NCAM1 and neoplasm: As members of the innate immune system, empowered with major histocompatibility complex (MHC)-independent cytolytic capacity, unstimulated NK cells and γδ T cells were able to kill the CD56+ tumor cell lines NB4, SH-SY5Y, and U266 to a variable degree (Figure 3, left panels), while unstimulated CD56-enriched CD8 T cells only showed marginal killing.