CD8+ T cells and NK cells: parallel and complementary soldiers of immunotherapy

[Display omitted] •CD8+ T cells and NK cells are both cytotoxic cells with engineering potential.•NK cells are comparable to CD8+ T cells but far less understood.•Cancer immunotherapies should target tumor-specific CD8+ T cells and NK cells.•Future therapies should integrate the power of CD8+ T cells and NK cells. CD8+ T cells and NK cells are both cytotoxic effector cells of the immune system, but the recognition, specificity, sensitivity, and memory mechanisms are drastically different. While many of these topics have been extensively studied in CD8+ T cells, very little is known about NK cells. Current cancer immunotherapies mainly focus on CD8+ T cells, but have many issues of toxicity and efficacy. Given the heterogeneous nature of cancer, personalized cancer immunotherapy that integrates the power of both CD8+ T cells in adaptive immunity and NK cells in innate immunity might be the future direction, along with precision targeting and effective delivery of tumor-specific, memory CD8+ T cells and NK cells.