Extracorporeal photochemotherapy: evaluation of two techniques and use in connective tissue disorders

Extracorporeal photochemotherapy (ECP) consists of collection of mononuclear cells, their irradiation with UV-A light in the presence of a photoactivable molecule--8-methoxy-psoralen (8-MOP) being the most widely used--and their reinjection into a patient. Two technical approaches have been developed. The photopheresis procedure involves four steps: (i) 8-MOP is given to the patient orally, 2 h before collection of white blood cells; (ii) a discontinuous flow cell separator (UVAR, Therakos, West Chester, PA, U.S.A.) is used for cell collection. The final product (740 mL) has a hematocrit of 4.5 +/- 1.7%); (iii) irradiation, performed with the same UVAR apparatus, begins before all the cells are collected, and lasts for 180 min after collection; and (iv) after irradiation, the buffy-coat is reinjected into the patient. We developed a technique summarized as follows: (i) mononuclear cell collection is performed using the Spectra (Cobe, Denver, CO, U.S.A.) cell separator, which provides a highly enriched mononuclear cell concentrate (always > 90% purity), in a small volume < 150 mL, subsequently adjusted to 300 mL for irradiation. Hematocrit of the final product is always < 2%. (ii) Soluble 8-MOP is added to the mononuclear cell concentrate at a final concentration of 200 ng/mL. (iii) Mononuclear cell concentrate is transferred in an EVA plastic bag (Macopharma, Tourcoing, France) to ensure an efficient irradiation with a UV irradiator (Vilber Lourmat, Marne-la-Vallée, France). (iv) After irradiation at 2 J/cm2 (time < 20 min), the cells are reinfused into the patient. Experimental and clinical data suggest that ECP has potential applications in the treatment of connective tissue disorders, such as systemic sclerosis and rheumatoid arthritis. Although encouraging data have been obtained, further clinical trials are warranted to establish the role of this therapy in these indications.