Lymphocyte subsets play an important role in cellular immune regulation, and SARS-CoV-2 infection has been reported to primarily impact T lymphocytes (especially CD4+ T and CD8+ T cells), which means that T lymphocytes might be highly involved in the pathological process of COVID-19 and provide an important defense against COVID-19 [12, 15]. This evidence concerns the gene CD4 and COVID-19.