CD4 and COVID-19: From Kuri-Cervantes work and the work of others, we learned that compared to uninfected persons, severe COVID-19 is characterized by lower frequencies of lymphocytes8,15, total B cells8, total T cells8, CD4+ T cells8, CD8+ T cells8, CD8+ MAIT cells8, ILCs8, and NK cells8, as well as increased frequencies of neutrophils15,19 and monocytes8,15, and higher neutrophil-to-lymphocyte ratio.