GZMB and COVID-19: We also looked at the expression of HLA-DR in monocytes, and there was also an inverse correlation with clinical features associated to severity such as days in ICU, dead, CRP, D-dimer, etc. Altogether, these results indicate that activated T cells, high expression of granzyme B in NK cells and a shift in the expression of CD300 receptors are very significant features of patients with severe COVID-19.