Elucidating the Role of Host Tim-1 in Anti-tumour Immunity
Abstract
T cell immunoglobulin and mucin domain-1 (Tim-1) is expressed by CD4+ T cells, invariant natural killer T (iNKT) cells, and regulatory B cells (Bregs). Tim-1 expression on CD4+ T cells and iNKT cells typically promote proinflammatory responses, while Tim-1-expressing Bregs are immunosuppressive. However, the potential role of Tim-1 in anti-tumour immunity is unclear. To investigate the effects of Tim-1 on B16F1 melanoma and MC38 colorectal adenocarcinoma models, I compared tumour growth and survival between Tim-1-expressing (wild-type) and Tim-1-deficient mice. Using B16F1 melanoma, I demonstrated that Tim-1-deficient mice exhibited delayed tumour growth and improved survival, compared to wild-type mice. When immunized with heat-killed B16F1 melanoma cells, decreased frequencies of Bregs were found in Tim-1-deficient mice. These data suggest that Tim-1 expression may promote tumour growth by inducing Bregs. Therefore, anti-cancer treatments aimed at suppressing the function of Tim-1-expressing Bregs may be of therapeutic value.