// Mikako Ogawa 1, 7, * , Yusuke Tomita 2, * , Yuko Nakamura 3 , Min-Jung Lee 2 , Sunmin Lee 2 , Saori Tomita 2 , Tadanobu Nagaya 3 , Kazuhide Sato 3 , Toyohiko Yamauchi 4 , Hidenao Iwai 4 , Abhishek Kumar 5 , Timothy Haystead 6 , Hari Shroff 5 , Peter L. Choyke 3 , Jane B. Trepel 2 , Hisataka Kobayashi 3 1 Medical Photonics Research Center, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan 2 Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA 3 Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA 4 Central Research Laboratory, Hamamatsu Photonics K. K., Hamamatsu 434-8601, Japan 5 Section on High Resolution Optical Imaging, NIBIB/NIH, Bethesda, MD 20892, USA 6 Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27710, USA 7 Laboratory for Bioanalysis and Molecular Imaging, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan * Co-first author Correspondence to: Hisataka Kobayashi, email: Kobayash@mail.nih.gov Keywords: near infrared photoimmunotherapy, immunogenic cell death Received: October 12, 2016 Accepted: December 13, 2016 Published: January 02, 2017 ABSTRACT Immunogenic cell death (ICD) is a form of cell death that activates an adaptive immune response against dead-cell-associated antigens. Cancer cells killed via ICD can elicit antitumor immunity. ICD is efficiently induced by near-infrared photo-immunotherapy (NIR-PIT) that selectively kills target-cells on which antibody-photoabsorber conjugates bind and are activated by NIR light exposure. Advanced live cell microscopies showed that NIR-PIT caused rapid and irreversible damage to the cell membrane function leading to swelling and bursting, releasing intracellular components due to the influx of water into the cell. The process also induces relocation of ICD bio markers including calreticulin, Hsp70 and Hsp90 to the cell surface and the rapid release of immunogenic signals including ATP and HMGB1 followed by maturation of immature dendritic cells. Thus, NIR-PIT is a therapy that kills tumor cells by ICD, eliciting a host immune response against tumor.