CD4 and viral infectious disease: COVID-19 binds to ACE-2 receptors on respiratory epithelial cellsPoorly regulated pro-inflammatory response(see below) leading to impaired acquired immunity and dysregulated innate response.Direct viral infection of lymphocytes (71)Reduction of Dendritic cells, their maturation and function (41)T cell effects:Reduced CD4+ and CD8+ populations (82)*PD-1 upregulation (67)