CD4 and COVID-19: As demonstrated in Fig. 6C, UMAP plots showed the 9 subclusters of T cell, B cell, and NK lymphocyte subsets, including naïve CD4+ cells, macrophages, effector memory (TEM) CD8+ T cells, B cells, megakaryocytes, CD8+ cells, natural killer cells, T cell, and monocyte-derived dendritic cells in COVID-19 patients and healthy controls, and three unknown subclusters were also identified (Fig. 6C).