The influence of photodynamic therapy on the immune response

Summary 

Photodynamic therapy (PDT) is a clinically approved therapeutic modality used for the management of several types of tumors as well as non-malignant diseases. Most of the effects of this treatment regimen result from direct action of singlet oxygen and reactive oxygen species. However, accumulating evidence indicates that antitumor effects are also mediated by indirect stimulation of inflammatory and immune responses. These responses include rapid local infiltration of tumors by neutrophils and macrophages accompanied by systemic release of inflammatory mediators. This early response can initiate and translate into a more precise immune reaction that involves activation of specific T lymphocytes that seem to be necessary for the ultimate control of residual tumor cells. Although still incompletely understood, PDT can not only activate but also suppress the immune response depending on several variables. This review summarizes the influence of PDT on the immune response and discusses its importance in the management of human diseases.

Abbreviations: 8-MOP, 8-methoxypsoralen, BCG, Bacillus Calmette-Guerin, ALA, 5-aminolevulinic acid, CD, cluster of differentiation, CHS, contact hypersensitivity, DBPMAF, Vitamin D₃-binding protein-derived macrophage-activating factor, DC, dendritic cells, EAE, experimental autoimmune encephalomyelitis, ECP, extracorporeal photochemotherapy, G-CSF, granulocyte colony-stimulating factor, GM-CSF, granulocyte-macrophages colony-stimulating factor, GVHD, graft-versus-host disease, GVL, graft versus leukemia, HLA, human leukocyte antigen, HSP, heat shock protein, IFN, interferon, KC, keratinocytes-derived chemokines, MAC, membrane attack complex, MHC, major histocompatibility complex, MIP, macrophage inflammatory protein, MPO, myeloperoxidase, MS, multiple sclerosis, NK, natural killer, NO, nitric oxide, PDT, photodynamic therapy, PIT, photoimmunotherapy, SOD, superoxide dismutase, TAA, tumor-associated antigen, TGF-β, transforming growth factor-β, TLR, Toll-like receptor, TNF, tumor necrosis factor, TRAIL, TNF-related apoptosis-inducing ligand, UVA, ultraviolet A

Keywords: Photodynamic therapy, Tumor, Immune response, Inflammation, Dendritic cells