Abstract
Tumor antigen–specific T-cell tolerance imposes a significant barrier to the development of effective therapeutic cancer vaccines. Bone marrow–derived antigen-presenting cells (APCs) are critical in the induction of this unresponsive state. Here we show that in vitro treatment of APCs with the tyrosine kinase inhibitor, imatinib mesylate (STI-571), enhances the activation of naive antigen-specific T cells and restores the responsiveness of tolerant T cells from tumor-bearing hosts. Furthermore, in vivo treatment with STI-571 not only prevented the induction of tolerance in tumor-specific CD4+ T cells, preserving their responsiveness to a subsequent immunization, but also resulted in enhanced vaccine efficacy. These findings demonstrate that tolerance to tumor antigens is not an insurmountable obstacle and points to modulation of APC function as a promising strategy in the immunotherapy of cancer.
Deficiency in NOD Antigen-Presenting Cell Function May Be Responsible for Suboptimal CD4+CD25+ T-Cell-Mediated Regulation and Type 1 Diabetes Development in NOD Mice