IL21 and neoplasm: IL-21, which is produced by Th17 cells, can expand CD8+ T cells, leading to tumor regression in NSCLC and melanoma (25) Moreover, Th17 cells are found to promote protective antitumor immune responses by promoting effector T-cell, dendritic-cell (DC), and NK-cell tumor microenvironment (TME) recruitment and retention within the TME (50).