The Lymphatic System, Immunity, and Aging
As an individual ages, the resistance to all types of infection is decreased. Malignancies are more com-mon in the elderly. The immune response to vaccines is also diminished. The incidence of autoimmune diseases increases, which may be a result of the over-all decrease in immune function. Natural killer cell activity decreases, leading to the proliferation of ab-normal cells such as cancer cells. The number of T lymphocytes diminishes with age. Both T and B lym-phocytes become less responsive to antigens; atro-phy of the thymus with resultant decrease in hor-mone secretion may play a part in this decreased response. B cell function is decreased and the quan-tity of antibodies produced when the body is chal-lenged with antigens is reduced.