T-Cell death, phosphatidylserine exposure and reduced proliferation rate to validate extracorporeal photochemotherapy

Background and Objectives Extracorporeal photochemotherapy (ECP) is an established therapy in various diseases, such as cutaneous T‐cell lymphoma and graft‐versus‐host disease. This study was performed to investigate the practicability of a flow cytometric T‐cell evaluation after ECP as a tool to validate the quality of ECP procedures and to enable the comparability of treatments with different ECP devices. Materials and Methods Peripheral blood mononuclear cells (PBMNCs) of healthy volunteer blood donors were treated by offline ECP. To quantify the effect of ECP on T cells in vitro, phosphatidylserine exposure and 7‐aminoactinomycin D (7‐AAD) reactivity as well as the proliferative activity of phytohaemagglutinin‐induced, viable CD3+ lymphocytes were analysed by flow cytometry. Results The expected T‐cell death after ECP was confirmed by 7‐AAD measurements. Phosphatidylserine exposure gradually increased between 20 and 70 h after ECP. Treatment‐related inhibition of T‐cell proliferation was 92·6 ± 1·4%. Conclusion The combination of viability, phosphatidylserine exposure and T‐cell division analyses by flow cytometry in a single‐platform system provides a valuable tool to validate ECP procedures.