CD4 and COVID-19: Moreover, in elderly sepsis-induced ARDS patients compared to controls, we observed a significant decrease in CD4, CD3e, IL-7R, CD5, CD247, CD2, CD40LG, ITK, and KLRB1 gene expression levels, and a substantial elevation of MMP9, LCN2, and RETN, indicating their potential as targeted biomarkers for predicting COVID-19 and sepsis-induced ARDS in elderly patients.