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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.
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)
and the
Immunity-Activated
immediately upon
Innate
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.
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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
Defense-Activation 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
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.
Phagocytes and Cell Signaling
•Explain how the previous slide is an example of
cell signaling or cell communication.
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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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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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 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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Created by:
Carol Leibl
Science Content Director
National Math and Science