Regulatory T cells and cancer.

Increasing evidence indicates that T regulatory (Treg) cells have the potent ability to suppress host immune responses, thus preventing autoimmune diseases. However, recent studies demonstrate that tumor cells can recruit these Treg cells to inhibit antitumor immunity in the tumor microenvironment, thus limiting the efficiency of cancer immunotherapy. Tumor-specific Treg cells have recently been identified and characterized, providing compelling evidence that such antigen-specific Treg cells can induce tumor-specific local immune tolerance. Vaccine strategies designed to overcome tumor-associated immune suppression are crucial to successful immunotherapy. Recent findings indicate that Toll-like receptors directly regulate the suppressive activity of human Treg cells, which might offer new opportunities to improve the outcome of cancer immunotherapy by co-administration of certain Toll-like receptor ligands and antigenic peptides.