Inactivation of lymphocytes in blood products using riboflavin photochemical treatment with visible light.

Immunocompetent lymphocytes present in blood products are an important cause of immune reactions following blood transfusion such as transfusion-associated graft-versus-host disease (TA-GVHD). In this study the effects of riboflavin photochemical treatment (RPT) on lymphocyte proliferation and cytokine production in vitro were measured to establish whether RPT of blood products can be used to prevent immune reactions resulting from transfused lymphocytes. Lymphocytes and riboflavin were added together in medical PVC transparent bags and then exposed to visible light. Control lymphocytes were exposed to light in the absence of riboflavin. Lymphocytes exposed to riboflavin photochemical treatment (RPT-lymphocytes) and control lymphocytes were tested for the proliferative ability and the production of several cytokines upon stimulation with antigens. Upon stimulation by phytohemagglutinin (PHA) the proliferation of RPT-lymphocytes was inhibited. Using flow cytometry it was shown that RPT-lymphocytes were unable to enter the S-phase of the cell cycle following PHA stimulation. The level of cytokines present in the supernatant of RPT-lymphocytes after stimulation by antigens was significantly lower than those present in the corresponding supernatant of control lymphocytes. RPT with visible light inactivates lymphocytes, inhibits lymphocyte proliferation and the production of cytokines. It appears to be a promising method to prevent immune reactions such as TA-GVHD.