How Aging Affects Key Immune Cells
As we age, our bodies naturally undergo a wide range of physiological changes — but perhaps none are as critical to long-term health as the changes that occur in the immune system. One of the most significant of these changes is immunosenescence, or the gradual decline in immune function associated with aging.
This age-related deterioration helps explain why older adults are more susceptible to infections like the flu or COVID-19, and why their recovery often takes longer or becomes more complicated. In contrast, younger individuals typically bounce back more easily from these same illnesses, thanks in large part to a more robust and responsive immune system.
What Is Immunosenescence?
Immunosenescence refers to the decline in both the quantity and quality of immune cells over time. This shift impairs the body’s ability to mount an effective defense against pathogens and contributes to the increased risk of infections, cancer, and autoimmune diseases seen in older populations.
Interestingly, research indicates that this decline progresses more rapidly in men than in women. It involves changes in the number and function of various immune cells and alterations in inflammatory mediators throughout the body.
How the Immune System Changes with Age
Your immune system is powered by a complex network of white blood cells (WBCs) that circulate in your bloodstream (about five liters in the average adult). These cells act as your body’s defense army, identifying and eliminating pathogens, removing cellular waste, and maintaining balance in the immune environment.
However, as immunosenescence sets in, the composition and function of these immune cells begin to change in key ways:
T Lymphocytes
- Decreased numbers of naïve CD4+ and CD8+ T cells
- Reduced functionality of CD4+ helper cells and CD8+ cytotoxic T cells
- Decline in the generation of T helper (Th) cell subsets
Dendritic Cells
- Lower production of interferons (IFNs)
- Decreased expression of CD25 and ICAM-1 on mature dendritic cells
- Reduced lymphocyte cytotoxicity and an increase in monocyte-derived antigen-presenting cells
B Lymphocytes
- Reduced development and numbers of naïve B cells
- Less diversity in B cell repertoires
- Weakened antibody responses to new antigens
Macrophages
- Impaired phagocytic activity
- Lower cytokine production and antigen presentation capabilities
Neutrophils
- Reduced abilities in phagocytosis, chemotaxis, and programmed cell death (apoptosis)
Natural Killer (NK) Cells
- Decline in cytolytic potential and CD1 expression
- Decreased production of signaling molecules like cytokines and chemokines
These changes all contribute to a weakened immune defense system, leaving the body more vulnerable to disease and less capable of effective healing.
A Simpler Path to Longevity
In the ever-evolving world of longevity science, we often hear about the “12 Hallmarks of Aging” (a number that continues to grow as research expands). It’s easy to get overwhelmed by the array of molecules and supplements promoted for anti-aging — compounds like NMN, NR, resveratrol, quercetin, fisetin, glycine, taurine, and CA-AKG are just a few of the popular options.
While many of these show promise, they can interact with each other or with medications in complex ways that aren’t yet fully understood. What benefits one person might harm another, especially in populations with chronic illnesses or compromised immune systems.
That’s why it’s essential to return to safe, well-tolerated, and foundational interventions—solutions that can support the immune system in everyone, including older adults and those with comorbidities, without introducing unnecessary risks.
Why Immune Health Is Central to Lifespan
Aging remains the strongest risk factor for nearly all chronic diseases, including heart disease, cancer, Alzheimer’s, and more. Many scientists in the longevity field are advocating for aging itself to be formally recognized as a disease. If this shift in thinking takes hold, it could open up entirely new avenues for medical research and regulatory pathways—paving the way for targeted interventions that address aging as a root cause rather than simply treating its symptoms.
By tackling immunosenescence, we directly address one of the most impactful hallmarks of aging. Supporting immune function not only helps protect against infections but also enhances the body’s ability to respond to therapies, vaccines, and regenerative interventions.
