Download The Immune System

The Immune System
(Chapter 15)
The Immune System
• Immunity is the ability to react to antigens
so that the body remains free of disease.
– Disease is a state of homeostatic imbalance.
• Can be due to infection or failure of the immune
system.
Primary Lymphatic Organs
• Lymphatic organs contain
large numbers of
lymphocytes (White Blood
cells).
• Primary organs are:– Red Bone Marrow.
• Site of stem cells.
– Source of B lymphocytes.
– Thymus Gland.
Lymphocytes from bone
marrow pass through to form
T-lymphocytes
• Produces thymic hormones
(thymosin).
• Aids in T lymphocyte
maturation.
Secondary Lymphatic
Organs
• Secondary lymphatic organs are places
where lymphocytes encounter and bind
with antigens.
–
–
–
–
Spleen.
Lymph nodes.
Tonsils.
Peyer’s patches.
Lymphatic Organs
Secondary Lymphatic Organs
• Spleen – upper left of abdominal
cavity behind stomach.
Sectioned off by connective
tissue- white pulp & red pulp.
– White pulp – lymphocytes
– Red pulp – filters blood.
Blood entering the spleen
passes through red pulp
before it leaves (network of
sinuses)
– FRAGILE
Secondary Lymphatic Organs
• Lymph Nodes – occur along
lymphatic vessels. Formed
from connective tissue.
– Packed full of Blymphocytes
– As lymph courses through
sinuses it is filtered by
macrophages, which
engulf pathogens and
debris.
– Also present- Tlymphocytes – fight
infection and attack
cancer cells
Secondary Lymphatic Organs
• Tonsils – patches of
lymphatic tissue.
• Perform the same function
as lymph nodes
– First line of defense
• Peyer’s Patches – on the
intestinal wall and
appendix. Attack pathogens
that ender the body by way
of the intestinal tract.
Nonspecific Defenses
• Barriers to Entry.
– Mucous membranes
• Line respiratory, digestive, and urinary tract.
– Oil gland secretions.
• Chemicals that kill or weaken bacteria on skin
– Ciliated cells.
• Sweep mucus & particles into throat
– Bacteria
• Both in stomach and vagina, prevent pathogens from
gaining a foot-hold.
– Acid
Innate Immunity
• One important function of the immune system is to promote
growth and repair after injury
– Either via physical damage or microorganisms
• The mobilization of innate immune cells to get rid of
damaged cells or microorganisms is called inflammation
• Small molecules called cytokines are also involved
Innate Immunity
• Inflammatory Reaction.
– Tissue damage causes
– tissue cells and mast cells to release chemical mediators.
Innate Immunity
• Inflammatory Reaction.
• Histamine and kinins.
– Capillaries dilate and become more permeable.
» Skin reddens and becomes warm.
– Proteins and fluids escape from tissue. Swelling occurs
Innate Immunity
• Inflammatory Reaction.
– Proteins and fluids escape from tissue and cause swelling.
» Swelling stimulates free nerve endings, causing the
sensation of pain.
Innate Immunity
– Neutrophils and
Monocytes migrate to site
of injury.
– Amoeboid – can change
shape – squeeze through
capillary walls and enter
tissue fluid.
– Neutrophils engulf
pathogens –destroyed by
hydrolytic enzymes when
fused to a lysosome
Innate Immunity
• Macrophages:
Monocytes change into
these as they leave the
blood and enter the
tissues.
– These are phagocytic cells
– Can eat many (100’s) of
pathogens and survive.
– Eat old blood cells and bits
of dead tissue
– Stimulate the immune
response.
• Increase production of white
blood cells in bone marrow
Innate Immunity
• Macrophages:
Monocytes change into
these as they leave the
blood and enter the
tissues.
• Macrophages enter lymph
vessels carring bacteria
fragments to lymph nodes
• This starts a specific
immune response
Protective protein system
• Known as Complement proteins
• Are activated when pathogens enter the body.
• Complement certain immune responses.
Protective protein system
• Attract phagocytes.
• Form holes in bacteria.
• Interferon binds to receptors of non-infected cells causing them
to prepare for possible attack
Specific immunity
• Antigen--shape on cell, allows recognition of self
and detection of foreign cells.
• Antibody--protein that recognizes and binds
antigens.
• Specific defenses respond to antigens.
– Lymphocytes recognize an antigen due to antigen
receptors whose shape allows them to combine with a
specific antigen.
