CD56^bright and CD56^dim NK cell subsets exhibit differential receptor profiles and innate immune functions.

Many of the receptors and functions of CD56^bright (red cell) and CD56^dim (blue cell) NK cells are schematized in this figure. CD56^brightCD16^dim/neg NK cells produce abundant immunoregulatory cytokines (some of which are depicted here) and exhibit potent LAK activity but are less effective mediators of ADCC and natural cytotoxicity. By contrast, CD56^dimCD16^bright NK cells produce low levels of NK-derived cytokines and are potent mediators of ADCC, LAK activity, and natural cytotoxicity.11,12 CD56^bright NK cells have a less granular morphology when compared with CD56^dim NK cells.5 CD56^dim NK cell exhibit much higher levels of KIR, whereas resting CD56^bright NK cells have high expression of CD94/NKG2A.14,15 L-selectin is highly expressed on CD56^bright NK cells, whereas CD56^dim NK cells express PEN5/PSGL1 which appears to mediate interactions with L-selectin.15 16 ADCC, antibody-dependent cellular cytotoxicity; KIR, killer-immunoglobulin-like receptor; LAK, lymphokine-activated killer; NKRs, natural killer receptors.