activation and parasite clearance during the acute phase of experimental blood-stage malaria.
abstract: Dendritic cells (DCs) are phagocytes that are highly specialized for antigen presentation. Heterogeneous populations of macrophages and DCs form a phagocyte network inside the red pulp (RP) of the spleen, which is a major site for the control of blood-borne infections such as malaria. However, the dynamics of splenic DCs during Plasmodium infections are poorly understood, limiting our knowledge regarding their protective role in malaria. Here, we used in vivo experimental approaches that enabled us to deplete or visualize DCs in order to clarify these issues. To elucidate the roles of DCs and marginal zone macrophages in the protection against blood-stage malaria, we infected DTx (diphtheria toxin)-treated C57BL/6.CD11c-DTR mice, as well as C57BL/6 mice treated with low doses of clodronate liposomes (ClLip), with Plasmodium chabaudi AS (Pc) parasites. The first evidence suggesting that DCs could contribute directly to parasite clearance was an early effect of the DTx treatment, but not of the ClLip treatment, in parasitemia control. DCs were also required for CD4+ T cell responses during infection. The phagocytosis of infected red blood cells (iRBCs) by splenic DCs was analyzed by confocal intravital microscopy, as well as by flow cytometry and immunofluorescence, at three distinct phases of Pc malaria: at the first encounter, at pre-crisis concomitant with parasitemia growth and at crisis when the parasitemia decline coincides with spleen closure. In vivo and ex vivo imaging of the spleen revealed that DCs actively phagocytize iRBCs and interact with CD4+ T cells both in T cell-rich areas and in the RP. Subcapsular RP DCs were highly efficient in the recognition and capture of iRBCs during pre-crisis, while complete DC maturation was only achieved during crisis. These findings indicate that, beyond their classical role in antigen presentation, DCs also contribute to the direct elimination of iRBCs during acute Plasmodium infection.
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil; Instituto Gulbenkian de Ciência, Oeiras, Portugal.
authors: Henrique
authors: H
authors: Borges da Silva
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: Raíssa
authors: R
authors: Fonseca
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: Alexandra Dos Anjos
authors: Ados A
authors: Cassado
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: Érika
authors: É
authors: Machado de Salles
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: Maria Nogueira
authors: MN
authors: de Menezes
authors: Medical Research Center, London, United Kingdom.
authors: Jean
authors: J
authors: Langhorne
authors: Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brasil.
authors: Katia Regina
authors: KR
authors: Perez
authors: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brasil.
authors: Iolanda Midea
authors: IM
authors: Cuccovia
authors: Unité d'Immunologie et Neurogénétique Expérimentales et Moléculaires (CNRS-UMR7355), Université d'Orléans, Orléans, France.
authors: Bernhard
authors: B
authors: Ryffel
authors: Instituto Gulbenkian de Ciência, Oeiras, Portugal.
authors: Vasco M
authors: VM
authors: Barreto
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: Cláudio Romero Farias
authors: CR
authors: Marinho
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: Silvia Beatriz
authors: SB
authors: Boscardin
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: José Maria
authors: JM
authors: Álvarez
authors: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors: Maria Regina
authors: MR
authors: D'Império-Lima
authors: Instituto Gulbenkian de Ciência, Oeiras, Portugal.
authors: Carlos Eduardo
authors: CE
authors: Tadokoro
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology*; D004195:Disease Models, Animal; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D008213:Lymphocyte Activation / Q000276:immunology*; D008288:Malaria / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D018512:Parasitemia / Q000276:immunology; D010587:Phagocytosis / Q000276:immunology; D016788:Plasmodium chabaudi; D013154:Spleen / Q000276:immunology / Q000469:parasitology