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Sylvia S. Mader
Immagini e
concetti
della biologia
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
C6 - Lymphatic
and immune
system
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Lymphatic system
Lymphatic system has homeostatic functions and
comprises lymphatic vessels and organs.
•Lymphatic vessels transport lymph to the blood.
•Lymphatic organs produce and distribute
lymphocytes against pathogens.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Lymphatic vessels
Lymphatic vessels transport excess interstitial fluid
(lymph) to the cardiovascular system in a one-way
system.
Lymph contains H2O, proteins, ions, gas and
molecules for the immune response called
antibodies.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Lymphatic system
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Lymphatic organs
Lymphatic organs defend the body from pathogens
and are: the red bone marrow, the thymus
gland, the lymph nodes and the spleen.
Tonsils, Peyer patches and the appendix are
patches of lymphatic tissue that face pathogens
and antigens.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The red bone marrow
The red bone marrow is the
flexible tissue where the
blood cells are produced
and where B-lymphocytes
(B cells) mature.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The thymus gland
The thymus gland of the
thorax cavity educates Tlymphocytes (or T cells),
which are antigen-specific
cells of the immune system.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The lymph node
The lymph nodes are
distributed all around the
organism and are garrisons
of B, T and other immune
cells that cleanse the
lymph of pathogens.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The spleen
Similar in structure and
function to the lymph node,
the spleen functions as a
blood filter for pathogens
and debris.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The first defense
The first defense against
diseases is nonspecific
and innate.
It includes various ways
for contrasting pathogens.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The first defense
Barriers to entry include the skin, mucous membranes,
resident bacteria and antimicrobial molecules.
Complement protective
proteins are antigenactivated plasma proteins.
Interferon protective
proteins (cytokines) can
interfere with pathogen
replication.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The first defense
Phagocytes can be
neutrophils, eosinophils,
macrophages and dendritic
cells. They engulf
pathogens.
Natural killer cells (NK cells) provide quick response to
virus-infected and tumor cells.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The first defense
The Inflammatory response is a localized response to
pathogen attack associated with redness, warmth,
swelling and pain.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The second defense
The second line of defense against diseases is specific
as it recognizes, responds to and remembers specific
antigens.
Exogenous antigens: external antigens that entered the
body from the outside (i.e. bacteria or viruses).
Endogenous antigens: or self-antigens, are generated
within normal cell metabolism.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The second defense - fever
Fever is beneficial as it tells us something is
wrong.
Fever creates an unfavorable environment
for an invader.
Fever may stimulate the immune system.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The second defense
Active specific immunity
is long-lived and develops
naturally after infection.
It can be activated (induced)
by vaccination.
Passive specific
immunity is short-lived, it
occurs when a person is
given antibodies or when a
mother transmits antibodies
to her baby through
breastfeeding.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The second defense
Specific immunity responses depend on two types of
lymphocytes, both produced in red bone marrow:
•lymphocytes B, mature in the red bone marrow and are
responsible for antibody-mediated immunity;
•lymphocytes T, mature in the thymus gland and are
responsible for cell-mediated immunity.
Each B or T cell has an antigen receptor (BCR or TCR)
that binds to a specific antigen.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cells of the specific immunity
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Antibody-mediated
immunity
The clonal selection model.
•BCR combines with an antigen
•Activated B cells undergo clonal
selection
•Production of plasma cells (that
produce antibodies) and memory
cells (long term immunity)
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Antibody-mediated immunity
Vaccination is the use of antigens (a vaccine) to stimulate
the immune system to clone lymphocytes B and T.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cell-mediated immunity
The clonal selection model works for T lymphocytes too-
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cell-mediated immunity
For TCR to recognize a pathogen, the antigen must be
displayed to him by an antigen-presenting cell (APC)
along with a MHC protein.
(APC)
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cell-mediated immunity
The activated cell divides and, depending on the MHC,
produces either cytotoxic T cells (if MHC class I) or
helper T cells (if MHC class II).
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cell-mediated immunity
Cytotoxic T cells confer
cell-mediated immunity
and kill cancer, damaged or
infected cells.
Helper T cells coordinate
cell-mediated immunity and
antibody-mediated immunity
by releasing cytokines.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Monoclonal antibodies
Antibodies produced by cloned B cells are all
identical and monospecific.
Hence they are called monoclonal antibodies
and have many uses in both research and
medicine.
Monoclonal antibodies are used for medical
diagnosis, pregnancy testing and cancer
treatment.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Abnormal immune responses
Rejection of transplanted organs occurs
because the immune system distinguishes
between self and non-self, activating T cells.
Organ rejection after transplantation can be
controlled by immunosuppressive or
xenotransplantation.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Abnormal immune responses
Autoimmune disorders are long term diseases
in which immune system mistakenly attacks body
tissue.
•Rheumatoid arthritis: complement proteins, T
and B cells attack joints.
•Myasthenia gravis: antibodies attack
neuromuscular junctions.
•Systemic lupus erythematosus: the immune
system attack the nucleus of the body cells.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Abnormal immune responses
In coeliac disease, a food intolerance, the
immune system attacks the small intestine in
genetically predisposed people.
Coeliac disease is caused by gluten proteins
found in grains as wheat, causing inflammation
that damages the villi lining in the small intestine.
The only remedy is a lifelong gluten-free diet.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Abnormal immune responses
Allergies are hypersensitivities to certain allergens, as
pollen, food, animal fur, that produce an immediate
allergic response or a delayed allergic response.
Anaphylactic shock is a dangerous immediate response
characterized by a sudden drop in blood pressure.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cancer therapy
Cytokines are cell-signaling proteins that
stimulate white blood cells in immune responses.
Interferons, interleukins and tumor necrosis
factors (TNF) are cytokines used in cancer
therapy.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
AIDS
A person affected by Acquired Immunodeficiency
Syndrome can no longer respond the attacks of
antigens.
The syndrome results when immunodeficiency virus
(HIV) damages and destroys the T cells.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012