Initial study of the role of native interleukin-15 in generating tumor-specific cytotoxic T lymphocytes in a dendritic cell-mediated ex vivo system.

摘要

Adoptive cell transfer (ACT) immunotherapy using ex vivo expanded tumor-specific cytotoxic T lymphocytes (CTLs) is one of the most promising approaches for treating cancers. The quality and quantity of tumor-specific CTLs generated in vitro, which is believed to be mainly dependent on the dendritic cells (DCs) and the application of appropriate cytokines, may closely affect the efficiency of ACT. In this project, we have developed anti-IL15 monoclonal antibodies and a detection kit for IL-15. We have identified a signal peptide that can effectively export IL-15 mature protein from the transfected mammalian cells, and have obtained several clones secreting high levels of IL-15. Using this ex vivo priming system, we found that T cells primed in the presence of mammalian cell-expressed IL-15 had a higher frequency of viable cells, and were more resistant to activation-induced cell death. Intriguingly, the percentage of CD4+CD25 + T cells in the IL-15 treated group was much higher than the IL-2 treated group, while the percentage of CD4+CD25+Foxp3 + regulatory T cells was significantly lower in the IL-15 treated group. In addition, T cells primed in the presence of IL-15 exhibited phenotypes of effector memory T cells. However, there were no significant differences in the total number of T cells, frequency of tumor-specific CD8+IFN-gamma + T cells, nor the specific lysis of target cells between the IL-15 and IL-2 treated groups. We also found that d4 immature DCs generated with granulocyte/macrophage colony-stimulating factor (GM-CSF) and IL-15 had higher intensities of surface markers than traditional DCs generated with GM-CSF and IL-4, while the d6 mature DCs generated in both methods had similar surface markers. Collectively, these data may provide valuable information for the generation of high quantity and quality tumor-specific CTLs for ACT treatment of cancer.