What Do We Know About Immune System Aging From Human And Animal Studies?
As we age, our body’s defense system, known as the immune system, undergoes significant changes, a process often referred to as “immunosenescence.” This age-related decline means our bodies become less effective at fighting off illnesses and responding to vaccinations.
One key aspect of this aging is “inflammaging,” a state of chronic, low-grade inflammation that persists even without an active infection. This constant internal alert contributes to many age-related health problems.
The changes aren’t just at a functional level; they affect the very organs and cells that make up our immune system. Primary immune organs like the bone marrow, where new blood cells are made, and the thymus, crucial for the maturation of T-cells (a type of white blood cell), experience a decline. This leads to fewer “naïve” immune cells, which are fresh cells ready to recognize new threats, and an accumulation of “memory” and “exhausted” cells, which have already encountered many pathogens and may be less responsive.
Specific immune cells also show age-related impairments. Neutrophils, macrophages, and dendritic cells, which are part of our immediate, non-specific immune response, become less efficient. Similarly, T and B lymphocytes, responsible for targeted and long-lasting immunity, show dysregulation. This means they don’t work as well to identify and eliminate specific threats, and the diversity of their “antigen receptors” (molecules that recognize foreign invaders) decreases.
These widespread changes are driven by fundamental cellular processes like “genomic instability” (damage to DNA), “epigenetic alterations” (changes in gene expression without altering the DNA sequence), “mitochondrial dysfunction” (problems with the cell’s powerhouses), and “telomere attrition” (shortening of protective caps on chromosomes). The accumulation of “senescent cells”—cells that have stopped dividing but remain active, releasing harmful substances (known as the senescence-associated secretory phenotype or SASP)—also plays a significant role in promoting inflammation and tissue damage.
Understanding these mechanisms is crucial because it paves the way for developing new treatments and lifestyle adjustments to lessen the negative impacts of immune system aging, ultimately helping us live healthier, longer lives.
Source: link to paper