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GVHD reversed by extracorporeal photopheresis-treated cells (ECP)
Last Updated: 2008-09-05
NEW YORK (Reuters Health) -
Cells treated with extracorporeal photopheresis (ECP) can reverse graft-versus-host disease (GVHD) by increasing donor regulatory T cells and by indirectly reducing the number of donor effector lymphocytes that have not undergone ECP, according to the findings of a study that used two well-established mouse models.
In ECP, isolated white blood cells are exposed to 8-methoxypsoralen (8-MOP) and ultraviolet-A light, the researchers explain in the August 15 issue of Blood. Although 8-MOP is normally biologically inert, in the presence of UVA light, it cross-links DNA and causes apoptosis. Although ECP is used to treat cutaneous T-cell lymphoma and immune-mediated diseases, its effects on the immune system beyond apoptosis are largely unknown.
Bone marrow transplantation (BMT), a common cause of GVHD in humans, was used to induce GVHD in mice. In both of the mouse models of GVHD, bone marrow donor and host were identical at the major histocompatibility complex. The models differed by whether the disease was mediated by CD8+ or CD4+ T cells.
A single injection of ECP-treated cells suppressed GVHD and 4 weekly injections improved both survival and GVHD clinical scores, compared with controls injected with either untreated cells or diluent. Mice receiving ECP-treated cells also showed significantly less histopathological damage in all three GVHD target organs (liver, gut and skin) and dramatically improved immune reconstitution 8 weeks after BMT.