CD56^bright natural killer cells are present in human lymph nodes and are activated by T cell-derived IL-2: A potential new link between adaptive and innate immunity

Natural killer (NK) cells are innate lymphocytes that provide cytokines critical for early host defense against pathogens. One subset of human NK cells (CD56^bright) constitutively expresses the high-affinity interleukin 2 (IL-2) receptor and produces immunoregulatory cytokines. Here, we demonstrate that CD56^bright NK cells are present in human lymph nodes and that endogenous T cell-derived IL-2, acting through the NK high-affinity IL-2 receptor, costimulates CD56^bright NK cells to secrete IFN-γ. Thus, adaptive immunoregulators influence innate cytokine production, which in turn may influence the developing antigen-specific immune response. These data show a dynamic interaction between innate and adaptive human lymphocytes and emphasize the importance of studying interactions between immune components to understand the immune response as a whole.