ABBREVIATIONS
AA, aged healthy adults; ABC, age-associated B cell; ACO, aged COVID-19 onset patients; ACR, aged recovered COVID-19 patients; AH, aged healthy; ASC, antibody-secreting cell; BCs, B cells; CD4 Naive, naive CD4+ cells; CD4 Tcm, central memory CD4+ T cells; CD4 Tem, effector memory CD4+ T cells; CD4 Tex, exhausted CD4+ T cells; CD4 Treg, CD4+ regulatory T cells; CD8 CTL, cytotoxic CD8+ cells; CD8 Naive, naive CD8+ T cells; CD8 Tem, effector memory CD8+ T cells; CD8 Tex, exhausted CD8+ T cells; CyTOF, mass cytometry; DARs, differentially accessible regions; DCs, dendritic cells; DEGs, differentially expressed genes; DETs, differentially expressed transcription factors; GO, Gene Ontology; IFN-γ, interferon-gamma; Intermed, intermediate monocytes; MCs, monocytes; MEGAs, megakaryocytes; NK, natural killer; NK1, CD16− CD56bright NK; NK2, CD16+ CD56dim CD57− NK; NK3, the CD16+ CD56dim CD57+ late NK; NRF1, nuclear respiratory factor 1; PCA, principal component analysis; RBCs, red blood cells; RT-qPCR, quantitative reverse transcription polymerase chain reaction; scATAC-seq, single-cell assay for transposase-accessible chromatin sequencing; scRNA-seq, single-cell RNA sequencing; scTCR/BCR-seq, single-cell paired TCR/BCR sequencing; TCs, T cells; TFs, transcription factors; TNF, tumor necrosis factor; IL, interleukin; T-mito, mitotic T cells; t-SNE, t-distributed stochastic neighbor embedding; UMIs, unique molecular identifiers; YA, young healthy adults; YCO, young COVID-19 onset patients; YCR, young recovered COVID-19 patients; YH, young healthy.