The Immunological Theory of Aging

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The immunological theory of aging asserts that the process of human aging is, in fact, a mild and generalized form of a prolonged autoimmune phenomenon. Simply put, the theory holds that aging, which involves a highly complex series of processes, is largely controlled by the immune system. The process of aging is not fully understood in the medical and science communities and we still have not uncovered the primary cause, which is where theories like the immunological theory of aging come in.

Basics of the Immunological Theory of Aging

As humans age, we experience changes to almost all of our physiological functions, including immunity and immune system function. Medical experts have proven that immune function does indeed decrease with age, which contributes to a whole host of well-known issues among seniors, from increased health risks posed by common infections like a cold or the flu to a greater occurrence of chronic inflammatory diseases, such as gout and some types of arthritis. While the data suggests that changes in immune system function in the elderly could be a symptom of the aging process, proponents of the immunological theory of aging reverse the relationship. These theorists believe that our common symptoms of aging like chronic disease are caused by changes in the immune system.

The Aging Immune System

It is commonly known that the immune system changes that seem to accompany old age can have a direct impact on a person's longevity. The immune system is important in keeping our bodies healthy. Not only does it protect us against viruses and bacteria, but it also helps to identify and remove cancer cells and toxins. As we age, the potential for these elements to cause damage in our bodies increases.

But what is not known is what triggers these changes in immune system function and how they develop and progress. Research suggests that old age-related immune system dysfunction, sometimes known as "inflamm-aging," may, at least in part, cause and/or explain some aspects of the known aspects of the aging processes. Today, chronic inflammation is believed to contribute to a whole host of chronic and terminal diseases from cancer to Alzheimer's disease.

How Immune System Changes Might Affect the Body

Beyond being more prone to common viruses and bacterial infections, immune system changes have much greater impacts.

We know that as we age, the numbers of critical cells in the immune system decrease and become less functional. The immune system is made up of cells, substances, and organs. The thymus, spleen, tonsils, bone marrow, and lymphatic system, produce, store, and transport cells and substances, including B-lymphocytes and T-lymphocytes, antibodies, interleukins, and interferon. Those that are of special interest to gerontologists (scientists who study aging) are the class of white blood cells called lymphocytes, which fight invading bacteria and other foreign cells.

Lymphocytes fall into two major classes: B-cells and T-cells. B-cells mature in the bone marrow, and one of their functions is to secrete antibodies in response to infectious agents or antigens. T-cells develop in the thymus, which shrinks starting after puberty. T-cells are divided into cytotoxic T-cells and helper T-cells. Cytotoxic T-cells attack infected or damaged cells directly, which helper T-cells produce powerful chemicals, called lymphokines, mobilize other immune system substances and cells. While the number of T-cells remains fairly constant as we age, the proportion of them that proliferate and function declines. Furthermore, T-cells destroyed by cancer treatments such as chemotherapy and radiation take longer to renew in older people than they do in younger people.

The interleukins—of which there are more than 20—serve as messengers, relaying signals that regulate the immune response. Some, like interleukin-6, rise with age, and it is speculated that they interfere in some way with the immune response. Others, like interleukin-2, which stimulates T-cell proliferation, tend to decrease with age.

But when it comes to the immunological theory of aging, some research points to increasing immunogenetic diversification of human cells as the culprit, as opposed to the shifting numbers of cells. The theory holds that this increased diversification or cell mutation in old age may eventually lead to a failure of cell recognition and the breakdown of certain physiological systems, which ultimately triggers autoimmune-like reactions like chronic inflammation.

A Word From Verywell

Scientists continue to discover the complexities of the aging body and the many interdependent and interconnecting genetic, biochemical, and physiological processes involved. As this understanding grows, their findings could lead better health, less disability, and greater independence in later life, and potentially longer lifespans. 

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