IL15 and neoplasm: Previously, we demonstrated that incubation of NK, but not T cells, with peptide-free recombinant Hsp70 protein in combination with pro-inflammatory cytokines, such as IL-2 or Il-15 can stimulate the cytotoxic, proliferative, and migratory capacity of NK cells against highly aggressive, mHsp70-positive tumor cells, in vitro (14, 23).