The immunosuppressive effects of phthalocyanine photodynamic therapy in mice are mediated by CD4+ and CD8+ T cells and can be adoptively transferred to naive recipients.
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| Abstract |
Photodynamic therapy (PDT) is a promising treatment modality for malignant tumors but it is also immunosuppressive which may reduce its therapeutic efficacy. The purpose of our study was to elucidate the role of CD4+ and CD8+ T cells in PDT immunosuppression. Using silicon phthalocyanine 4 (Pc4) as photosensitizer, nontumor-bearing CD4 knockout (CD4-/-) mice and their wild type (WT) counterparts were subjected to Pc4-PDT in a manner identical to that used for tumor regression (1 cm spot size, 0.5 mg kg(-1) Pc4, 110 J cm(-2) light) to assess the effect of Pc4-PDT on cell-mediated immunity. There was a decrease in immunosuppression in CD4-/- mice compared with WT mice. We next examined the role of CD8+ T cells in Pc4-PDT-induced immunosuppression using CD8-/- mice following the same treatment regimen used for CD4-/- mice. Similar to CD4-/- mice, CD8-/- mice exhibited less immunosuppression than WT mice. Pc4-PDT-induced immunosuppression could be adoptively transferred with spleen cells from Pc4-PDT treated donor mice to syngenic naive recipients (P < 0.05) and was mediated primarily by T cells, although macrophages were also found to play a role. Procedures that limit PDT-induced immunosuppression but do not affect PDT-induced regression of tumors may prove superior to PDT alone in promoting long-term antitumor responses.
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| Authors | Nabiha Yusuf, Santosh K Katiyar, Craig A Elmets |
| Journal | Photochemistry and photobiology (Photochem Photobiol) 2008 Mar-Apr Vol. 84 Issue 2 Pg. 366-70 ISSN: 0031-8655 [Print] United States |
| PMID | 18208456 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, Non-P.H.S.) |
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