Sex-Stratified Aging Trajectories Reshape Cell-Type–Specific Gene Programs in Human Peripheral Immunity

Columbia University, Department of Biostatistics, New York, New York, 10032, USA

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Abstract

Aging and sex are among the strongest determinants of immune phenotypes and multiple sclerosis (MS) risk, yet their joint transcriptional architecture in human blood cell subsets remains underdefined. Re-analyzing a sorted-cell bulk transcriptomic cohort (GSE137143) comprising CD4⁺ T cells, CD8⁺ T cells, and CD14⁺ monocytes from adults aged 19–72 years, we quantified gene-wise age-associated expression changes (age slopes), capturing the direction and magnitude of transcriptional change across adulthood, and constructed sex-stratified weighted gene co-expression networks (WGCNA) to group genes into coordinated biological programs. Module eigengenes (MEs), which summarize the overall activity of each co-expression module, were regressed on age with cell-composition covariates; functional interpretation was supported by dual Gene Ontology enrichment strategies (over-representation analysis and preranked GSEA) to link age-associated modules to immune-relevant pathways. We further developed a sample-resolved composite visualization that orders individuals by age and annotates per-module effect sizes (β) and statistical significance, making module activity trajectories interpretable at the individual-sample level. Cross-line validation demonstrated sign concordance between gene-level age slopes and ME-level age associations, supporting that the observed aging signals reflect coherent, program-level transcriptional trajectories rather than isolated gene-level fluctuations. At the gene level, significant aging-associated genes (FDR < 0.05) were most abundant in CD8⁺ T cells from females (329 genes) and CD4⁺ T cells from females (72 genes), with more modest signals in males (CD8_M: 10; CD4_M: 15) and none detected in monocytes. At the module level, aging was characterized by a robust age-associated down-regulation of cell-cycle and mitotic programs in T cells—most pronounced in CD8⁺ T cells (e.g., a representative cell-cycle module showed a strong negative age association, P = 1.48×10⁻⁸)—consistent with an age-related decline in proliferative capacity. In contrast, monocytes exhibited male-skewed activation of immune-receptor signaling pathways (including receptor-mediated signaling programs highlighted by GSEA) consistent with heightened innate immune activation in aging males. Female CD4⁺ T cells showed attenuation of nuclear-division programs (e.g., nuclear-division–related pathways showed significant negative age associations in females, P = 0.022), while several female monocyte/CD4 modules were annotated by cilium/cell-projection terms, suggesting sex-dependent remodeling of cellular structure and signaling with age. Together, these results delineate sex-specific aging trajectories across immune cell types and provide reproducible analytical outputs to facilitate reuse and independent validation.