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“Those who think they have not time for bodily exercise will sooner or later
have to find time for illness.”
~Edward Stanley
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The possibility that moderate levels of physical activity may have on the immune system is a
likely explanation for general benefits that might extend to several types of cancers.
Persistent Inflammation may be a part of the pathogenesis in tumor growth and development
of atherosclerosis, insulin resistance and neurodegenerative diseases of the CNS so—regular
exercise may help against CVD, NIDDM, dementia, and depression through antiinflammatory effects either by reduction in abdominal fat that secretes inflammatory
cytokines or through release of anti-inflammatory myokines during skeletal muscle
contraction.
The acute effects of exercise on the immune system were first reported over 100 years ago,
when German physiologist G. Schulz (1893) noted that muscle contractions produced an
increase in the number of leukocytes circulating in the blood.
Physical activity may also influence the risk of infection. (some increase/some decrease).
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Hypothesis: physical inactivity leads to the accumulation of
visceral fat and consequently to the activation of a network of
inflammatory pathways, which promote the development of
insulin resistance, atherosclerosis, neurodegeneration and
tumor growth, leading to the development of “the diseasome
of physical inactivity”.
©2011 by The Company of Biologists Ltd
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Whether activity affects the immune system in a way that meaningfully reduces the
risk of developing cancer or other chronic diseases is even less well established. No
studies have shown such benefits among humans.
The immune system is an integrated network of molecules, cells, tissues, and
organs that defend an organism against infections by foreign substances
(bacteria/viruses) and against mutated native cells (tumors). It also helps to repair
damaged tissues and to clean up the debris of dead cells (after muscle injury).
2 types of immunities: (1) Innate (natural) and (2) adaptive (acquired).
Innate means that immune cells can recognize a foreign substance (antigen)
without prior exposure.
Adaptive refers to immune cells memory whereby they recognize a pathogen from
prior encounter, permitting a quicker and larger immune response upon a
subsequent exposure.
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Innate immunity provides the initial defense against various infectious agents and
cancer. It can be activated by pathogens to which an organism is exposed through
contact with skin, inhalation, or ingestion of food and water. Innate immunity can
also be activated by tissue necrosis (muscle damage through exercise) or release of
heat shock or oxidative stress proteins from the liver, heart and skeletal muscle.
Adaptive or acquired immunity is able to recognize highly specific antigens as a
result of previous exposure and offers different responses to different types of
microbes.
Cells of the Immune System: Leukocytes—white blood cells; Lymphocytes are the
major cells of adaptive immunity.
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An antibody (Ab), also known as an immunoglobulin (Ig), is a large Y-shaped
protein produced by B-cells that is used by the immune system to identify and
neutralize foreign objects such as bacteria and viruses. The antibody recognizes a
unique part of the foreign target, called an antigen.[1][2] The production of
antibodies is the main function of the humoral immune system.[3
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T cells or T lymphocytes are a type of lymphocytes (itself a type of white blood
cells) that play a central role in cell-mediated immunity. They can be distinguished
from other lymphocytes, such as B cells and natural killer cells (NK cells), by the
presence of a T-cell receptor (TCR) on the cell surface. They do not have antigenpresenting properties (but rather, requiring B cells or NK cells for its antigenpresenting property). They are called T cells because they mature in the thymus.
Natural Killer cells are a class of large, granular lymphocytes found in blood and
lymphoid organs, especially the spleen. They do not require prior exposure to
recognize an antigen and thus play an important role in innate immunity. Acute
exercise increases the numbers and possibly the activity of NK cells in the blood.
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The Thymus Gland Imagine one gland in the body which is as
big as a man’s fist when we are born controlling how we react
and whether we are immune to life, comments or disease. And
this one gland shrinks to the size of our thumbnail, as we get
older. This crucial gland is the THYMUS gland.
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Monocytes are a type of white blood cell and are part of the innate immune system of
vertebrates including all mammals (humans included), birds, reptiles, and fish. Monocytes
play multiple roles in immune function. Such roles include: (1) replenish resident
macrophages and dendritic cells under normal states, and (2) in response to inflammation
signals, monocytes can move quickly (approx. 8–12 hours) to sites of infection in the tissues
and divide/differentiate into macrophages and dendritic cells to elicit an immune response.
Half of them are stored in the spleen
Monocytes and macrophages are phagocytes. Macrophages function in both non-specific
defense (innate immunity) as well as help initiate specific defense mechanisms (adaptive
immunity) of vertebrate animals. Their role is to phagocytose, or engulf and then digest,
cellular debris and pathogens, either as stationary or as mobile cells. They also stimulate
lymphocytes and other immune cells to respond to pathogens. They are specialized
phagocytic cells that attack foreign substances, infectious microbes and cancer cells through
destruction and ingestion
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Granulocytes are a category of white blood cells characterized by the presence of
granules in their cytoplasm.
Some chemokines control cells of the immune system during processes of immune
surveillance, such as directing lymphocytes to the lymph nodes so they can screen
for invasion of pathogens by interacting with antigen-presenting cells residing in
these tissues.
Interferons (IFNs) are proteins made and released by host cells in response to the
presence of pathogens such as viruses, bacteria, parasites or tumor cells. They
allow for communication between cells to trigger the protective defenses of the
immune system that eradicate pathogens or tumors.
Cytokines mediate both innate and adaptive immune responses: P-353.
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Organs of the Immune System: Immune cells migrate to and are concentrated in the
primary and secondary lymphoid organs. The primary are bone marrow
(hematopoiesis—generation of blood cells) and the thymus where thymocytes
mature to become T lymphocytes.
Secondary: is where contact between lymphocytes occurs—lymph nodes, spleen
and cutaneous immune system.
Eccentric muscle contraction: P-361
NK cells after exercise:
Overtraining and Immune Suppression in Athletes: P-366.
Type of
exercise
Acute
Increases
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Chronic
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Blood levels of
granulocytes (mainly
neutrophils)
Blood levels of
monocytes
Phagocytic activity of
macrophages
Blood levels of NK
cells
NK cell cytotoxicity?
Risk of upper
respiratory infection
(strenuous exercise)
Decreases
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Blood levels of T
lymphocytes
NK cell cytotoxicity
(strenuous exercise)
Risk of upper respiratory
infection (moderate
exercise)
Tumor growth