Photopheresis: Clinical applications and mechanism of action

Photopheresis is a leukapheresis-based therapy that utilizes 8-methoxypsora len and ultraviolet A irradiation. Photopheresis is currently available at approximately 150 medical centers worldwide, Recent evidence suggests that this therapy used as a single agent may significantly prolong life, as well as induce a 50%-75% response rate among individuals with advanced cutaneou s T cell lymphoma (CTCL), Furthermore, a 20%-25% complete response rate wit h photopheresis alone, or in combination with other biologic response modif iers, has been obtained at our institution among patients with Sezary syndr ome. These complete responses have been characterized by the complete disap pearance of morphologically atypical cells from the skin and blood. The use of sensitive molecular techniques has also confirmed the sustained disappe arance of the malignant T cell clone from the blood of patients with comple te responses. In addition to the treatment of CTCL, numerous reports indica te that photopheresis is a potent agent in the therapy of acute allograft r ejection among cardiac, lung, and renal transplant recipients. Chronic graf t versus host disease also appears to be quite responsive to photopheresis therapy. Likewise, there may also be a potential role for photopheresis in the therapy of certain autoimmune diseases that are poorly responsive to co nventional therapy. The immunologic basis for the responses of patients wit h these conditions is Likely due to the induction of anticlonotypic immunit y directed against pathogenic clones of T lymphocytes, Treatment-induced ap optotic death of pathogenic T cells and activation of antigen presenting ce lls are postulated to have important effects in this therapeutic process.