Kazuki (Kaz) Nagashima grew up in Tokyo, Japan. His childhood experience with food allergies drove his interest in the gut immune system and motivated him to go to medical school at the University of Tokyo, where he was inspired by a Clostridium difficile infection caused by dysbiosis of the microbiota.  He was fascinated by the mysterious intestinal ecosystem in which the immune system permits diet and microbiome and eliminates pathogens.

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To learn immunology research, he did his Ph.D. in the Hiroshi Takayanagi Lab at the University of Tokyo. He addressed a longstanding question in the host-microbe interaction – how antigens of the microbiome are recognized by the host's immune system and initiate an IgA response. He discovered a previously uncharacterized mesenchymal cell subset that induces epithelial microfold (M) cells and promotes the antigen-specific IgA response.

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To explore the host-microbiome interaction from a microbial perspective, he joined the Michael Fischbach Lab at Stanford University as a postdoc, where he developed a new technology to understand the high-resolution view of immune modulation by the gut microbiome.

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In 2024, he joined the Department of Molecular and Cellular Biology at Harvard University as an Assistant Professor. The Nagashima Lab aims to understand human immunology, microbiome, and diet at the level of molecular mechanisms.