A prior study hypothesised that NKG2D downregulation on activated NK cells from patients with severe COVID-19 disease might be a consequence of cell-cell interactions since circulating monocytes of hospitalized COVID-19 patients expressed more ULBP-1 and -2/5/6 (ULBP3 expression was not studied) than healthy controls (65). The gene discussed is ULBP1; the disease is COVID-19.