IL21 and neoplasm: Investigation of the molecular mechanisms of B16F10/GPI-IL-21 vaccine combined with the TGF-β1 knockdown in the B16F10 cells revealed that this combination caused the mice to develop a significant splenocyte cytotoxicity to the B16F10 cells or the YAC-1 cells; this suggested strong CTL and NK activities, whereas the CD4+CD25+Treg cells, which are a natural regulatory T cells with repressors of protective immunity and antitumor effectiveness, in splenocytes and tumor draining lymph nodes were obviously decreased.