Immunosenescence refers to age related changes in the immune system. This results in a weaker and more dysregulated immune system. It makes the individual more vulnerable to infections and malignancies and increased risk autoimmunity.
Understanding these changes are becoming more and more relevant as life expectancy, including those of patients with multiple sclerosis is becoming longer, with consequences for how MS itself behaves over time and also the implications for disease modifying therapies.
These changes happen in both, innate and acquired immunity. NK ( natural killer) cells that are part of innate immunity show impaired function . There is involution of the thymus gland important for T lymphocyte differentiation, with decreased T cell function and less new T cell production. Similarly, there is decreased function and new B lymphocyte production as well.
From natural history studies of MS, it appears that over time the disease becomes less inflammatory and less responsive to current medications. Alternatively, one may not need to continue these medications after a certain disease duration/age as the risk of a relapse or new lesions on MRI is minimal. Especially knowing that immune treatments may be associated with more risk in an weakened immune system due to age, we must reconsider and constantly weigh benefits vs risks when continuing older patients with MS on immune suppressive medications.
Jai S Perumal MD