• Immunity is primarily the result of the action of B lymphocytes
and T lymphocytes.
White blood cells
• Granular Leukocytes
– Neutrophils: Most abundant. Have multilobed nucleus.
• They are the first to respond to infection, and engulf pathogens
during phagocytosis.
– Eosinophils: Have bilobed nucleus
• Known to increase in number in the event of parasitic worm
infection and during allergic reaction.
– Basophils: U-shaped or lobed nucleus.
• In connective tissues release histamines along with Mast Cells
White Blood Cells
• Agranular Leukocyles
– Monocyles: Largest of the white blood cells.
• Differentiate into even larger Macrophages
• Phagocytize pathogens, old cells and debris
• Stimulate production of other white blood cells
– Lymphocytes: Two types:
• T-lymphocytes – Destroy any cell with foreign antigens
• B-lymphocytes – Produce antibodies that combine with antigens
–Target pathogens for destruction
Natural Killer Cells
• Natural killer cells kill
virus-infected cells and
tumor cells by cell-to-cell
contact.
– Large, granular
lymphocytes.
T Cells
• Provide cell-mediated immunity.
• Produced in bone marrow, mature in thymus.
• Antigen must be presented in groove of HLA
molecule.
• Cytotoxic T cells destroy non-self protein-bearing
cells.
• Helper T cells secrete cytokines that control the
immune response.
B Cells
• Provide antibody-mediated immunity against
bacteria.
• Produced and mature in bone marrow.
• Reside in spleen and lymph nodes.
– Circulate in blood and lymph.
• Directly recognize antigen and then undergo clonal
selection.
• Clonal expansion produces antibody-secreting
plasma cells and memory B cells.
Clonal selection Theory
• The antigen selects which
lymphocyte will undergo
clonal expansion and produce
more lymphocytes with the
same type of antigen receptor.
– Some become memory
cells – long term immunity
to the same infection.
– B-cells become plasma
cells – fight infection
– Apoptosis – when danger
of infection is over, all
plasma cells undergo
programmed cell death
Specific Defenses
– Antibodies are proteins
shaped like an antigen
receptor and capable of
combining with, and
neutralizing, a specific
antigen.
• Classes.
–
–
–
–
–
Antibodies
IgG - Enhances phagocytosis.
IgM - Activates complement proteins.
IgA - Prevents attachment of pathogens.
IgD - Antigen receptors on virgin B cells.
IgE - Immediate allergic response.
Induced Immunity
• Active Immunity.
– Immunization involves use
of vaccines.
– Contain an antigen to
which the immune system
responds.
– Primary response.
Secondary (booster)
response.
– Dependent upon the
presence of memory B and
T cells capable of
responding to lower
antigen doses.
Induced Immunity
• Passive immunity
• occurs when an individual
is given prepared
antibodies.
– Temporary.
• No memory cells.
• Primary and
secondary injections
Issue - Allergies
• Occurs when your immune system reacts atypically to some
antigens to which the host does not need protection.
• Pollen, dust mites, cats, a hard days work!
– Called Allergens
• The atypical response produces a special antibody
– IgE
• A form of innate immunity
Allergi
esto mast cells.
• IgE binds
•
When a person later
encounters the same allergen,
the allergen binds to the IgE on
the mast cell
• This triggers the explosive
release of histamine
• Capillaries dilate and become
more permeable.
• Skin reddens and becomes
warm. Proteins and fluids
escape from tissue. Swelling
occurs
–
Allergi
es
• The large amounts of
histamines released in an
allergic reaction cause strong
symptoms
• Runny eyes, sneezing, or
shortness of breath
• Depends upon the tissue in
which the mast cells were
triggered
Allergies
• As allergy symptoms are caused by histamines, taking
antihistamines stops the build up of histamines in the cells
of blood vessels.
• However, antihistamines do not stop the immune response
or the release of histamines in mast cells
• Other allergies are mediated by T-cells
– Latex, poison ivy, dyes or chemicals in cosmetics or clothing
– Antihistamines do not help in these allergic reactions
Allergies
• As each allergy is an antigen-specific immune response it
shows memory and a greater response on the next exposure
– This is why allergies get worse over time
• Thousands of different substances can produce allergies in
people – each triggered by a specific antigen-specific
response
– Why people are usually bothered by only a few
• Appears to be inherited
– Remember human genetics and meiosis!!!!
The End.
Any Questions?