Download The Innate Immune System

Immune System Part II:
The Innate Immune System
Devastation Caused by Pathogens
•
Influenza epidemic
1918-1919 Killed 22
million people in 18
months.
•
Three million people will
die from malaria this year.
•
Since 1980, over 619,000
people have died from
AIDS in the U.S.
•
Ever seen Contagion?
Overview of the Immune System
Parts of the Immune
System
•Innate Immunity
•Barrier Defenses
•Cellular Response
•Chemical Response
•Adaptive Immunity
•Cell Mediated Response
•Humoral Response
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First Line of Defense
Innate Immunity (Nonspecific Immunity)
Innate Immunity-Activated immediately upon exposure to
pathogen and is the same response for each exposure.
First line of Defense: Integument System•Skin and mucous membranes provide a physical barrier to
entry of pathogens. Skin contains keratin, a structural
protein that helps form that barrier. Mucus helps trap
pathogens.
•Skin's fatty acids and secretion from tears, sweat and oil
glands are toxic to bacteria.
•Natural bacterial fauna can outcompete many pathogen.
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Body Passages and Innate Immunity
•Trachea lined with ciliated cells and
cells that secrete mucus.
•Esophagus leads to stomach with a pH
of 1-2 (acidic) which kills most
pathogens
•Urinary tract has lower pH (again
acidic) and is flushed with urine.
•Tear ducts with lysozymes.
•Reproductive tract also has a lower pH
(acidic once more).
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Second Line of Defense
Phagocytes and the Chemicals Released
•Second Line of DefenseActivation of phagocytes
(leukocytes/white blood
cells)
•Made in the red bone
marrow.
•Found in connective tissue,
tissue lining organs, lymph
nodes and circulating in the
blood.
Neutrophils and Eosinophils
•Neutrophils- are the
first to arrive;
numerous (1 billion
made each day);
survive only a few
days. These are
expendable cells.
•Eosinophils- are weakly phagocytic cells that
kill invaders that are clumped together. They
also destroy parasitic worms.
Basophils and Mast Cells
Basophils and mast cells are leukocytes in nearby
connective tissue which produce histamines which
are released when these cells are damaged.
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Monocytes and Macrophages
Monocytes-are
transformed into
large
macrophages
involved in
phagocytosis and also important
in the adaptive immune response
as an antigen presenting cell.
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Dendritic Cells
King of the Immune System
•Dendritic cells (DC) are
found in skin, nasal passages,
intestines, spleen and throat.
- Population numbers are
smaller than other phagocytes.
Dendritic Cells
•Dendritic cells
are important in
adaptive
immunity as an
antigen
presenting cell
Phagocytes and TLR Receptors
• Phagocytes have Tolllike-receptors (TLR)
which recognize
signature molecules.
• The phagocyte engulfs
the pathogens within a
vesicle and deactivates or
kills the pathogen.
• Phagocytes can eat
themselves to death.
Natural Killer Cell
(not a phagocyte)
•Natural killer cells can
detect infected cells and
cancerous cells due to
changes in plasma
proteins of the cells.
•They secrete chemicals
into the infected cells and
kill them or puncture the
infected cell’s membrane.
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Natural Killer Cells Animation
Phagocytes and Chemical Response
• Phagocytes can
also activate
chemical responses
like the
inflammatory
response and the
production of
antimicrobial
peptides.
Chemical Responses
1. Kinins or chemokines (microbial peptides) are released
by certain phagocytes.
•
These molecules increase circulation and capillary
permeability.
•
Attract leukocytes to site of injury
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Affect nerve cells making area tender
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Complement Proteins
and the Killer Instinct
2. Complement proteins (approx. 30 proteins)
work by a number of different methods.
•These proteins create pores in invading bacteria,
causing water to rush in.
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Complement Proteins
Complement Proteins
Complement Proteins Forming Pores
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Complement Proteins and Opsonizaton
Complement proteins
along with antibodies will
coat a bacterium.
Phagocytes recognize both
the complement proteins
and the antibody.
Phagocytes will engulf the
pathogen and destroy it.
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Interferons
3. Interferons are proteins made by virus-infected cells.
They are secreted and transported to neighboring cells to
prevent viral infection from the infected cell.
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Histamine Release and Inflammatory Response
4. Histamine is released
by mast cells and basophil
cells which are attracted to
an injury site. When the
skin is penetrated, cells
are ruptured releasing
chemical signals to attract
the mast and basophil
cells. These cells release
histamine.
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Inflammatory Response
•Increases capillary
permeability. The area
becomes swollen, red,
temperature increases from the
increased blood flow.
•Phagocytes leave the capillary
bed because they are attracted
histamine and other signals.
•Phagocytes clean up
pathogens and cell debris.
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Homeostasis and Inflammatory Response
•Inflammation continues as long as
the triggers (pathogens) are
present.
•When phagocytes complete their
job by removing the pathogens,
macrophages begin to secrete
substances that•Suppress inflammation
•Promote tissue repair
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Fever
•Inflammatory response is often
accompanied by fever.
•Some cytokines stimulate the brain to
make prostaglandins. These
prostaglandins stimulate the
hypothalamus to a new temperature
set point. The signals the
hypothalamus sends out then:
•Constrict blood vessels in the skin
•Contract skeletal muscles
•Increase heart rate and respiration
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