Extracorporeal photochemotherapy: early ex-vivo experience on healthy controls and a multiple sclerosis patient to investigate a new potential cell therapy.

Extracorporeal photochemotherapy (ECP) is a cell based procedure effective in the treatment of 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 which are then added with the photoactive drug 8-methoxypsoralen (8-MOP), exposed to ultraviolet-A light (UV-A) and reinfused into the patient. Even if the mechanisms of action of ECP remain elusive, it has been shown to own in-vivo immunomodulatory effects and to be effective also on experimental allergic encephalomyelitis (EAE) animals and in a small pilot study on multiple sclerosis (MS) patients. It has been suggested that during ECP not only UV-A irradiation but also changes in the environmental condition may be relevant. Therefore, we developed a new peristaltic-based bench device which reliably mimics ex-vivo the complete ECP cycle using 50 ml peripheral blood sample. Peripheral blood mononuclear cells (PBMC) were then collected and treated with 8-MOP and/or UV-A under the same conditions used for the patients’ therapy. Using this strategy we investigated 8-MOP and/or UV-A effect on the production of the inflammatory cytokines IFN-γ, IL-2 and TNF-α in PBMC after polyclonal stimulation. We observed a significant decrease in activated CD4+ and CD8+ T-lymphocytes producing cytokines after UV-A irradiation and a further decrease in the presence of 8-MOP. The decrease in cytokines production seemed to be both cytokine- and cell type-related. In fact TNF-α production was reduced to a lesser extent than IFN-γ and IL-2 ones, while CD4+ T-cells seemed to be more sensitive than CD8+ lymphocytes when IFN-gamma and IL-2 production was considered. Both T-cell population showed similar behaviour when TNF-α production was evaluated. Following this preliminary experience, this ex-vivo protocol will be used to deeply investigate the effect of ECP on EAE rats.