The Immune System

The immune system becomes slightly less effective with aging. This is so slight that it is only noticed when infections linger or become severe. People who are infected with tuberculosis during early adulthood may have no symptoms until old age. Then, symptoms develop because the immune system is weaker.

The immune system may be less able to distinguish the body's own cells from foreign substances that invade the body.

Consequently, autoimmune disorders in which the immune system attacks some of the body's own cells become more common.

The cells of the immune system destroy cancer cells, bacteria, and other foreign substances more slowly.

This slowdown may be one reason that cancer is more common among older people. Also, vaccines tend to be less protective in older people. These changes in the immune system may help explain why some infections, such as pneumonia and influenza, are more common among older people and result in death more often.

The various age-related changes that influence our bodies' ability to resist and control infections include:

  • Barrier Defences
  • Physical And Mechanical Defences


The Barrier Defences

The skin and mucous membranes that line body cavities are primary barriers to infection by trapping organisms in secreted mucus and removing them by ciliary transport toward a body opening such as the mouth. Aging may compromise this barrier function, which commonly occurs in the mouth, urethra, and vagina.

Some of the barrier and antimicrobial properties of the skin may be impaired with age. In addition, certain skin conditions that predispose one to infection, including pressure ulcers wounds, lesions and bruises, become common.


Physical and Mechanical Defences

Difficulties in swallowing is a common and age-related change. This predisposes individuals to aspiration, drawing substances into the lungs instead of swallowing them through the oesophagus. This results in pneumonia, a common condition in older people.

Our cough mechanism decreases as we age, further reducing our ability to eliminate organisms. Changes in the lung, especially the collapse of small airways and the overall loss of lung elasticity, also increase the risks of infection.

In the gastrointestinal system, the stomach secretes reduced amounts of acid. The bowel's contractions can change, and out-pouchings called diverticula often form in the bowel lining. All of these changes make it easier for bacterial populations to increase in the gastrointestinal system.

Changes in the urinary tract lower resistance to infection due to:

  • Changes in the chemistry of the urine
  • Reduced prostatic fluid and a further reduction in its ability to kill organisms
  • Diminished flushing mechanism of the bladder and backward flow of bladder contents toward the kidney
  • Obstruction of urine flow by prostate enlargement, bladder prolapse, narrowing of the urethra, or kidney stones.

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Impaired Response

The white blood cells do not appear to change as we age, nor does their ability to attack organisms seem to be impaired. Whilst they continue to respond normally to signals to combat infecting organisms, should one develop fever with infections, reduced or absent fever responses are not rare.

An impaired response to a stimulus with age appears to be due to reduced numbers and diminished responsiveness of certain lymphocytes and other cell lines.

This decline in immune responsiveness may be responsible for our increased tendency to infections, cancer, and various immune diseases as we age.

On the positive side, due to our body's impaired production of antibodies in old age, allergy symptoms may become less severe.

How To Build Your Immune System

NEXT: Changes In Endocrine System With Age


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