Impact of psoralen/UVA-treatment on survival, activation, and immunostimulatory capacity of monocyte-derived dendritic cells.
BACKGROUND
Extracorporeal Photopheresis (ECP) has been shown to be an effective treatment of graft-versus-host disease, solid organ graft rejection, and other T-cell-mediated diseases. The mechanisms of action of ECP include lymphocyte apoptosis, cytokine modulation, and the induction of regulatory T cells. It has been suggested that dendritic cells (DCs) are more resistant to ECP-induced apoptosis and might be directly modulated by ECP. We tested this hypothesis using in vitro Psoralen/UVA (PUVA) treatment as an in vitro model of ECP.


METHODS
Monocyte-derived DCs (mo-DCs) were treated with 8-methoxypsoralen /UVA and analyzed for surface molecule expression, apoptosis markers, endocytosis, and migratory and immunostimulatory capacity. Mo-DC phenotype and cytokine secretion was tested after CD40L stimulation. Naive T cells stimulated with PUVA-treated mo-DCs were tested for Th1/Th2 cytokine secretion and associated chemokine receptor patterns.


RESULTS
DCs underwent apoptosis after in vitro PUVA and in vivo ECP. In vitro, the induction of apoptosis was preceded by partial maturation of immature mo-DCs. PUVA-treated immature mo-DCs also exhibited enhanced migratory and immunostimulatory capacity. However, mo-DCs stimulation through CD40 ligation was abrogated and interleukin (IL)-12 secretion was abolished 24 hr after PUVA treatment. PUVA-treated mo-DCs skewed naive T cells toward a Th2 response as defined by increased IL-4, IL-10, and IL-13 and decreased interferon-gamma levels, and the expression of the Th2-associated chemokine receptors CCR4 and CCR10. The observed Th2 shift was partially reversed by exogenous IL-12.


CONCLUSIONS
These data suggest that direct modulation of DC function as well as apoptosis contribute to the immunoregulatory effects of ECP.
Holtick
Udo
U
Haematological Sciences, Institute of Cellular Medicine, Newcastle University, Newcastle-upon-Tyne, United Kingdom.
Marshall
Scott R
SR
Wang
Xiao-Nong
XN
Hilkens
Catharien M U
CM
Dickinson
Anne M
AM
D023201:CD40 Ligand / Q000187:drug effects / Q000502:physiology; D018929:Cell Culture Techniques / Q000379:methods; D002455:Cell Division / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000032:analysis; D003713:Dendritic Cells / Q000166:cytology* / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D004705:Endocytosis / Q000187:drug effects; D005434:Flow Cytometry; D011564:Furocoumarins / Q000494:pharmacology*; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects; D009000:Monocytes / Q000166:cytology / Q000276:immunology*; D014466:Ultraviolet Rays
D016207:Cytokines; D011564:Furocoumarins; D023201:CD40 Ligand