CD366 also known as TIM-3 (T-cell immunoglobulin and mucin containing protein-3) is a type I transmembrane protein that in humans is encoded by the HAVCR2 gene. TIM-3 is expressed on activated human CD4+ T cells and regulates Th1 and Th17 cytokines. TIM-3 acts as a negative regulator of Th1/Tc1 function by triggering cell death upon interaction with its ligand, galectin-9. TIM-3 is also known to be expressed on certain innate immune cells, including NK cells, macrophages, DCs, and mast cells. TIM-3 plays an important role in immunity, the dysregulation of TIM-3 expression has been associated with autoimmune diseases, viral infections and cancer and it’s expression on numerous cell types (T cell, Treg, dendritic cell, myeloid cells) favors tumor escape to immune cells.