Fredric S. Young, PhD
To the Editors: I read with great interest the article on extracorporeal photopheresis in a recent issue (1). As pointed out in the article, it is not known how this therapy stimulates the immune system. Although it came from the field of photodynamic cancer therapy, it is possible, and perhaps even likely, that the immune system stimulation results from mechanisms unrelated to the photoactivation of the psoralen compounds. In the 1930s and 1940s, the Knott technique, an extracorporeal irradiation of blood with ultraviolet light, was widely reported to be effective in the therapy of viral infections (2). Further, a new
Young FS. "Jump Starting" the Immune System. Ann Intern Med. 1990;113:995. doi: 10.7326/0003-4819-113-12-995_1
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Published: Ann Intern Med. 1990;113(12):995.
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