CD56 does not contribute to the antitumor, tissue homing, and glycolytic capacity of human NK cells

Natural killer (NK) cells are critical innate immune cells involved in the clearance of virally infected and malignant cells. Human NK cells are distinguished by their surface expression of CD56 and a lack of CD3. While CD56 expression and cell surface density has long been used as the prototypic marker to characterize primary human NK cell functional subsets, the exact functional role of CD56 in primary human NK cells is still not fully understood. Here, we eliminated the expression of CD56 in human ex vivo expanded NK cells (CD56(bright)) using CRISPR/Cas9 in order to assess the function of CD56 in this highly activated and cytotoxic NK cell population. We show that the expression of CD56 has no effect on NK cell proliferative capacity or expression of various activation and inhibitory markers. Further, CD56 does not contribute to NK cell-mediated cytotoxicity, inflammatory cytokine production, or the ability of NK cells to control tumor engraftment in vivo. We also found that while deletion of CD56 did not impact NK cell glycolytic metabolism, it did increase NK cell reliance on oxidative phosphorylation. Last, CD56 does not alter expanded NK cell in vivo tissue trafficking. Our results indicate that while CD56 expression could be used to indicate a hyperfunctional state of NK cells, it does not directly influence the antitumor functions of expanded NK cells.