Transcript The Lymphatic System and Immunity

The Lymphatic System
and Immunity
Functions
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Production, maintenance, and distribution of
lymphocytes that provide defense against
infections and other environmental hazards
What is lymph?
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A fluid that resembles plasma but contains a
much lower concentration of suspended
proteins
Lymphatic Vessels
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Carry lymph from peripheral tissues to the
venous system
Superficial and deep lymphatics converge to
form lymphatic trunks which empty into two
large collecting vessels: the thoracic duct and the
right lymphatic duct
Blockage of the lymphatic drainage produces
lymphedema (condition in which interstitial
fluids accumulate and the limb gradually
becomes swollen and grossly distended)
Lymphocytes
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Account for 20-30 percent of the circulating leukocyte
population; produced in bone marrow and lymphoid
tissues
FYI: body has 1012 with a combined weight of more
than a kg
T-cells (thymus-dependent)
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Cytotoxic – attack foreign cells or body cells infected by
viruses
Helper – stimulate the activation and function of both T cells
and B cells
Suppressor – inhibit the activation and function of both T
cells and B cells
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B cells (bone marrow-derived)
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When stimulated, can differentiate into plasma cells,
which are responsible for the production and
secretion of antibodies
NK cells (natural killer)
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Attack foreign cells, normal cells infected with
viruses, and cancer cells that appear in normal
tissues
Lymphoid Tissues
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MALT (mucosa-associated lymphoid tissue)
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Collection of lymphoid tissues linked with the
digestive system
Tonsils
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Large lymphoid nodules in the walls of the pharynx
Lymphoid Organs
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Lymph nodes
1 mm to 25 mm
 Functions like a kitchen water filter, purifying lymph
before it reaches the venous circulation
 Fixed macrophages in the walls of the lymphatic
sinuses engulf debris or pathogens in lymph as it
flows past
 Provide an early-warning system
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Thymus
Pink, grainy organ located in the mediastinum
 Gradual decrease in size over lifetime
 Relation to disease in elderly?
 Produce T-cells
 Produces thymosin which promotes the
development and maturation of lymphocytes
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Spleen
Removal of abnormal blood cells by phagocytosis
 Storage of iron recycled from rbcs
 Initiation of immune responses by B cells and T
cells in response to antigens in circulating blood
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Nonspecific Defenses
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Physical barriers
Epithelium
 Secretions (mucus, acid)
 Hair
 Sweat gland duct
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Phagocytes
Remove cellular debris
 Attack and remove microorganisms
 Microphages and macrophages
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Immunological surveillance
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Constant monitoring of normal tissues by NK
cells
NK cell recognizes abnormal cell and adheres
Golgi apparatus aligns to face abnormal cell
Perforins diffuse from NK cell to abnormal cell
Perforins create a network of pores in abnormal
cell membrane
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Interferons
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Small proteins released by activated lymphocytes
and macrophages and by tissue cells infected with
viruses
Binds to surface receptors on the cell
Triggers the production of antiviral proteins in the
cytoplasm
Interfere with viral replication inside the cell
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Complement
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Proteins that complement the action of antibodies
Enhance the release of histamine by mast cells
Attract phagocytes
Makes the target easier to engulf
Destruct target cell membranes
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Inflammation
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Produces local swelling, redness, heat, and pain
Injury is temporarily repaired
Spread of pathogens away from the injury is slowed
Local, regional, and systemic defenses are mobilized to
overcome pathogens and facilitate permanent repairs
Fever
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Maintenance of body temperature greater than 37.2°C (99°F)
Pyrogens reset thermostat
Quicker mobilization of tissue defenses and an accelerated
repair process
Specific Defenses
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T cells are responsible for cell-mediated
immunity
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Defends against abnormal cells and pathogens inside
cells
B cells are responsible for antibody-mediated
immunity
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Defends against antigens and pathogens in body
fluids
Forms of Immunity
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Innate – genetically determined
Acquired immunity – only when exposed to
antigen
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Active – develops after exposure to antigen
Natural (over time)
 Induced (vaccine)
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Passive – produced by the transfer of antibodies
from another source
Natural (breast milk)
 Induced (antibodies against rabies virus)
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T-cells and Cell-mediated Immunity
p.371
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Antigen-bearing agents enter tissues.
