Human invariant natural killer T cells: implications for immunotherapy

Human invariant natural killer T cells are a unique lymphocyte population that have an invariant T-cell receptor and recognize glycolipids instead of peptides in the restriction of CD1d molecules. These natural killer T cells play important roles in anti-tumor immunity, transplantation immunity, allergy, autoimmunity and microbial immunity. Since human natural killer T cells show high-level biological activity such as cytokine production, an anti-tumor effect and regulatory T-cell control, they may be a useful tool in immune-cell therapy. In this review, we summarize the immune responses mediated by human natural killer T cells, especially in tumor and transplantation immunity, and discuss their potential in clinical applications.