Immunosenescence describes the gradual decline of the immune system with age. It affects both innate and adaptive immunity. This process weakens protection against infections and diseases.
The immune system changes profoundly as people grow older. Thymic involution occurs first. The thymus shrinks and produces fewer naive T cells. Consequently, the body relies more on memory cells.
Additionally, hematopoietic stem cells skew toward myeloid lineages. This shift reduces lymphoid cell production. Senescent immune cells accumulate over time. These cells secrete proinflammatory factors through the senescence-associated secretory phenotype (SASP).
Moreover, chronic low-grade inflammation, called inflammaging, rises. It stems from persistent stimuli like cell debris and gut dysbiosis. Inflammaging further impairs immune function.
T and B cells show clear dysfunction. Naive cells decrease while exhausted or senescent ones increase. Responses to new antigens weaken. Antibody production drops in quality and quantity.
These changes lead to serious effects. Older adults face higher infection risks. They include respiratory viruses, bacterial pathogens, and opportunistic infections. Cancer susceptibility grows due to reduced surveillance.
Furthermore, vaccine responses decline markedly. Standard doses often fail to build strong immunity. For instance, influenza or COVID-19 vaccines show lower efficacy in the elderly. Antibody titers remain modest. Cellular responses stay limited.
Researchers explore solutions actively. Adjuvants boost signals to immune cells. Higher antigen doses improve outcomes in some vaccines. Geroprotectors target pathways like mTOR to reverse aspects of decline.
In addition, lifestyle factors help mitigate effects. Exercise, balanced diet, and stress management support immune health. They reduce inflammaging and preserve function.
Scientists continue studying mechanisms deeply. They use systems immunology and omics tools. These efforts aim to develop targeted interventions.
In summary, immunosenescence drives age-related immune vulnerability. It combines structural changes, cellular exhaustion, and chronic inflammation. Understanding it guides better strategies for healthy aging and stronger vaccine protection in older populations.