Aging changes in immunity

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Immune system structures

Overview

Aging changes in immunity

Information:

BACKGROUND

Aging is not synonymous with illness. However, getting older does increase the risk for many diseases and disorders. Overall, elderly people have an increased rate of chronic disorders, arteriosclerosis ("hardening of the arteries"), infections, autoimmune disorders, and cancer .

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This increased risk may be caused, in part, by the nature of these disorders. Most of the chronic disorders such as arteriosclerosis develop slowly and do not show symptoms until they have been progressing for years.

Another significant part of this increased risk is probably related to aging changes in the immune system. The immune system protects against diseases. It seeks out and destroys viruses, bacteria, fungi, and cancerous cells before they can damage the body. It learns to tell the difference between "self" tissue (normal body cells) and "non-self" particles (foreign invaders and abnormal cells).

AGING CHANGES

The thymus, one of the organs of the immune system, is the site where certain immune cells called T lymphocytes ("T cells") mature. The thymus begins to shrink (atrophy) after adolescence. By middle age it is only about 15% of its maximum size.

Some of the T cells directly kill foreign particles. Others help coordinate other parts of the immune system, which are specialized to attack different types of infections.

Although the number of T cells does not decrease with aging, T cell function decreases. This causes a weakening of the parts of the immune system controlled by these T cells.

EFFECT OF CHANGES

There is a slow, steady decrease in immunity after young adulthood. When the body is exposed to bacteria or other microorganisms (by an actual exposure or by immunization), fewer protective antibodies may be formed or they may be formed at a slower rate.

Flu shots or other immunizations may be less effective, and protection may not last as long as expected.

Later in life, the immune system also seems to become less tolerant of the body's own cells. Sometimes an autoimmune disorder develops -- normal tissue is mistaken for non-self tissue, and immune cells attack certain organs or tissues.

The immune system becomes less able to detect malignant cells, and cancer risk also increases with age as a result.

The immune system also becomes less able to detect foreign particles, and infection risk is greater.

Other things also increase the risk of infections. Sensation changes, gait changes, changes in the skin structure, and other "normal aging changes" increase the risk of injury in which bacteria can enter broken skin. Illness or surgery can further weaken the immune system, making the body more susceptible to subsequent infections. Diabetes, which is also more prevalent with age, can also lead to decreased immunity.