Extracorporeal photopheresis differentially regulates the expression of phosphorylated STAT-1 and STAT-5 in treated monocytes and T cells, respectively.
BACKGROUND
Extracorporeal photopheresis (ECP) is effective in conditions with opposing immune etiology. ECP induces an immunomodulatory response through simultaneous monocyte activation and apoptosis induction of lymphocytes. However, ECP is also immunosuppressive, downregulating proinflammatory cytokines. Signal transducers and activators of transcription (STATs) are important mediators of cell-signaling systems, including cytokines. Ultraviolet (UV) immunosuppression is linked to reductions in cytokine-induced STAT phosphorylation.


OBJECTIVE
The aim of this study was to find whether ECP downregulates STAT phosphorylation.


METHODS
Pre- and post-ECP mononuclear cells from cutaneous T-cell lymphoma and chronic graft-versus-host disease patients were stimulated with either IFNbeta, IL2, or IL15. The percentage of IFNbeta-stimulated monocytes positive for phosphorylated STAT-1 (pSTAT-1) and the number of IL2- and IL15-stimulated T cells expressing phosphorylated STAT-5 (pSTAT-5) were determined at 0 and 24 h.


RESULTS
Post-ECP, pSTAT-1 levels in monocytes remained unchanged; however, at 24 h post-ECP the number of T cells expressing pSTAT-5 was reduced.


CONCLUSIONS
Following ECP, monocytes retain their ability to phosphorylate STAT-1, while pSTAT-5 expression is lost in lymphocytes. This differential effect of ECP may account for the diverse population of diseases that benefit.
Bladon
John
J
Department of Haematology, Rotherham General Hospital, S60 2UD, South Yorkshire, United Kingdom. john.bladon@rothgen.nhs.uk
Taylor
Peter
P
D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000378:metabolism; D006801:Humans; D008894:Milk Proteins / Q000096:biosynthesis* / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism* / Q000528:radiation effects*; D010766:Phosphorylation; D017893:Photopheresis; D050794:STAT1 Transcription Factor; D050799:STAT5 Transcription Factor; D013601:T-Lymphocytes / Q000378:metabolism* / Q000528:radiation effects*; D015534:Trans-Activators / Q000096:biosynthesis* / Q000378:metabolism
D004268:DNA-Binding Proteins; D008894:Milk Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050799:STAT5 Transcription Factor; D015534:Trans-Activators