Tim-3, a negative regulator of anti-tumor immunity.

T cell immunoglobulin-3 (Tim-3) was identified nearly 10 years ago as a negative regulator of IFN-γ-secreting CD4(+) T helper 1 and CD8(+) T cytotoxic 1 cells. Tim-3 is now classed with other inhibitory receptors, such as cytotoxic lymphocyte antigen-4 and programmed death-1 that are commonly referred to as immune checkpoint molecules. Recent studies have highlighted Tim-3 as an important player in the CD8(+) T cell exhaustion that takes place in chronic immune conditions such as chronic viral infection and cancer in both humans and experimental models. In addition to its role in exhausted T cells, recent data suggest that Tim-3 can further influence cancer outcome through its action on myeloid cells and cancer stem cells.