To investigate the involvement of NK cells in the pathogenesis of COVID-19, CD3−CD16+CD56dim and CD3−CD16−/+CD56bright NK cell subsets and their NKp30, NKp44, NKp46, NKG2A, NKG2D, CD57 and CD38 expression levels were detected by flow cytometry. Here, KLRC1 is linked to COVID-19.