Immunomodulatory effects of extracorporeal photochemotherapy in patients with extensive chronic graft-versus-host disease

Extracorporeal photochemotherapy (ECP) has been associated with clinical im provement in several patients with acute and chronic graft-versus-host dise ase (cGVHD) after allogeneic bone marrow transplantation, but the mechanism of action Is unknown. This study tested the hypothesis that in patients wi th cGVHD, ECP modulates alloreactivity by affecting activated lymphocyte po pulations or by altering the interaction between effector lymphocytes and a ntigen-presenting cells (APCs). Ten patients who had refractory cGVHD were treated with ECP, and the clinical response to and immunologic effects of t his therapy were assessed. Seven patients had a response and 3 had no chang e in clinical manifestations of cGVHD. One patient died tram catheter-relat ed sepsis. Immunologic effects observed after ECP included normalization of inverted ratios of CD4 to CD8 cells, an increase in the number of CD3-CD56 (+) natural killer (NK) cells, and a decrease in CD80(+) and CD123(+) circu lating dendritic cells. The results suggest that ECP modulates both NK cell s and APC populations in patients with cGVHD. (C) 2001 by The American Soci ety of Hematology.