title: Leishmania amazonensis-dendritic cell interactions in vitro and the priming of parasite-specific CD4(+) T cells in vivo.
abstract: The progressive disease following Leishmania amazonensis infection in mice requires functional CD4(+) T cells, which are primed to a disease-promoting phenotype during the infection. To understand how these pathogenic T cells are generated and the role of dendritic cells (DCs) in this process, we use DCs of susceptible BALB/c and resistant C3H/HeJ mice to examine parasite-DC interactions in vitro as well as the effector phenotype of T cells primed by parasite-exposed DCs in vivo. Our results demonstrate that amastigotes and metacyclics efficiently enter and activate DCs of both genetic backgrounds. Infection with amastigotes fails to induce CD40-dependent IL-12 production, but rather potentiates IL-4 production in BALB/c DCs. Upon transfer into syngeneic recipients, amastigote-exposed BALB/c DCs prime parasite-specific Th cells to produce significantly higher levels of IL-4 and IL-10 than their C3H/HeJ counterparts. Transfer studies with IL-4(-/-) DCs indicate that this enhanced Th2 priming seen in BALB/c mice is partially due to the IL-4 production by amastigote-carrying DCs. These results suggest that L. amazonensis amastigotes may condition DCs of a susceptible host to a state that favors activation of pathogenic CD4(+) T cells, and thereby provide a new perspective on the pathogenesis of cutaneous leishmaniasis and protozoan parasite-host interactions in general.
authors.affiliation: Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: H
authors.initials: H
authors.lastname: Qi
authors.forename: V
authors.initials: V
authors.lastname: Popov
authors.forename: L
authors.initials: L
authors.lastname: Soong
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis; D003713:Dendritic Cells / Q000276:immunology* / Q000469:parasitology; D004198:Disease Susceptibility; D005260:Female; D007111:Immunity, Cellular; D007896:Leishmaniasis / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008817:Mice, Mutant Strains; D016513:Mice, SCID; D013045:Species Specificity; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology
chemical_list: D016207:Cytokines