Transcript Immunity - sjebiol

IMMUNITY
Makes the bad pathogens die!
THE IMMUNE SYSTEM

Involves
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The lymphatic system
The circulatory system
Bone marrow
The lymphatic system
can carry the plasma
and white blood cells
from the circulatory
system
 Lymph nodes are a
common ‘collection’
site

FOREIGN BODIES
Any cells not recognised as ‘self’ cells
 ‘Self’ cells are recognised by the immune system
by MHC (Major Histocompatibility Complex)
markers on the surface
 MHC markers are specific antigens found on the
surfaces of all cells

MHC 1 Markers are found on all cells, except RBC
 MHC 2 Markers are found on immunity cells (B cells,
T cells and some monocytes

Cells lacking recognised MHC markers are
deemed ‘non-self’ and attract an immune
response
 Non-self markers that trigger a response of B
cells or T cells are called antigens
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SELF AND NON-SELF RECEPTORS
THREE LINES OF DEFENSE

1st line
non-specific
 Blocks foreign bodies from entering tissues
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2nd line
non-specific
 Attacks foreign bodies in tissues
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3rd line
Specific
 Has a ‘memory’
 Involves cell differentiation
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1ST LINE
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Mucous membranes
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Secretions
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Secreted by cells to ‘trap’ foreign particles
Includes tears, mucous, sweat, etc
Cilia
Fine hairs lining the trachea
 Sweep foreign particles back to the oesophagus
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Skin
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Acts a barrier between internal environments (tissue)
and external environments
Natural flora
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Symbiotic bacteria
2ND LINE

Phagocytes

WBC which engulf and destroy foreign cells
Neutrophils (made in bone marrow)
 Monocytes (made in bone marrow)
 Monocytes become macrophages when they enter the blood
stream
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Natural Killer (NK) cells
Acts on viral-infected cells
 Release perforins (protein) which act to lyse infected
cells
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COMPLEMENT PROTEINS
About 20 types
 Made in the liver
 Inactive until infection occurs
 Antibody-antigen complex attracts them to site of
infection
 Three ways to act

Stick to the bacteria to aide identification
 Destroy membrane of pathogen
 Stimulate pahgocytes to become more active
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INTERFERON
Secreted by cells infected by virus
 Acts on local cells to avoid further infection
 Stimulates antiviral protein production
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CYTOKINES
Protein messenger
 Messages between immunity cells
 Messages to nervous system
 Secreted by many cells (particularly T cells)
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INFLAMMATION
Controlled by multiple enzymes and compounds
 Mast cells, basophils and platelets all release
messengers to encourage inflammation
 Inflammation involvse the dilation of blood
vessels at the site of infection
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This brings more white blood cells
 It also accounts for the symptoms of swelling, redness
and heat
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The first phagocytes to the area release
histamine, this attracts more phagocytes
 Pus is generated from dead white blood cells
containing the pathogen
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3RD LINE OF DEFENSE
Specific immunity
 Part of acquired immunity
 All lymphocytes originate in the bone marrow
 B cells
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mature and differentiate in the bone marrow
Involved in humoral responses
T cells
Mature and differentiate in the thymus
 Involved in cell-mediated responses
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TYPES OF CELLS
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B Cells
Plasma cells
 B memory cells
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T Cells
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Th cells (T helper cells)
Activated Th cells
 Th memory cells
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Tc cells (Cytotoxic T cells)
Activated Tc cells
 Memory Tc cells
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B CELLS
Have antibodies
(immunoglobulins
) on the surface
 Antibodies are
made of protein
chains and
possess very
specific receptors
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TYPES OF IMMUNOGLOBULINS
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IgA (two molecules)
 Present in milk
 Active against viruses and some bacteria
 Present in tears and saliva
IgD (single molecule)
 Role is unknown
IgE (single molecule)
 Present in allergic reactions
IgG (single molecule)
 Able to cross placenta and present in milk
 Active against viruses and some bacteria
IgM (five molecules)
 Active against some bacteria and viruses
TYPES OF IMMUNOGLOBULINS
B CELLS
Each B cell is specific for one type of antigen (it
only has one type of receptor on its surface)
 Only a few copies of each B cell are created, so
they all have slightly different DNA.
 This allows the immune system to respond to
millions of antigens
 When an antigen enters the body it will quickly
come into contact with the corresponding B cell
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CLONAL-SELECTION THEORY
When a particular B cells comes into contact with
its antigen it quickly multiplies, creating many
clones of itself
 Most of these clones become plasma cells and
release antibodies
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Within a few days (when the infection subsides) the
plasma cells die by apoptosis
Some clones differentiate to become memory cells
to create a long term protection against that
antigen
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This means that if the pathogen strikes again the
immune response will be much more rapid, a greater
number of antibodies are produced during the second
contact
PRIMARY AND SECONDARY
RESPONSES
T CELLS
Cell-mediated immunity
 T helper cells (Th cells) recognise antigens and
stimulate B cells
 Cytotoxic T cells (Tc cells) destroy infected ‘self’
cells
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These cells have foreign antigens on the surface as
well as MHC 1 markers
 The Tc cells recognises the foreign marker and
secretes proteins to lyse the cell
 Tc cells are not effective against free virus particles
 Some Tc cells can also destroy cancerous cells
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TYPES OF BLOOD CELLS
IMMUNITY CELLS
VACCINES
TYPES OF IMMUNITY
Natural

