Role of natural killer cells in bladder tumor

The role of natural killer (NK) cells in bladder tumors was assessed from the aspect of local and systemic immune responses. The NK cell activity was measured in a 4-hour 51Cr-release assay. The NK activity in patients with bladder tumor was lower, though not significantly, than that in normal individuals. In patients with bladder tumor, the NK activity was significantly lower in invasive tumors and lymph node metastases. Moreover, the NK activity was lower in those who died (n = 4) than it was in survivors (n = 21). In an in vitro experiment, OK432 significantly augmented the NK activity in peripheral blood lymphocytes (PBL), however, this augmentation was not always OK432 dose-dependent. The augmented NK activity induced by OK432 occurred even in patients with invasive tumors. On the other hand, the spontaneous NK activity in tissue-infiltrating lymphocytes (TIL) and lymph node lymphocytes (LNL) was significantly lower than that in PBL. In these three groups, the NK activity was significantly increased by OK432, this rate of increase was highest in TIL, followed by LNL and PBL. Further studies are required to elucidate the role of NK cells in bladder tumor, from the aspect of local and systemic immune responses.