[Immunogerontology--aging of the immune system and its cause]

Ageing is characterized by declining ability of the individual to adapt to environmental stress. By most parameters tested either in the laboratory or in vivo, immune function is decreased in elderly compared with young individuals. First age-associated changes in the immune system appear at the time of sexual maturity and result in the thymus atrophy. However, more drastic decrease of circulating T lymphocytes is observed in people over 70. Moreover, T cells respond weaker to mitogens, produce lower level of cytokines and cytokine receptors e.g. IL-2, IL-2R. Observed decrease of CD8+ T cells (T cytotoxic & T suppressor cells) results in an increase of CD4/CD8 ratio. Additionally, ageing also affects humoral response what consists in decrease in antibody producing cell number. Moreover, elderly individuals show increased level of serum IgG and IgA with parallel decrease of IgM. Seniors possess increased level of auto-antibodies and auto-anti-idiotopic antibodies. Innate immune responses are less affected with age. Adherence and phagocytosis of polymorphonuclears and macrophages is unchanged or even increased. However, their chemotaxis and synthesis of reactive oxygen metabolites is decreased. Reduced immunological vigor may result in the high incidence of infectious diseases, autoimmune diseases, immune complex diseases, and cancer.