CD4 and COVID-19: When we tested different subsets of T cells, we found that even though both helper T cells (CD3+CD4+) and suppressor T cells (CD3+CD8+) in patients with COVID-19 were below reference range (CD3+CD4+: 500–1700 cells/μL, CD3+CD8+: 244–1100 cells/μL), the lowering of helper T cells was considerably pronounced in fatal cases (184 vs. 353 cells/uL; p < 0.0001).