GZMB and COVID-19: The phenotypic profile of NK cells in non-severe SARS-CoV-2 infection is characterized by an increase in the expression of CD69, CD38, HLA-DR, Lag-3, Tim-3, and TIGIT, with an increase in the production of perforin, MIP-1b, and granzyme B. On the other hand, the phenotypic profile of NK cells in patients with severe illness showed an increase in KIR receptors, CD57, NKG2C, and IL-15R, along with a reduction in the production of perforin and granzyme B. It has been postulated that in patients with severe COVID-19, there is a high abundance of CD56dim NK cells in peripheral blood [8].