Immunosenescence and multiple sclerosis.

Changes in the immune system associated with ageing are known as immunosenescence. This is characterised by a decline in immune response, chronic inflammation and an increased risk of autoimmune diseases. A chronic inflammatory process with persistent production of proinflammatory mediators increases the risk for morbidity and mortality related to age, and has been dubbed 'inflamm-ageing'. Immunosenescence is associated with a decrease in the number of naive T and B cells, NK cells and disruption of the pro- and anti-inflammatory balance by changes in the production of cytokines. In fact, ageing of the immune system has a complex network of underlying causes which include not only natural mechanisms of senescence but also chronic disorders, lifestyle, environmental and epigenetic factors, and infections. Moreover, immunosenescence has an influence on the course of chronic diseases which have an onset in young adults, such as multiple sclerosis (MS). Current disease modifying therapies (DMTs) in MS aim to reduce the frequency of relapses and to slow disease progression, but they do not necessarily stop the accumulation of disability related to disease progression. Some features of immunosenescence found in aged healthy controls are already observed in MS patients at a younger age. The older population is characterised by an increased susceptibility to infections, a poor response to vaccinations, and a higher risk of developing cancer, vascular diseases and neurodegeneration. Immunosenescence is an important factor influencing the course of MS, and the safety and effectiveness of DMTs. The relationship between the pathogenic process underlying the development of MS and immunosenescence requires further investigation.