We speculate that IL-21 exerts its influence in our culture system both at the antigen-presentation stage (as MHCI- and, to a lesser extent, MHC II-restricted antigen presentation by tumor cells occurs while tumor fragments are cultured ex vivo) (Gagnon et al., 2008) and at the expansion stage, where IL-21 selectively promotes the expansion of non-Treg populations. Here, IL21 is linked to neoplasm.