5-Aminolevulinic acid photodynamic therapy with and without Er:YAG laser for actinic keratosis: Changes in immune infiltration

Introduction: Ultraviolet light induced DNA damage, combined with immunosuppression and inflammation are involved in the pathogenesis of actinic keratosis. Photodynamic therapy not only destroys dysplastic cells via tissue destruction and vascular shutdown, but also induces an acute local inflammatory response and activates both the innate and adaptive immune system. In our current work we aimed to compare immunohistochemistry features of inflammatory infiltrate of actinic keratoses after 5-aminolevulinic acid photodynamic therapy with or without Er:YAG laser resurfacing. Methods: Eleven patients with multiple actinic keratosis on the scalp, face, hands or forearms were treated by conventional and Er:YAG laser assisted 5-aminolevulinic acid PDT in split-site manner. Biopsies of AKs were taken before, 48 h and 3 months after the treatment. CD3, CD4, CD8, CD1a, Ki67 and p53 expressions were analyzed by immunohistochemical methods. Results: The number of p53 and Ki67 positive cells decreased significantly 3 months after treatment, but the abnormal cells were not eliminated totally. The number of CD1a ⁺ Langerhans cells significantly decreased 48 h after both treatments, while CD8 ⁺ T cell count was significantly lower 3 months after Er:YAG laser assisted photodynamic therapy. However, the number of CD3 ⁺ and CD4 ⁺ T cells were not changed significantly 48 h and 3 months later. Conclusions: One session of 5-aminolevulinic acid photodynamic therapy even with Er:YAG laser pretreatment could not terminate actinic damage totally. Photodynamic therapy induced immunological changes. However further investigations are needed to answer how the composition of actinic keratosis’ immune infiltrate influence the effect of photodynamic therapy.