Extracorporeal photochemotherapy is accompanied by increasing levels of circulating CD4+CD25+GITR+Foxp3+CD62L+ functional regulatory T-cells in patients with graft-versus-host disease

BACKGROUND. Extracorporeal photochemotherapy (ECP) produces clinical improvements in refractory/resistant graft-versus-host disease (GvHD). Immunological mechanisms of ECP are still under investigation. METHODS. We have evaluated the changes in frequency and immunophenotype of circulating regulatory T cells (T-regs) in 10 patients undergoing allogeneic hematopoietic stem cell transplantation, receiving ECP for acute (n=4) or chronic (n=6) GvHD. T-regs were monitored for expression of surface CD4, CD25, GITR, CD45RO, CD62L and intracytoplasmic Foxp3. T-regs were sorted by fluorescence-activated cell sorting to perform functional assays by interferon (IFN)-γ enzyme-linked immunospot and real-time quantitative polymerase chain reaction (RQ-PCR) to measure Foxp3, transforming growth factor (TGF)-β, and interleukin (IL)-10 mRNA. RESULTS. ECP was accompanied by a significant increase of CD4+CD25+ T-regs after six procedures, increasing from 8.9% to 29.1% of total CD4 (P