Inflammatory responses in the nervous system are very tightly regulated. In particular, T helper 1 type T cell responses must be kept in check, and a potent negative regulator of these cells is the surface receptor TIM3, a member of the T cell immunoglobulin and mucin family. However, Anderson et al. report the unexpected finding that TIM3 also promotes inflammation through expression on cells of the innate immune system--namely, dendritic cells and microglia of the brain. The opposing roles for the same immune protein when expressed on different populations of immune cells raise intriguing questions about the balance between the promotion and inhibition of tissue inflammation.
A. C. Anderson, D. E. Anderson, L. Bregoli, W. D. Hastings, N. Kassam, C. Lei, R. Chandwaskar, J. Karman, E. W. Su, M. Hirashima, J. N. Bruce, L. P. Kane, V. K. Kuchroo, D. A. Hafler, Promotion of tissue inflammation by the immune receptor Tim-3 expressed on innate immune cells. Science 318, 1141-1143 (2007). [Abstract] [Full Text]