RESUMO
Dendritic cells (DCs) are a phenotypically and functionally heterogenous population of leukocytes with distinct subsets serving a different set of specialized immune functions. Here we applied an in vitro whole cell panning approach using antibody phage display technology to identify cell-surface epitopes specifically expressed on human blood BDCA3(+) DCs. A single-chain antibody fragment (anti-1F12 scFv) was isolated that recognizes a conserved surface antigen expressed on both human BDCA3(+) DCs and mouse CD8alpha(+) DCs. We demonstrate that anti-1F12 scFv binds Nectin-like protein 2 (Necl2, Tslc1, SynCaM, SgIGSF, or Igsf4), an adhesion molecule involved in tumor suppression, synapse formation, and spermatogenesis. Thus, Necl2 defines a specialized subset of DCs in both mouse and human. We further show that Necl2 binds Class-I-restricted T-cell-associated molecule (CRTAM), a receptor primarily expressed on activated cytotoxic lymphocytes. When present on antigen presenting cells, Necl2 regulates IL-22 expression by activated CD8(+) T-cells. We propose that Necl2/CRTAM molecular pair could regulate a large panel of cell/cell interactions both within and outside of the immune system.
Assuntos
Células Dendríticas/citologia , Imunoglobulinas/metabolismo , Imunoglobulinas/fisiologia , Proteínas de Membrana/fisiologia , Linfócitos T/metabolismo , Animais , Western Blotting , Linfócitos T CD8-Positivos/imunologia , Adesão Celular , Molécula 1 de Adesão Celular , Moléculas de Adesão Celular , Agregação Celular , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Separação Celular , Técnicas de Cocultura , Eletroforese em Gel de Poliacrilamida , Feminino , Citometria de Fluxo , Humanos , Sistema Imunitário/fisiologia , Immunoblotting , Imunoprecipitação , Interleucinas/biossíntese , Lentivirus/genética , Leucócitos/metabolismo , Ligantes , Linfócitos/citologia , Espectrometria de Massas , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Octoxinol/farmacologia , Biblioteca de Peptídeos , Fenótipo , Reação em Cadeia da Polimerase , Ligação Proteica , Estrutura Terciária de Proteína , RNA Mensageiro/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Baço/metabolismo , Interleucina 22RESUMO
CD123(bright) plasmacytoid cells (PC) and CD1c(+) peripheral blood myeloid dendritic cells (DC) are two human DC precursors that can be expanded in vivo by Fms-like tyrosine kinase 3 ligand (FL). It has been proposed that PC and myeloid CD1c(+) DC may represent two distinct lineages of DC. However, the phylogenetic affiliation of PC and its relationship with myeloid DC remain controversial. Here we show that CD123(bright)HLA-DR(+) PC from FL-treated healthy volunteers can be divided into mutually exclusive subsets that harbor either lymphoid or myeloid features. Lymphoid-like PC represent the majority of PC and include pTalpha-, CD3epsilon-, and CD7-expressing cells. They exhibit TCR-beta gene loci in germline configuration and show low allostimulatory capacity, but produce type I IFN upon virus infection and can be differentiated in vitro into potent APC. Myeloid-like PC represent a minor fraction of the total PC population. They exhibit a striking PC/myeloid DC intermediate phenotype (CD5(+)CD11c(low)CD45RA(low)CD45RO(-)CD101(+)), produce proinflammatory cytokines, and do not require in vitro maturation to act as potent APCs. We propose that, rather than forming a lineage, PC might represent a population of lymphoid cells undergoing an in vivo cell fate conversion from a lymphoid to a myeloid cell type.
