This manuscript summarizes the content in the YouTube video ( https// ). A sensitive and specific imaging biomarker to monitor immune activation and quantify pharmacodynamic responses would be useful for development of immunomodulating anti-cancer agents. PF-07062119 is a T cell engaging bispecific antibody that binds to CD3 and guanylyl cyclase C, a protein that is over-expressed by colorectal cancers. Here, we used Zr-Df-IAB22M2C( Zr-Df-Crefmirlimab), a human CD8-specific minibody to monitor CD8+ T c