NK cells and alphabeta- and gammadelta-CTL play important roles in cellular immunity against tumors. We previously demonstrated that NPC patients have a quantitative and qualitative deficit in gammadelta-CTL and EBV-specific alphabeta-CTL when compared to normal subjects and NPC long-term survivors. In this study we report further observations of a complementary activation of peripheral NK cells in NPC patients. The NK cells in these patients, compared to those of healthy subjects and NPC survivors, were preferentially activated in response to the stimulation of myeloma cell line XG-7 and expanded in the presence of exogenous IL-2. The production of IFN-gamma was lowest in the patient group, whereas IL-12, IL-15 and TNF-alpha were produced in higher levels in patients than in the donors and survivors. The cytolytic effect of the NK cells against NPC cells in the patient group was also higher than that of the donors and survivors. Furthermore, the patients at later stages of NPC had lower gammadelta-CTL activity but higher NK cytotoxicity towards NPC targets, with higher production of IL-12, IL-15 and TNF-alpha but lower production of IFN-gamma than in patients at earlier stages. This might be part of a triggered compensatory re-activation of the innate immunity, believed to be mediated through various cytokines and chemokines when adaptive T cell immunity is breached. Together, these data suggest complementary roles of innate and adaptive immune response in tumor immunity where NK cells, gammadelta- and alphabeta-CTL compensate for the deficits of one another at different stages of tumor invasion.