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.