An accessory cell phagocytizes the antigen-bearing agent and
lysosomes digest the agent
Antigens from the digested antigen-bearing agents are displayed
on the surface membrane of the accessory cell
Helper T cell becomes activated when it encounters a displayed
antigen that fits its antigen receptors
Activated helper T cell releases cytokines when it encounters a B
cell that has previously combined with an identical antigenbearing agent
Cytokines stimulate the B cell to proliferate
Some differentiate into antibody-secreting plasma cells
Antibodies combine with antigen-bearing agents, helping to
destroy them
B Cells and Antibody-Mediated
Immunity p.372
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Antigen-bearing agents enter tissues
B Cell becomes activated when it encounters an antigen
that fits its antigen receptors
Activated B cell proliferates, enlarging its clone
Some of the newly formed B cells differentiate further
to become plasma cells
Plasma cells synthesize and secrete antibodies whose
molecular structure is similar to the activated B cell’s
antigen receptors
Antibodies combine with antigen-bearing agents,
helping to destroy them
Types of Antibodies
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A.k.a. immunoglobulins
Soluble, globular proteins
IgG – effective against bacteria, viruses, and toxins
IgA – found in exocrine gland secretions (breast milk,
tears, nasal fluid, bile, urine)
IgM – develops in response to contact with certain
antigens in foods or bacteria
IgD – important in activating B cells
IgE – associated with allergic reactions
Antibody Actions
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Directly attack antigens
Active complement to
attack the antigens
Stimulate changes in
local areas that help
prevent the spread of
pathogens or cells
bearing foreign antigens
HIV Antibody test
Allergic Reactions
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An immune attack against a nonharmful substance,
such as chocolate
Can damage tissues
Antigens that trigger allergic responses are called
allergens
Delayed-reaction allergy – usually takes about 48 hrs to
occur; results from repeated exposure of the skin to
certain chemicals; may affect anyone
Immediate-reaction allergy – occurs within minutes
after contact with allergen; affects people who have an
inherited tendency to overproduce IgE antibodies
Anaphylactic Shock
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Severe form of immediate-reaction allergy in
which mast cells release allergy mediators
throughout the body
Entire body itches and breaks out in red hives
Vomiting and diarrhea may follow
Face, tongue, and larynx begin to swell and
breathing becomes difficult
Unless the person receives an injection of
epinephrine he or she will lose consciousness
and may die within 5 minutes
Transplantation and Tissue
Rejection
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Recipient’s immune system may recognize the donor’s
cell surfaces as foreign and attempt to destroy the
transplanted tissue, causing tissue rejection reaction
Immunosuppressive drugs are used to reduce rejection
Suppresses formation of antibodies or production of T
cells
Can leave a recipient unprotected against infections
How long can donated organs last outside of body?
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Heart: 3-5 hrs
Liver: 10 hrs
Kidney: 24-48 hrs
Autoimmunity
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Immune system fails to distinguish self from
nonself, producing autoantibodies and cytotoxic
T cells that attack and damage the body’s tissues
and organs
Type I diabetes mellitus, rheumatoid arthritis,
and systemic lupus erythematosus
HIV/AIDS
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HIV is the virus that
leads to the disease
AIDS
HIV finds and destroys a
type of white blood cell
(T cells or CD4 cells)
Scientists identified a
type of chimpanzee in
West Africa as the source
of HIV infection in
humans.
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HIV was first identified in the
United States in 1981
In 2006, an estimated 56,300 U.S.
individuals were infected with HIV.
about 1 million people in the
United States are living with HIV
or AIDS
Transmitted by
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Having sex (anal, vaginal, or oral)
with someone infected with HIV
Sharing needles and syringes with
someone infected with HIV
Being exposed (fetus or infant) to
HIV before or during birth or
through breast feeding
blood infected with HIV
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not transmitted through
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shaking hands
hugging
casual kiss
toilet seat
drinking fountain
doorknob
dishes
drinking glasses
Food
Pets
mosquitoes
Preventing Transmission
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Abstain from sex (do not
have oral, anal, or vaginal
sex) until you are in a
relationship with only one
person, are having sex with
only each other, and each of
you knows the other’s HIV
status.
Do not have sex when you
are taking drugs or drinking
alcohol because being high
can make you more likely to
take risks.
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Get tested for HIV
Talk about HIV and other
STDs with each partner
before you have sex.
Learn as much as you can
about each partner’s past
behavior (sex and drug use),
and consider the risks to your
health before you have sex.
Use a latex condom and
lubricant every time you have
sex.
Do not inject illicit drugs
Symptoms of HIV Infection
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rapid weight loss
dry cough
recurring fever or profuse
night sweats
profound and unexplained
fatigue
swollen lymph glands in the
armpits, groin, or neck
diarrhea that lasts for more
than a week
white spots or unusual
blemishes on the tongue, in the
mouth, or in the throat
pneumonia
red, brown, pink, or purplish
blotches on or under the skin
or inside the mouth, nose, or
eyelids
memory loss, depression, and
other neurological disorders
You cannot rely on
symptoms alone
because many
people who are
infected with HIV
do not have
symptoms for
many years.
 http://www.hivtest
.org/
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How HIV affects the immune system
HIV/AIDS Treatment
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Reverse transcriptase (RT) inhibitors interfere with the
critical step during the HIV life cycle known as reverse
transcription. During this step, RT, an HIV enzyme, converts
HIV RNA to HIV DNA. There are two main types of RT
inhibitors.
Protease inhibitors interfere with the protease enzyme that
HIV uses to produce infectious viral particles.
Entry and fusion inhibitors interfere with the virus' ability to
fuse with the cellular membrane, thereby blocking entry into
the host cell.
Integrase inhibitors block integrase, the enzyme HIV uses to
integrate genetic material of the virus into its target host cell.
Multidrug combination products combine drugs from
more than one class into a single product.
Types of disease transmission
Disease
Pathogen
Type of Agent
Spread by
Influenza (flu)
Orthomyxovirus
Virus
Casual contact
Chicken pox
Varicella-zoster
Virus
Casual contact
German measles
Rubella virus
Virus
Casual contact
AIDS
Human
immunodeficienc
y virus
Virus
Non-casual contact
Lyme disease
Borrelia burgdorferi
Bacterium
Insect bite
Measles
Morbilli virus
Virus
Casual contact
Mononucleosis
Epstein-Barr
virus
Virus
Casual contact
Syphilis
Treponema pallidum Bacterium
Sexual acts
Malaria
Plasmodium
Insect bite
Protozoa