title: Macrophages at intermediate stage of maturation produce high levels of IL-12 p40 upon stimulation with Leishmania.
abstract: IL-12 is one of the main cytokines driving the immune response to a resistant phenotype in leishmaniasis and in several other diseases involving intracellular microbes. In this study, we investigated IL-12 production by mononuclear phagocytes at several developmental stages when stimulated with Leishmania major, L. amazonensis or L. chagasi. Bone marrow cells were cultured for 4-6 days in vitro in the presence of M-CSF, GM-CSF or IL-3. After density separation, only cells banding at the 40-50% Percoll interface, but not those at 20-40% or 50-80% interfaces, produced large amounts of IL-12 p40 when stimulated with LPS or live Leishmania promastigotes. However, only low levels of IL-12 p70 were produced under these conditions. The high IL-12 p40-producing cells could be similarly derived from mouse strains with different susceptibility to Leishmania. Quantitative analysis of monocyte/macrophage lineage marker expression, in combination with positive and negative selection, led to the conclusion that the high IL-12 p40-producing cells are macrophages at an intermediate stage of maturation between immature and fully differentiated cells, expressing ER-HR3 but only low levels of the mature markers, scavenger receptor and CD11b/Mac-1. They do not express any of the precursor markers CD31/ER-MP12, Ly-6C/ER-MP20 or ER-MP58. Because recruitment of monocytes to an infection site and its draining lymph node is a general phenomenon, the notion that, developing from these monocytes, a population of mononuclear phagocytes at an intermediate maturation stage has the capacity to synthesize large amounts of IL-12 p40 has significant bearing on our understanding of immune regulation in leishmaniasis and also in infections by other pathogens.
authors.affiliation: Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1730, CEP 05508-900, São Paulo SP, Brazil.
authors.forename: Milton A P
authors.initials: MA
authors.lastname: Oliveira
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Tadokoro
authors.forename: Glória M C A
authors.initials: GM
authors.lastname: Lima
authors.forename: Tainá
authors.initials: T
authors.lastname: Mosca
authors.forename: Leda Q
authors.initials: LQ
authors.lastname: Vieira
authors.forename: Pieter J M
authors.initials: PJ
authors.lastname: Leenen
authors.forename: Ises A
authors.initials: IA
authors.lastname: Abrahamsohn
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D018664:Interleukin-12 / Q000378:metabolism*; D053762:Interleukin-12 Subunit p40; D007891:Leishmania / Q000254:growth & development / Q000276:immunology*; D007896:Leishmaniasis / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology* / Q000469:parasitology; D051379:Mice; D008807:Mice, Inbred BALB C; D021122:Protein Subunits / Q000378:metabolism*
chemical_list: D053762:Interleukin-12 Subunit p40; D008070:Lipopolysaccharides; D021122:Protein Subunits; D018664:Interleukin-12