Although frequency of CD8+ T cells is decreased, the intensity of CD8 co-receptor expression, as well as granzyme B and perforin levels, is higher in COVID-19 patients than in healthy individuals and mild patients [52-54], suggesting that even though CD8+ T cell numbers are low in COVID-19 patients, these cells are highly cytotoxic. The gene discussed is GZMB; the disease is COVID-19.