FASLG and COVID-19: To interrogate the potential role of T cell activation–related biomarkers in COVID-19 immunopathogenesis, we measured levels of IL-2, sCD25 (or sIL-2Rα), soluble CD40 ligand (sCD40LG), soluble FAS ligand (sFASLG), IL-7, and IL-3 (Figure 3A, Supplemental Figure 10, and Supplemental Table 3).