Introduction The immune system isn't just a casualty of aging—it's a primary driver. Research shows that senescent immune cells propagate inflammaging via SASP factors like IL-6 and TNF-α PMC12651686, and an aged immune system directly induces senescence in solid organs Nature. This creates a vicious cycle: dysfunctional immune cells fail to clear senescent cells, accelerating their accumulation Nature Comms. Partial epigenetic reprogramming with Yamanaka factors (OSKM) shows promise in rejuvenating aged cells, but its specific application to immune cells remains untested Gladstone, Stanford.

Hypothesis We propose that cyclic, immune-specific expression of OSKM in T cells will reverse immunosenescence and attenuate systemic aging by restoring mitochondrial function, reducing SASP secretion, and enhancing cytotoxic clearance of senescent cells. This leverages the unique position of T cells as both inflammation amplifiers and senescent cell eliminators.

Novel Mechanistic Reasoning Beyond general epigenetic rejuvenation, we focus on T cell mitochondria. Dysfunctional mitochondria in aged T cells drive inflammaging and limit their effector functions, directly linking immunometabolism to age-related diseases Science. OSKM reprogramming could reset mitochondrial biogenesis and dynamics—via pathways like PGC-1α activation and fission/fusion balance—improving metabolic fitness. Healthier T cells would secrete fewer pro-inflammatory cytokines (e.g., IL-6, TNF-α) and potentially shift to an anti-inflammatory profile, dampening SASP from other immune cells like macrophages and age-associated B cells PMC12834418. Moreover, rejuvenated T cells may regain cytotoxic efficacy, directly killing senescent cells that upregulate stress ligands (e.g., NKG2D ligands), breaking the clearance failure cycle. This dual action—reducing SASP production and boosting clearance—could synergistically lower the systemic senescent cell burden, a mechanism not yet explored in existing studies.

Testable Predictions

1. In vivo models: In aged mice, cyclic OSKM expression specifically in T cells (using Cre-lox systems targeting CD4 or CD8 promoters) will reduce circulating SASP factors (IL-6, IL-1β, TNF-α) and lower markers of inflammaging within 8–12 weeks.
2. Cellular assays: Treated T cells will show improved mitochondrial function (increased oxygen consumption rate, reduced ROS) and enhanced in vitro cytotoxicity against senescent fibroblasts, measurable via co-culture assays.
3. Systemic outcomes: Compared to controls, treated aged mice will exhibit reduced fibrosis in kidneys and liver (via histology), improved cognitive performance (Morris water maze), and better metabolic health (glucose tolerance tests).
4. Falsifiability: If T cell-specific reprogramming fails to reduce senescent cell load (quantified by p16^INK4a staining) or improve organ function despite confirmed epigenetic changes (e.g., DNA methylation age reversal), the hypothesis is invalid.

Implications If validated, this would establish immune-specific reprogramming as a targeted anti-aging therapy, potentially slowing multiple age-related diseases by breaking the inflammaging-senescence cycle at its root. It could inform combination approaches with senolytics or other immune modulators, offering a precision medicine angle for aging interventions.