The secretion of immunosuppressive factors like interleukin-10 (IL-10), either by tumor cells or by tumor-infiltrating leukocytes, has been recognized as one of the mechanisms involved in tumor immunological escape and a serious obstacle for successful immunotherapy. Therefore, any therapeutic attempts aimed at inducing antitumor immunity in tumor-bearing hosts must overcome this immunosuppressive state. This study aimed to determine whether dendritic cell (DC) immunization, a promising approach to induce antitumor immunity, could break IL-10-induced anergic state in CD4(+) T cells, essential cells in generating tumor-specific immunity. We found that the ability of DC to reverse IL-10-induced anergic state in human CD4(+) T cells is dependent on the IL-10 concentration that T cells have been exposed to and the degree of DC maturation. The efficacy of mature DC in reversing T cell anergy can be mimicked by higher cell numbers of immature DC. In addition, activated T cells induced by DC stimulation are sensitive to IL-10 treatment. Collectively, our results, suggest the use of mature DC and the necessity of antagonizing the action of tumor-derived IL-10 in immunotherapy of cancer with DC immunization. (C) 2001 Elsevier Science B.V. All rights reserved.
