A new device to study ex-vivo the effects of extracorporeal photochemotherapy on the immune system

Extracorporeal photochemotherapy (ECP) is a medical procedure effective in the treatment of several different T-cell mediated diseases such as cutaneous T-cell lymphoma and Graft-versus-Host Disease. During ECP treatment the patient’s blood is processed by means of a cell separator to collect leukocytes (leukapheresis), mostly lymphocytes and monocytes, which are then incubated with the photoactive drug 8-methoxypsoralen (8-MOP), exposed to ultraviolet-A light (UV-A) and reinfused to the patient. It has been suggested that during ECP not only UV-A irradiation but also changes in the environmental condition may be relevant. Although ECP has been shown to have an in-vivo immunomodulatory effect, the mechanisms through which ECP exerts its effect remain elusive. One of the reasons for this incomplete knowledge is the absence of a reliable model for ECP. er to investigate the effect of ECP on the peripheral immune system, we developed a new device which mimics the complete ECP cycle including blood transit through the cell separator. Peripheral blood samples (50 ml) were obtained from volunteers and processed using a peristaltic pump. Peripheral blood mononuclear cells (PBMC) were then collected and treated with 8-MOP and UV-A under the same conditions used for the patients’ therapy. Using this strategy we investigated 8-MOP, UV-A and their combined effect on the production of the pro-inflammatory cytokines interferon-γ (IFN-γ), interleukine-2 (IL-2) and tumor necrosis factor-α (TNF-α) in PBMC with and without polyclonal stimulation. stly demonstrated that our device does not affect total red and white blood cell counts. After 8-MOP and UV-A irradiation a significant decrease was observed in both activated CD4+ and CD8+ T lymphocytes producing IFN-γ, IL-2 and TNF-α. Our findings are in line with those previously obtained in humans after complete ECP treatment, thus suggesting that our newly developed device is suitable for investigating the mechanism of action of ECP ex-vivo.