Aging, effects on immune response
At birth the IMMUNE SYSTEM is fairly undeveloped. The infant relies largely on the carryover of maternal immune components for about the first six weeks of its life, while the infant’s body builds its own immune system. By age four months, maternal IMMUNITY wears off and the infant’s immune system is on its own (though an infant who is BREASTFEEDING continues to receive antibodies and limited immune support from his or her mother). Immunity reaches full STRENGTH in early childhood, a level at which it continues until about age 40.
After age 40, the effectiveness of the immune system begins to diminish. T-cell lymphocytes and macrophages respond more slowly. Levels of complement (protein factors essential for ANTIBODY-ANTIGEN binding) and of antibodies drop off. The immune system is slower to differentiate B-cell lymphocytes to antigen-producing PLASMA cells, and plasma cells produce lower quantities of antibodies. The immune response to disease as well as to vaccines becomes slower and less effective, increasing susceptibility to serious INFECTION (such as INFLUENZA and PNEUMONIA) from pathogens. The amounts and activity of MUCOSA-ASSOCIATED LYMPHOID TISSUE (MALT) decrease in areas such as the LUNGS, further reducing the body’s ability to reject infection from invading pathogens. Decades of exposure to antigens mean more lymphocytes are sensitized for specific antigens, leaving fewer to become sensitized to new antigens. The IMMUNE RESPONSE summons T-cell lymphocytes less quickly to the scene of an infection.
Changes in antigens and antigen recognition also occur, resulting in a decreased ability of the immune system to distinguish between self and nonself antigens. Cells may acquire a mix of antigens that makes them appear foreign, initiating an inappropriate immune response (autoimmune disorder) that damages an organ or structure. Or the immune system may fail to detect the change in antigens on the surfaces of cell membranes of cells that become cancerous, allowing cancer tumors to develop. AUTOIMMUNE DISORDERS and cancer consequently become more common with advancing age.
Measures to prevent infection can help offset age-related immune changes to some degree. Diligent HAND WASHING and avoiding exposure to other people who have COLDS or influenza may prevent the spread of these infections. ECHINACEA and GOLDENSEAL are herbal remedies that can boost immune function after an exposure to common pathogens. GAMMAGLOBULIN may boost the immune response in circumstances such as exposure to HEPATITIS. Older people often benefit from more aggressive antibiotic therapy-ANTIBIOTIC MEDICATIONS administered early in the infection process-to help them fight infections they do develop.
See also ANTIBODY-MEDIATED IMMUNITY; CELL-MEDIATED IMMUNITY; COMPLEMENT CASCADE; HEALING; IMMUNOSENESCENCE; LYMPHOCYTE; MACROPHAGE; T-CELL LYMPHOCYTE.
