CD4 and COVID-19: T lymphocytes are also involved in the immune imbalance during COVID-19, with a massive decrease of CD4 and CD8 total numbers in the initial phase [37], and with CD4 T helper cells found in the pulmonary tract [45], showing a possible effect of SARS-CoV-2 on lymphocyte lysis and an important function of CD4 T helper cells in the lung damage in the acute phase [2, 45] (Figure 1).