Transcript Chapter 13 Physical Activity and the Immune System

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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 anti-inflammatory 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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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 Tcell receptor (TCR) on the cell surface. They do not have antigenpresenting properties (but rather, requiring B cells or NK cells for its
antigen-presenting 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: P353.
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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.