Cutaneous T cell lymphoma and graft-versus-host disease: A comparison of in vivo effects of extracorporeal photochemotherapy on Foxp3+ regulatory T cells

Extracorporeal photochemotherapy (ECP) is a well established treatment for both cutaneous T cell lymphoma (CTCL) and graft-versus-host disease (GVHD). However, the general effector mechanism is not fully settled. Twenty-four patients with CTCL and 14 patients with GVHD were included to assess the relative numbers of regulatory T cells (Treg) and any change in the serum cytokine profile during 6 months of ECP therapy. The relative amount of Treg cells was twice as high in CTCL compared to GVHD and healthy controls. TGF-β was on average three times higher in GVHD than in CTCL. Both patient groups had a small but significant increase in TGF-β after treatment. Our results indicate a strengthened Treg function as a result of ECP. Elevated TGF-β may indicate high Treg activation in GVHD, whereas an increased number of Treg cells in CTCL could be interpreted as a response that is involved in down-regulating the lymphoma cells.