Apoptosis

Recent data regarding the photopheresis mechanism of action have suggested that extracorporeal photopheresis induces apoptosis in all cells in the treated buffy coat, including lymphocytes, granulocytes, and monocytes. These treated cells represent only a small portion of the body’s total number of circulating leukocytes.

When methoxsalen-treated apoptotic cells are returned to the patient and reenter the circulation, they accumulate in lymphoid organs. Here they encounter antigen-presenting cells (APCs), which play an important role in removing these apoptotic cells from circulation.