IMMUNOSENESCENCE - INEVITABLE OR PREVENTABLE?

In humans, the immune system undergoes substantial change during the lifespan. Immunosenescence is defined as changes in the immune system that occur with ageing. These age-associated changes affect both innate and adaptive immune systems and contribute to increased morbidity and mortality in the elderly as a result of a higher incidence of infections, cancers and autoimmune diseases. Changes in T-cell lymphocyte populations and to a lesser extent the innate immune system are responsible for most of the decline in the protective immune response. These changes have largely been linked to a decline in the function of the thymus. However, these primary changes to the immune system are only evident at an advanced age. Secondary immunological changes (resulting from environmental influences) are far more frequent. These environmental factors include physical activity, nutrition, drugs and stress. The numerical and functional impairment of T cells and B cells from both primary and secondary influences on the immune system hampers response to vaccines. Following immunisation, older persons show decreased antibody concentration, delayed peak antibody titres and a faster decline in titres, especially in the very old and frail. Modification of environmental factors impacting on the immune system is essential, especially in the older population.