Photochemical inactivation of lymphocytes by riboflavin with visible light for TA-GVHD prevention

Transfusion-associated graft-versus-host disease (TA-GVHD) is a life-threatening complication caused by the input of a number of immunocompetent allogeneic lymphocytes. This study focus on the photochemical effects of riboflavin excited by visible light (RB + L) treatment on human lymphocytes, to study the feasibility of using RB + L treatment to prevent adverse immune reactions caused by transfused lymphocytes. 100 μM riboflavin was added to lymphocyte suspensions. After exposure to 400-580 nm visible light with a total energy of 40 J/mL, cells were cultured and the ability of proliferation and cytokine secretion were assayed upon stimuli. Meanwhile, lymphocytes were also treated by gamma-irradiation as parallel to testify the inactivation effect of RB + L. Results showed that γ-irradiation and RB + L treated cells showed a decline in cell viability. After stimulation of phytohemagglutinin (PHA) or anti-CD3 together with anti-CD28, proliferative ability of RB + L treated cells was strongly inhibited when compared to untreated cells. The inhibitive rates of proliferation in RB + L group were also higher than those of cells treated by γ-irradiation. Results of CFSE assays also illustrated hardly any cell division of RB + L and γ-irradiation treated lymphocytes. Besides low level productions of IL-4 and IL-12, cytokine production of TNF-α, IFN-γ and IL-10 by incubation with PHA or IL-1β, IL-2, IL-6, IL-8, IL-10, TNF-α and IFN-γ stimulated by anti-CD3 plus anti-CD28 were suppressed after treatment of RB + L significantly. It was suggested that RB + L/γ-irradiation treatment induced cell apoptosis. These results indicated that RB + L treatment functionally inactivated lymphocytes by inhibiting cell proliferation and cytokine production. RB + L might be an alternative for TA-GVHD prevention.