Medical Definition of photopheresis
: an immunomodulating therapy used especially to treat cutaneous T-cell lymphomas that involves treating blood with a photoactive drug (as methoxsalen), obtaining a fraction rich in white blood cells, exposing the fraction to damaging ultraviolet radiation, and returning it to the body where it stimulates a therapeutic immunological response
Seen and Heard
What made you want to look up photopheresis? Please tell us where you read or heard it (including the quote, if possible).