Extracorporeal photochemotherapy

Abstract

Although extracorporeal photochemotherapy (ECP) is reported to be effective for a wide variety of diseases, such as cutaneous T cell lymphoma, autoimmune diseases, organ graft rejection, and graft versus host disease, its mechanism of action remains unclear. The basis of extracorporeal photopheresis is the reinfusion of leukocytes previously exposed to 8-methoxypsoralen (8-MOP) and ultraviolet A radiation. Although only 5-10% of circulating mononuclear cells is treated during one ECP procedure, the treatment has long-lasting immunomodulatory effects. The advantage of photopheresis treatment is the low frequency of side effects related to treatment. The disadvantages, however, are the practical efforts required and the high treatment cost. Recent studies demonstrated that ECP downregulates the immune response and induces tolerance by regulatory T cells. Other studies suggest that the mechanism of ECP also involves the recruitment and involvement of additional immune cells. Although immune tolerance induced by ECP is the most likely mechanism of the clinical efficacy of ECP it is not clear how ECP, both activates tumor immunity against cutaneous T-cell lymphoma and induces tolerance in autoreactive disorders. Further studies are necessary to determine the details of the underlying mechanisms of action.

Extracorporeal photopheresis as second‐line therapy for patients with acute graft‐versus‐host disease: does the number of cells treated matter?

“…Advantages of ECP include the low rates of infectious complications and virus reactivation compared with other treatment modalities, such as anti‐thymocyte globulin or monoclonal antibodies (e.g., basiliximab, etanercept, infliximab) . Although the exact mechanism of action has not yet been fully elucidated, it has been shown that ECP induces apoptosis in treated lymphocytes, especially in alloreactive T cells, which actively proliferate during GVHD, having a higher susceptibility to apoptosis than resting cells . In contrast to systemic immunosuppressants, ECP has immunomodulatory effects, including expansion of regulatory T cells, modulation of cytokine production, and maturation of dendritic cells …”

Response of steroid‐refractory chronic graft‐versus‐host disease to extracorporeal photopheresis correlates with the dose of CD3+ lymphocytes harvested during early treatment cycles

“…ECP involves the induction of apoptosis in treated lymphocytes; alloreactive T cells, which actively proliferate during GVHD, have higher susceptibility to apoptosis than resting lymphocytes . ECP, moreover, induces tolerogenic dendritic cells that stimulate a Th2 rather than Th1 response and, after the phagocytosis of apoptotic T cells, gives rise to a clonotypic immune reaction and leads to tolerance …”

Therapeutic potential of monocytic MDSCs from peripheral blood monocytes in transplant rejection

“…One such candidate is administration by pheresis. Among the various types of pheresis, extracorporeal photopheresis (ECP) is well known to have therapeutic potential in transplant rejections, especially in cases of cardiac transplant rejection [74] . ECP has been reported to affect peripheral blood monocytes, resulting in the induction of Treg and the development of immunological tolerance [75,76] .…”