TNFRSF18 and COVID-19: Furthermore, while the proportion of CD40L-expressing CD4+ T cells and that of ICOS-expressing CD8+ T cells was decreased in patients who recovered from COVID-19 as compared with patients with COVID-19 (Table 2), the fraction of OX40+ and GITR+ CD8+ T cells of patients who recovered from COVID-19 exceeded that of healthy controls, with the latter marker being the highest observed among all groups (Table 2).