title: In vitro treatment of monocytes with 8-methoxypsolaren and ultraviolet A light induces dendritic cells with a tolerogenic phenotype.
abstract: Extracorporeal photopheresis (ECP) has been considered an efficient dendritic cell (DC) therapy, used for treating both T cell malignancy, as well as T cell-mediated diseases. During the ECP procedure leucocytes are exposed to photoactivable agent 8-methoxypsolaren (8-MOP) and ultraviolet (UV) A radiation (PUVA) prior to reinfusion. Despite its clinical efficacy the mechanism of action remains elusive. As it has been reported that ECP might promote the differentiation of monocytes into immature DCs, we investigated the effects of UVA light (2 J/cm(2)) and 8-MOP (100 ng/ml) on in vitro monocyte-to-DC differentiation from normal donors. DCs were generated from human purified CD14(+) cells. Because monocytes are killed by PUVA and taking into account that only 5-10% of circulating mononuclear cells are exposed to PUVA during the ECP procedure, we developed an assay in which 10% of PUVA-treated monocytes were co-cultured with untreated monocytes. We first demonstrate that the presence of 10% apoptotic cells and monocyte activation were not enough to induce monocyte differentiation into DCs. Adding cytokines to our culture system, we obtained immature DCs characterized by significantly higher phagocytic activity and human leucocyte antigen D-related (HLA-DR) expression. These DCs preserved the capacity to be activated by lipopolysaccharide, but showed a reduced capacity to induce allogeneic T cell proliferation when first co-cultured with 10% of PUVA-treated cells. Our experimental design provides a novel insight into the real action of 8-MOP and UVA light on dendritic cell biology, suggesting an additional mechanism by which 8-MOP and UVA light exposure may influence immune responses.
authors: Department of Reproductive Medicine and Pediatrics, Laboratory of Immunology, University of Pisa, Pisa, Italy.
authors: A
authors: A
authors: Legitimo
authors: R
authors: R
authors: Consolini
authors: A
authors: A
authors: Failli
authors: S
authors: S
authors: Fabiano
authors: W
authors: W
authors: Bencivelli
authors: F
authors: F
authors: Scatena
authors: F
authors: F
authors: Mosca
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002454:Cell Differentiation / Q000187:drug effects / Q000528:radiation effects; D018920:Coculture Techniques; D016207:Cytokines / Q000276:immunology; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects*; D006801:Humans; D007108:Immune Tolerance; D016130:Immunophenotyping; D008213:Lymphocyte Activation / Q000276:immunology; D007959:Lymphocyte Culture Test, Mixed; D008730:Methoxsalen / Q000494:pharmacology*; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects*; D010587:Phagocytosis / Q000187:drug effects / Q000528:radiation effects; D017893:Photopheresis; D017319:Photosensitizing Agents / Q000494:pharmacology*; D014466:Ultraviolet Rays
chemical_list: D016207:Cytokines; D017319:Photosensitizing Agents; D008730:Methoxsalen