The immune system helps protect your body from foreign or harmful substances. Some examples are bacteria, viruses, toxins, cancer cells, and someone else’s blood or tissues. The immune system produces cells and antibodies that destroy these harmful substances.
As you age, your immune system’s response slows down. This increases your risk of getting sick. Flu shots or other vaccines may not work as well or protect you for as long as expected.
An autoimmune disease can occur in which the immune system mistakenly attacks and destroys healthy tissues in the body.
There are fewer immune cells in the body for healing or detecting and correcting cell defects, and this can lead to an increased risk of cancer.
After the average age of 40, the immune system becomes less effective in the following ways:
- The immune system loses the ability to distinguish itself from foreign antigens. As a consequence, autoimmune disorders are more common.
- Macrophages (which ingest bacteria and other non-body cells) take longer to kill bacteria, cancer cells, and other antigens. This delay may be one of the reasons that cancer is more common after age 40.
- T-lymphocytes (reminiscent of antigens they have encountered before) respond more slowly to antigens.
- Fewer white blood cells (leukocytes) are able to respond to the new antigens. Therefore, when the body of the elderly encounters a new antigen, it is less able to remember it and to defend itself against its attack.
- With the years you have smaller amounts of complement proteins and not as many are produced as at younger ages in response to bacterial infections.
- Although the amount of antibodies that are produced in response to an antigen remains the same, the antibodies lose the ability to attack the antigen. These changes also partly explain why vaccines are less effective as we age.