Transcript 1 - Lone Star College

Lecture Outline
The Lymphatic System
and Body Defenses
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lymphatic System
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Three main functions
Fluid balance
Fat absorption
Defense
Lymphatic vessels
Form a one-way system
Begins with lymphatic capillaries
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Vessels merge and then enter one of two ducts:
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Tiny, closed-ended vessels
Take up excess tissue fluid (lymph)
Thoracic duct
Right lymphatic duct
Vessels have valves and movement of lymph
depends on skeletal muscle contraction
Edema is localized swelling caused by the
accumulation of lymph
Organs, Tissues, and Cells of the
Immune System
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Primary Lymphatic Organs
Lymphocytes originate and/or mature in
these organs
Red Bone Marrow
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Site of stem cells that produce blood cells
In an adult, red bone marrow is found in:
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Sternum
Vertebrae
Ribs
Skull
Part of the pelvic girdle
Proximal heads of the humerus and femur
Lymphocytes differentiate into B and T
lymphocytes
B lymphocytes mature in the red bone marrow
T lymphocytes mature in the thymus
Organs, Tissues, and Cells of the
Immune System
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Thymus Gland
In the thoracic cavity
Largest in children and shrinks as a
person ages
Lobules are filled with lymphocytes
Produces thymic hormones
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Aids in maturation of T lymphocytes
May have other functions in immunity
Critical to immunity
Organs, Tissues, and Cells of the
Immune System
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Secondary Lymphatic Organs
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Places where lymphocytes encounter and
bind with antigens
Spleen
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Largest lymphatic organ
Consists of two types of tissue:
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White pulp – has a concentration of lymphocytes
Red pulp – surrounds venous sinuses and is involved
in filtering blood
Blood entering the spleen is filtered through
venous sinuses
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Lymphocytes and macrophages react to pathogens
Macrophages engulf debris and remove old red blood
cells
Organs, Tissues, and Cells of the
Immune System
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Lymph nodes
Small structures occurring along lymphatic vessels
Connective tissue
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Forms a capsule
Divides node into compartments
Contains nodules packed with B lymphocytes
Sinus that contains T lymphocytes
Lymph passing through the sinus is filtered by
macrophages
T lymphocytes fight infection and attack cancer
cells
Lymphatic nodules
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Concentrations of lymphatic tissue not surrounded
by a capsule
Tonsils
Peyer patches
Appendix
Nonspecific and Specific Defenses
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Nonspecific Defenses
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Barriers to entry
Physical
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Intact skin
Mucous membranes
Chemical
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Sebaceous gland secretions
Lysozyme in perspiration, saliva, and tears
Urine
pH of the stomach
Normal flora
Nonspecific and Specific Defenses
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Inflammatory reaction
Four signs:
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Redness
Heat
Swelling
Pain
Nonspecific and Specific Defenses
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Inflammatory reaction
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5 steps
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Chemical mediators cause capillaries to dilate and
become more permeable
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Excess blood causes redness and increased
temperature
2. Increased permeability causes fluids and
proteins to escape the capillaries and cause
swelling
3. Edema and clot formation “wall off” the area
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Migration of phagocytes
Monocytes become macrophages that devour
pathogens and debris
Nonspecific and Specific Defenses
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Natural killer cells
Kill virus-infected cells and tumor cells
Large, granular lymphocytes
No specificity and no memory
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Protective proteins
Complement
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Composed of blood plasma proteins
Activated when pathogens enter the body
Amplify the inflammatory response
Bind to the surface of pathogens, ensuring that they
will be phagocytized
Form a membrane attack complex that punches
holes in the walls and membranes of bacteria
Interferon
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Produced by virus-infected cells
Produce substances that interfere with viral
replication
Nonspecific and Specific Defenses
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Specific Defenses
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Respond to antigens
Lymphocytes have antigen receptors
B lymphocytes
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Mature in the bone marrow
Give rise to plasma cells that produce
antibodies
T lymphocytes
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Mature in the thymus gland
Directly attack cells that have nonself proteins
or regulate the immune response
Nonspecific and Specific Defenses
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Clonal Selection
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When B cells encounter an antigen they are activated
to divide many times
Plasma cells – mature B cell that produces
antibodies
Clones
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Most mature to form plasma cells
Some become memory cells
