Immune Tolerance

Antigen-presenting cells (APCs) express a set of receptors that specifically recognize apoptotic cell ligands. These receptors target the apoptotic cells for phagocytosis by APCs. A subset of these receptors on APCs have signaling capacity, which alters APC function, as described below.

The uptake of photopheresis-induced apoptotic cells by APCs can lead to a combination of the following:

• Decreased production of pro-inflammatory cytokines
• Increased production of anti-inflammatory cytokines
• Decreased ability to stimulate T effector cell function
• Generation of T regulatory cells

This is believed to result in immune tolerance. Treatment with extracorporeal photopheresis therefore has the potential to restore immune balance, which effectively dampens unwanted immune responses.