NCAM1 and COVID-19: On the contrary, CP donors with severe COVID-19 (hospitalized) comprised the group with the highest levels of NKT cells expressing the marker CD56 (CD3+CD56+CD16−) (8.29% vs. 1.8% of controls), compromising for the slightly lower percentages of the CD3+CD56−CD16+ NKT cell compartment (Figure 2D).