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

Academic Article


  • 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 Pc4, 110 J cm 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. © 2008 The Authors. + + -/- -1 -2 -/- + -/- -/- -/- -/-
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    Digital Object Identifier (doi)

    Author List

  • Yusuf N; Katiyar SK; Elmets CA
  • Start Page

  • 366
  • End Page

  • 370
  • Volume

  • 84
  • Issue

  • 2