CD4 and infection: The abnormal immune system and cytokine storm have been detected, such as the numbers of total T-cells, CD4 + T-cells and CD8 + T-cells are decreased, and the surviving T-cells are functionally exhausted [4], while the leukocytes, neutrophils, infection biomarkers and the concentrations of cytokines [interleukin (IL)-2R, IL-6, IL-8, IL-10 and tumor necrosis factor (TNF)-α] were significantly increased in patients with SARS-CoV-2 infection [5, 6].