As a concept, immuno-gerontology (the science of studying immunity and aging together) is a very recent focus of interest. Immune system has a role as a fundamental organ in prevention of diseases. Only recently, after the average life expectancy has increased and with more and more members of the population making it to 6 decades and longer, the study of immunology with respect to aging is attracting attention.
The immune system goes through a notable number of changes as a person ages. The disorders of the immune system stem from three major causes of disease in old age:
- Increased auto-immunity (tendency of the body to produce antibodies against their own tissues)
- Failing cellular surveillance leading to expression of cancer cells
- Increased susceptibility to infectious diseases
Along with the aging immune system, elderly also have other long term illnesses, exposures or conditions that complicate and contribute to the decline in immune system.
Changes in the human immune system with aging
As a person ages the immune cells like the T-cells, B-cells, etc. lose their function of recognising the offensive elements like bacteria, viruses, etc. And also there is decline in the defensive mechanism of these immune cells. The aging immune system fails to differentiate between the normal cell antigens from foreign antigens leading to increase in auto-immune diseases like SLE, Rheumatoid Arthritis, etc.
Clinical consequences of aging immune system
- Autoimmunity: The immune system recognises self antigens as foreign and produces antibodies against self-tissues, causing their destruction. Vasculitis, rheumatoid arthritis, ankylosing spondylitis are common old age illnesses.
- Cancer: The cancerous cells (or those cells having abnormal cell replication cycles) are recognised by an intact immune system and are killed before they can start invading the nearby tissue. This surveillance is damaged in old age leading to increased incidence of cancers in the elderly.
- Infections: With failing or delayed responses of the immune system to infective organisms, acquiring infection in old age is far more easier. Even trivial infections like the common cold take longer to recover.
Other causes of immune deficiency in old age, besides aging can be listed as:
- Co-morbid conditions like diabetes, obesity, etc.
- Pre-existing illnesses like COPD
- Poly-pharmacy (older persons tend to be on multiple medications)
- HIV and other infections
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