Reginato, EMroz, PChung, HKawakubo, MWolf, PHamblin, Michael2014-11-032013Reginato, E, P Mroz, H Chung, M Kawakubo, P Wolf, and M R Hamblin. 2013. “Photodynamic therapy plus regulatory T-cell depletion produces immunity against a mouse tumour that expresses a self-antigen.” British Journal of Cancer 109 (8): 2167-2174. doi:10.1038/bjc.2013.580. http://dx.doi.org/10.1038/bjc.2013.580.0007-0920http://nrs.harvard.edu/urn-3:HUL.InstRepos:13347643Background: Photodynamic therapy (PDT) can lead to development of antigen-specific immune response and PDT-mediated immunity can be potentiated by T regulatory cell (Treg) depletion. We investigated whether the combination of PDT with cyclophosphamide (CY) could foster immunity against wild-type tumours expressing self-antigen (gp70). Methods: Mice with CT26 tumours were treated with PDT alone or in combination with low-dose CY. T regulatory cell numbers and transforming growth factor-β (TGF-β) levels were measured at several time points after treatment. Mice cured by PDT+CY were rechallenged with CT26 and monitored for long-term survival. Results: Photodynamic therapy+CY led to complete tumour regression and long-term survival in 90% of treated mice while the absolute numbers of Treg decreased after PDT+CY and the TGF-β levels were reduced to a level comparable to naïve mice. Sixty-five percent of the mice treated with PDT+CY that survived over 90 days tumour free rejected the rechallenge with the same tumour when a second dose of CY was administered before rechallenge but not without. Conclusion: Administration of CY before PDT led to depletion of Treg and potentiated PDT-mediated immunity, leading to long-term survival and development of memory immunity that was only uncovered by second Treg depletion.en-USphotodynamic therapyregulatory T cellsTGFCT26 tumouranti-tumour immunityJournal Article2014-11-0310.1038/bjc.2013.580