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IMMUNE SYSTEM
Dr. L. Rueda
CUHS
FIRST SECTION
Animal Defense Mechanisms
Nonspecific Defenses
Physical
Chemical
Inflammatory Response
Cellular
skin and mucous membranes
lysozyme
gastric juice
interferons
complement
histamines
increase blood flow
attract phagocytes
fever
macrophages
neutrophils
eosinophils
natural killer cells
Nonspecific Mechanisms
• They provide general barriers to infection
• 1. The skin and Mucous Membranes: skin is a
physical barrier to microbes helped by oil and
sweat with a low pH. Lysozyme is an enzyme that
attacks bacterial cell walls present in tears, saliva
and mucus.
• 2. Phagocytic White Cells and Natural Killer
Cells.
a. Neutrophils(WBC) are short lived WBC that
phagocytize microbes in infected tissue
Macrophages
b. Monocytes (WBC)
migrate to tissues and
develop into
macrophages, large,
long-lived amoeboid
cells that engulf
microbes and digest
them. Macrophages
may migrate through
the body or become
permanently attached
to lungs, liver, lymph
nodes or spleen. Some
microbes are resistant
to them.
c. Eosinophils (WBC)
attack larger parasitic
invaders with
destructive enzymes.
d. Natural Killer Cells
destroy the body’s
infected or aberrant
cells by attacking their
membranes.
3. Antimicrobial Proteins
a. The complement system is a group of proteins
(about 20) that cooperate with other non-specific
defense mechanisms, resulting in lysis of microbes
or attraction of phagocytes.
b. Interferons are proteins produced by virus
infected cells that diffuse to neighboring cells
stimulating production of proteins that inhibit
viral replication by those cells.
The Complement System
4. The Inflammatory Response
• It is characterized by redness, swelling, and heat.
• Injured cells release chemical signals: basophils in
the blood and mast cells in connective tissue
release histamine, which triggers vasodilation and
leakiness of the blood vessels. WBC release
prostaglandins that promote blood flood to the
injured area.
• A systematic inflammatory response may cause
fever produced by toxins from the microbe or
pyrogens from WBC.
Specific Defenses
Specific Defenses
Humoral
Immunity
B-Cells
produce
antibodies
CellMediated
Helper
T-Cell
Citotoxic T
cells attack
infected or
cancer cells
Active and Passive Immunity
• Active Immunity can be acquired when the
body produces antibodies and develops
immunological memory from either
exposure and recovery from an infectious
disease, or from vaccination with an
inactivated pathogen.
• Passive Immunity: antibodies are supplied
through the placenta to a fetus, to milk to a
nursing infant, or by antibody injection
providing temporal immunity
Active and Passive Immunity
Humoral Immunity
• It involves the production of antibodies that
circulate in the blood and lymph and defend
against free bacteria and viruses.
Cell-Mediated Immunity
• It involves specialized lymphocytes that
react against body cells infected by
microbes. They also response against
transplants and cancerous cells.
• The immune system
mounts specific
attacks against
invaders when
lymphocytes recognize
antigens (components
of foreign molecules)
and produce specific
proteins called
antibodies.
Cells of the Immune System: B cells
• B lymphocytes are
produced and developed
in the stem cells in the
bone marrow.
• B cells have specific
antigen receptors when
activated they produce
plasma cells.
• B cells produce plasma
cells that give raise to
antibodies.
Antibodies
• The “Y” shaped molecule
consists of two pairs of
polypeptide chains: two
identical short chains and
two identical long chains.
• Both chains have a
constant region in the tail
of the “Y” and a variable
region at the ends of the
two arms, the variable
region is specific for
different antigens
Cells of the Immune System: T
Cells
• T cells have antigen
specific receptors.
• They are produced by
stem cells in the bone
marrow and develop in the
thymus.
• Helper T cells stimulate
humoral and cellular
immunity by secreting
cytokines.
• Cytotoxic T cells kill
infected and cancer cells
IMMUNE
RESPONSE
• Microbes attempting to enter
the body must first find a chink
in the body's external
protection. Skin and mucous
membranes are also rich in
scavenger cells and IgA
antibodies. Next, invaders must
elude a series of nonspecific
defenses-those cells and
substances. Many potential
infections are cut short when
microbes are intercepted by
patrolling scavenger cells or
disabled by complement or
other enzymes or chemicals.
Virus-infected cells, for
instance, secrete interferon, a
chemical that rouses natural
killer cells.
Allergy
AIDS
Resources
• http://rex.nci.nih.gov/PATIENTS/INFO_TE
ACHER/bookshelf/NIH_immune/html/imm
35.html