Make long-term immunity possible
A second exposure to the same antigen produces
a stronger, faster immune response
Plasma cells undergo apoptosis when an
infection has passed
Nonspecific and Specific Defenses
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Structure of Antibodies
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Basic unit is a Y-shaped protein molecule with two
arms
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“heavy” polypeptide chain
“light” polypeptide chain
Chains have constant regions at the trunk of the Y
The class of antibody is determined by the structure
of the constant region
Monomers – single Y-shaped molecules
Dimers – paired Y-shaped molecules
Pentamers – clusters of 5 Y-shaped molecules linked
together
Function of Antibodies
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Neutralization
Forming immune complexes
Nonspecific and Specific Defenses
Nonspecific and Specific Defenses
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T Cells and Cell-Mediated Immunity
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Antigen must be presented to T cells by an
antigen-presenting cell
Major histocompatability (MHC) proteins
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T cell compares the antigen and the self
protein
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Called HLA (human leukocyte antigens)
Are self proteins
Activated T cell and all daughter cells can
recognize “foreign” from “self”
Will destroy cells carrying foreign antigens
Activated T cells produce cytokines that
stimulate various immune cells to perform
their functions
Nonspecific and Specific Defenses
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Types of T Cells
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Cytotoxic T cells
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Destruction of virus-infected or cancer
cells
Have storage vacuoles containing Perforin
molecules
Responsible for cell-mediated immunity
Helper T cells regulate immunity by
secreting cytokines
Nonspecific and Specific Defenses
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Cytokines in Cancer Chemotherapy
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Used as immunotherapeutic drugs
Interferon and interleukins are also
used as immunotherapeutic drugs
Creating and Immune Response
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Active Immunity
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Often develops naturally
Immunization
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Involves the use of vaccines
After the first exposure, a primary
response occurs
A second exposure (“booster”) produces a
secondary response
Depends on the presence of memory
cells
Usually long-lasting
Creating and Immune Response
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Passive Immunity
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Occurs when an individual is given
prepared antibodies
(immunoglobulins)
Is temporary
Can be used in the event of an
unexpected exposure to an infectious
disease
Creating and Immune Response
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Monoclonal Antibodies
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Every plasma cell derived from the
same B cell
Secretes antibodies against one
antigen
Can be produced in vitro
Are being used for quick and certain
diagnosis of various conditions
Used to carry radioactive isotopes or
toxic drugs to tumors
Creating and Immune Response
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Hypersensitivity Reactions
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Allergies
Response to substances that are harmless to the
body (allergens)
IgE-Mediated Allergic Response
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Immediate allergic response
Caused by IgE antibodies
When an allergen attaches to the IgE antibodies,
histamine is released
Anaphylactic shock occurs when the allergen has
entered the blood stream
T-Cell Mediated Allergic Response
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Initiated by memory T-cells at the site of allergen
contact
Regulated by cytokines
Creating and Immune Response
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Tissue Rejection
Transplanted tissue is recognized as not
“self”
Cytotoxic T cells cause disintegration of
the transplanted tissue
Can be controlled by:
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Selecting organs that have the same type of
HLA antigens as those of the recipient
Administering immunosuppressive drugs
Creating and Immune Response
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Autoimmune Diseases
Cytotoxic T cells or antibodies attack the
body’s own cells
Cause is unknown
Examples:
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Myasthenia gravis
Multiple sclerosis
Systemic lupus erythematosus
Rheumatoid arthritis
No cures, but can be managed with
medications
Creating and Immune Response
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Immune Deficiency
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The immune system is unable to protect
the body from disease
Can be acquired or genetic
Without treatment, common infections
can be fatal
Effects of Aging
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Aging people become more
susceptible to infections and
disorders
Thymus gland degenerates and
number of T cells decreases
B cells sometimes do not form
clones
Incidence of autoimmune diseases
increases
Response to vaccines is decreased
Homeostasis
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The lymphatic system helps the following:
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Nonspecific immune responses are dependent
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The digestive system by absorbing fat
The cardiovascular system by absorbing lymph
The immune system in protection against infectious
diseases
The skin
Mucous membranes of the respiratory tract, the
digestive tract, the reproductive and urinary systems
Specific defenses are dependent on blood cells
There is a strong connection between the
immune, nervous, and endocrine systems