Covalent labeling of immune cells.

Inflammation is a common, fast, and innate response of the immune system to sterile or infectious tissue damage or autoimmune triggers. It aims at minimizing tissue destruction and maintaining organ function, hence is vital to life. Therefore, the immune system comprises the concerted action of a variety of different immune cells with specific tasks in the initiation, maintenance, and termination of inflammation. Visualizing their localization, trafficking, and interaction is of utmost importance to unravel the dynamics of inflammation in the living organism and requires tools for cell-specific labeling and imaging. Many concepts for covalent cell-type or protein-specific labeling have been developed, but only few have been implemented for labeling immune cells. Here, we review approaches that were already successful for fluorescent reporters and radioactive nuclides. We also provide a glimpse on emerging technologies that bear potential for immune cell labeling and imaging in vivo.