title: 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.
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.
authors.affiliation: Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: Nabiha
authors.initials: N
authors.lastname: Yusuf
authors.forename: Santosh K
authors.initials: SK
authors.lastname: Katiyar
authors.forename: Craig A
authors.initials: CA
authors.lastname: Elmets
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D005260:Female; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology*; D054833:Isoindoles; D051379:Mice; D008809:Mice, Inbred C3H; D010778:Photochemotherapy
chemical_list: D007166:Immunosuppressive Agents; D007211:Indoles; D054833:Isoindoles; C013647:phthalocyanine