CD4 and COVID-19: Severe cases of COVID-19 are often related with higher levels of D-dimer, lactate dehydrogenase, C-reactive protein (CRP), ferritin, interleukin (IL)-6, IL-10, IL-2R (soluble IL-2 receptor), and tumor necrosis factor alpha (TNF-a), which are also accompanied by an increased white blood cell counts (higher neutrophil counts) but lower absolute numbers of T helper (CD4+) and T cytotoxic (CD8+) lymphocytes, and decreased interferon gamma (IFNγ) expression by CD4+ T cells17,18.