SELL and COVID-19: Intriguingly, the increased activation status was inversely correlated with protein expression of the trafficking molecule CD62 Ligand (CD62L) (Figures 1F, G), a marker associated with cell naivety (22) encoded by the gene SELL. CD62L protein expression was significantly lower in all three ILC subsets in COVID-19 patients, indicating that these cells were more mature (Figure 1G).