Lymphoseek (Technetium Tc 99m diethylenetriaminepentaacetic acid mannosyl dextran, [Tc 99m] DTPA Mannosyl Dextran) is a radiotracer that accumulates in lymphatic tissue by binding to a mannose binding protein that resides on the surface of dendritic cells and macrophages. Lymphoseek is a macromolecule consisting of multiple units of DTPA and mannose, each synthetically attached to a 10 kilodalton dextran backbone. The mannose acts as a substrate for the receptor, and the DTPA serves as a chelating agent for labeling with Tc 99m.