As discussed by Pérez-Galarza, et al., there are several key roles considered for CD4 in mediating the immune response when related to COVID-19, including originating various phenotype T helper cells, such as Th1, to helping B cell create a long-lived antibody response, to helping CD8 expand the primary immune response, to stimulating natural killer cells’ cytotoxicity, to helping in viral clearance, and perhaps, memory CD4 helping to prompt immune defense systems [32]. This evidence concerns the gene CD4 and COVID-19.