Active immunity
Induced

Receiving the
pathogen and creating
a normal immune
response
 Memory cells created
Receiving
immunisation (aka.
vaccines or antigens)
to create an immune
response
 Memory cells created
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Passive immunity
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Infant receiving
antibodies from the
mother
No memory created
Active immunity
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Passive immunity
Receiving antibodies
from an
injection/serum
 No memory created
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VACCINE
Contain dead or inactive micro-organisms’
 Inactive organisms can be called attenuated, as they
are still able to reproduce but cannot cause disease
 The antigens present in the serum create an
immune response without causing disease
 This leads to a primary response, with memory cells
being produced
 If a vaccinated person comes into contact with the
live pathogen, they will have an immediate and
increased immune response
 Toxoids, inactive toxins, can also be used in vaccines
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ALLERGIES
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Mast cells release histamines creating
contraction in smooth muscles
This decreases the passage of area in the trachea and
bronchi
 Mast cells are found in blood vessels and connective
tissue in the gut and respiratory tract
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Large scale IgE production creates a stronger response,
resulting in anaphylaxis
IgE binds to mast cells to create a response
 IgE is released when ‘sensitive’ antigens are present
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Some people are more sensitive to antigens than others, as
they have antibodies against that particular protein
AUTOIMMUNITY
The immune system fails to recognise ‘self’
proteins
 B and T cells attack and destroy ‘self’ cells
 Examples:
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Systemic Lupus Erythematosus – major organs (esp.
kidney) are not recognised as self
 Multiple sclerosis – the myelin sheath around nerves
is not recognised as self
 Rheumatoid arthritis – joint cartilage is not
recognised as self
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ORGAN TRANSPLANTS
Donor organs must match a certain number of
markers in the recipient
 Biological family members often have a high
number of matches due to similar DNA being
shared
 T helper cells may recognise the grafted organ
and attack it
 Transplant patients must receive drugs to
suppress the action of T cells – eg. Cyclosporin
suppresses T cells, meaning the immune system
is still partially active
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HUMAN BLOOD TYPES
Your blood type is
determined by the
antigens present on your
red blood cells
 O type people can only
receive O type blood, as
they have antibodies
against A-antigens and Bantigens
 AB type people can
receive any type of blood,
because they have no
antibodies against these
antigens
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COMPARISON OF BLOOD TYPE AND
ANTIBODIES
RHESUS FACTOR
The “positive” or
“negative” in blood
types refers to another
protein
 The rhesus protein is
either present
(positive) or absent
(negative)
 Negative blood types
can only receive
negative blood
 This can affect
expectant mothers
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RHESUS FACTOR IN PREGNANCY
If the mother is Rh+ then no problems occur
 If the mother is Rh- problems can arise
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The first Rh+ fetus is unaffected, however at birth
Rh+ blood cells can enter the mother, creating an
immune response (the production of Rh antibodies
 If the mother becomes pregnant to a second Rh+
child, antibodies from the mother may enter the fetus
causing harm
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A Rhesus negative mother can have injections
after birth to remove the fetal blood cells from
her bloodstream, reducing the immune response.
TESTING FOR BLOOD TYPES
Blood is put in 4 wells
 Antibodies are added to
the blood sample wells
 Anti-A is the antibody
for antigen A, Anti-B is
for antigen B and Anti-D
is for the rhesus factor
 Agglutination is
observed as clumping
(indicating the presence
of the antigen)
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PLANT IMMUNITY
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Mechanical barriers
Cuticle or waxy layers
 Cork cells creating galls
 Dropping infected leaves
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Chemical barriers
Release of ‘gum’ to seal off infections
 Oils, acids and other chemical factors
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