SPDL1 and COVID-19: We thus assessed plasma levels of soluble PD-1 (sPD-1) and soluble PD-1 ligand PD-L1 (sPD-L1) — as well as the expression of PD-1– and PD-L1–targeting miRNAs miR–138-5p, miR–15a-5p, miR–16-5p, and miR–28-5p in CD4+ and CD8+ T cells — and the extent of PD1 promoter DNA methylation in CD4+/CD8+ T cells isolated from patients who recovered from COVID-19 as compared with those with COVID-19 and healthy controls (Figure 3, G–M).