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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 †
Author(s) -
Yusuf Nabiha,
Katiyar Santosh K.,
Elmets Craig A.
Publication year - 2008
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2007.00270.x
Subject(s) - immunosuppression , photodynamic therapy , cd8 , cytotoxic t cell , immunosurveillance , cancer research , immunology , immune system , syngenic , medicine , biology , chemistry , in vitro , biochemistry , organic chemistry
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.