TNF and infection: In particular, these 16 genes that were highly expressed in ever uninfected individuals were mainly enriched in functions/pathways, such as cytokine-cytokine receptor interaction, TNF signal pathway, interleukin cell differentiation, and various pathogenic infection processes, suggesting that these individuals who never suffered from a COVID-19 infection might have stronger immunity such as higher levels of interleukin cell differentiation for anti-viral infection.