immune disorders
Effects of Aging on the Immune System
Older people
As people age, the immune system becomes less effective in the following ways: The immune system becomes less able to distinguish self from nonself (that is, to identify foreign antigens). As a result, Autoimmune Disorders become more common. Monocytes and Macrophages (which ingest bacteria and other foreign cells) destroy bacteria, cancer cells, and other antigens more slowly. This slowdown may be one reason that cancer is more common among older people. T cells (which remember antigens they have previously encountered) respond less quickly to the antigens. There are fewer White blood cells capable of responding to new antigens. Thus, when older people encounter a new antigen, the body is less able to remember and defend against it. Older people have smaller amounts of Complement System and do not produce as many of these proteins as younger people do in response to bacterial infections. Although the amount of antibody produced in response to an antigen remains about the same overall, the antibodies become less able to attach to the antigen. This change may partly explain why Overview of Pneumonia , These changes in immune function may contribute to the greater susceptibility of older people to some infections and cancers. 