Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 73

To help define age‐related changes in the immune system, the term immunosenescence was introduced. The definition of immunosenescence covers all age‐related changes that result in decreased immune functions in the elderly. T cell function is necessary to kill mutated cells by direct cytotoxicity. The mucosal barrier function of the epithelium decreases with age. Thymus hypoplasia occurs, causing less T cell production as well as reduced T cell function. On the other hand, B cell function and number remain nearly stable. Innate immunity is little affected, while adaptive immunity is greatly affected in the elderly. Autoimmunity increases with age, with an excessive proinflammatory state and reduced T cell function playing a role. All of these changes lead to an increased prevalence of infections and malignant disease in the elderly.⁷¹

Inflammageing refers to additional immune pathological conditions due to comorbid conditions. The burden of chronic disease increases with age, resulting in a chronic inflammatory state. Excessive cytokine production and activation of B cells, neutrophils, and macrophages mediate this chronic inflammatory state. As a result, oxidative stress and reactive oxygen species (ROS) damage cellular DNA and impair the cell cycle, which may result in a malignant transformation of cells or tissue dysfunction. Inflammageing is one of the key factors affecting the biological ageing of the body and directly affects expected lifespan. It is a target for anti‐ageing research. Lifestyle changes aimed at reducing the incidence, progression, or burden of comorbidities may slow the inflammageing process.⁷² Some changes in the immune system are shown in Table 2.3.

Table 2.3 Changes in the immune system with age.

Decreased cell‐mediated immunity

Production of lower‐affinity antibodies

Increased autoantibodies

Decreased delayed‐type hypersensitivity

Decreased cell proliferative response to mitogens

Atrophy of thymus and loss of thymic hormones

Increased IL‐6

Decreased IL‐2 and IL‐2 responsiveness

Decreased production of B cells by bone marrow

Accumulation of memory T cells (CD‐45)

Impaired macrophage function

Facilitated production of anti‐idiotype antibodies

Increased NK cell number but decreased cytotoxicity

IL: Interleukin, NK: Natural Killer.