Fig. 3: Modes of age-associated increased gene expression in CD8⁺ T cell subpopulations.

a Three distinct modes of gene expression increase with aging in CD8⁺ T cells. A representative gene is shown for each mode. From top to bottom, GZMA increases in the number of expressing cells (represented by percentage in a donor); B2M increases by expression level in cells (represented by percentage increase in UMI counts); and S100A4 increases by number of expressing cells and by expression level. Trend lines were from the lineage regression model for which the t distribution with n-2 degrees of freedom was used to evaluate if a slope was significant for a particular variable (2 sided t-test) used here and in c. b Classification of significant age-related increases in gene expression into three modes in each CD8⁺ T cell subpopulations (Na, naive adult; SCM, stem cell memory; CM central memory, EM1, 2, 3, effector memory subpopulations 1, 2, 3; EMRA1, 2 terminally differentiated effector memory cell subpopulation 1, 2, and EFF, effector cells) based on magnitude of change in percentage of detectable cells or average expression change in positive cells. The number and percentage of genes belonged to three modes were shown. Full gene list is in Supplementary Data 3. c Age-related mode of change at the protein level by flow cytometry. d Shared functional gene sets enriched in genes increasing with age in each of the three modes by gene set enrichment analysis (GSEA). The average significance defined by adjusted p-value (q) of each GSEA functional gene set analysis is represented in the heatmap in each cluster of CD8⁺ T cells by color scale. NES, normalized enrichment score. The scale of the magnitude of significance is 0 to 10⁻⁵. GO, gene ontology.