Download Immune Notes 1 - Little Miami Schools

Anatomy & Physiology
Chapter
24: Immune System
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-The immune system protects
against external and internal
assaults on the body
-Immune system patrols and
protects the body
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-Antigens are unique molecules
recognized by the immune system that
mark cells, viruses, etc.
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 Self markers—identifying YOUR cells as “self”
 Nonself markers—molecules on the surface of
foreign cells that identify it as foreign
-Self-tolerance—the ability of our
immune system to attack abnormal or
foreign cells but spare our own normal
cells
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-Innate immunity (nonspecific) provides a
general defense against all kinds of
pathogens (anything not “self”)
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- present at birth (innate)
- Cells involved in innate immunity:
Epithelial barrier cells, neutrophils,
macrophages, and Natural Killer cells
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-Adaptive immunity (specific) acts as a
defense that recognizes and responds
to specific threatening agents
-Cells involved in adaptive immunity
- - lymphocytes called T cells and B
cells
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-Species resistance—genetic characteristics of
a species (like Homo sapiens) innately defend
against certain pathogens
 our bodies are not suitable for certain
pathogens that affect other animals
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- Internal body is protected by a barrier:
skin and mucous membranes
- -Sebum- contains pathogen inhibiting
agents
- -Mucus- pathogens can get stuck in it and
swept away
- -Enzymes- can hydrolyze pathogens
- -HCl in stomach- can destroy pathogens
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Second line of defense- Inflammation and fever
 -Inflammatory response—tissue damage elicits
responses to counteract injury
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-Chemicals released: histamine, kinins,
prostaglandins, etc.
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 Chemotactic factors—substances that attract
white blood cells to area of injury in a process
called chemotaxis
-Heat, redness, pain, and swelling caused by
increased blood flow and vascular permeability
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-Fever—abnormally high body
temperature triggered by
inflammation mediators:
prostaglandins
 -Triggered in SIRS (systemic
inflammatory response
syndrome) and other events such
as viral infections, tumors,
allergies
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Prostaglandins released into blood  brain
 Tell hypothalamus to reset body’s set
point temperature
Our bodies heat up to achieve this new target
We shiver (chills) to help heat up
105 and above is dangerous  potential
denaturation of proteins leading to death
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Fever is thought to increase immune
function and inhibit pathogens
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Phagocytosis—ingestion and
destruction of microorganisms or
other small particles by phagocytes
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-Neutrophil—most numerous phagocyte;
usually first to arrive at site of injury;
migrates out of bloodstream, forms pus
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Macrophage—large
phagocytic monocyte cells
that grow to several times
original size after migrating
out of bloodstream;
important APCs
Dendritic cells- found in
skin and mucous, have
long branches or
extensions
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Natural killer (NK) cells —lymphocytes
(WBC) that kill tumor cells and cells
infected by viruses
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- Made in Red Bone Marrow
- Method of killing cells —lysing cells by
damaging plasma membranes
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Notes 2
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Part of the third line of defense
consisting of lymphocytes
2 types: B lymphocytes (B cells) and T
lymphocytes (T cells)
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-B-cells- produce antibodies that attack
pathogens
-T cells- attack pathogens more directly
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-Effector cell: a B or T cell that is actively
producing an immune response
-Memory cell: a B or T cell that has been
activated but is not an effector cell;
rather survives in lymph nodes and
produces immune response if exposed
to antigen again
-Naïve: B or T cell that has never been
exposed to a specific antigen (inactive)
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-Development of B cells
1. B cells are developed in yolk sac and
red bone marrow (throughout life)=
Naïve B cells
2. Naïve B cells synthesize antibodies in
membrane
3. Naïve B cells are activated when they
are exposed to an antigen
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4. Binding to antigen triggers rapid
mitosis- one B-cell produces clone
(family) of identical B-cells
5. Effector B cells and memory B cells
formed
 Effector B cells- produce 1000s of identical
antibodies
 Memory B cells- remain in lymphatic tissue
until activated by future antigen exposure
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-Antibodies= proteins of
immunoglobulin (Ig) family
-Babies are born with different clones
of B cells in bone marrow, lymph
nodes, and spleen
-B cells all synthesize a DIFFERENT
specific antibody
-Huge antibody diversity: “genetic
lottery”- 10 billion possibilities
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-Functions of antibodies
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1.Recognize antigens and bind to antigenbinding sites- blocks them from invading
healthy cells
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2.Transforms toxic antigens into harmless
substances
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Antibodies
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3.Agglutinates antigens to make
disposal by phagocytes more rapid
4.Binding alters the shape of antibody
molecule to expose binding sitesattracts other cells to phagocytize
pathogen
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1.Primary response—initial
encounter with a specific antigen
triggers the formation and release
of specific antibodies that reaches
its peak in a few days
vaccination
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Primary and Secondary response
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2.Secondary response—a later encounter
with the same antigen triggers a much
quicker response; B memory cells rapidly
divide, producing more plasma cells and
thus more antibodies
Booster shot
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Vaccine and booster shot
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T Cells are lymphocytes (WBCs) that go
through the thymus gland 1st
Activated when an antigen binds to its
receptors
Causes clone of T cells
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Effector and memory T cells
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Cytotoxic T cells= Killer T cells
Helper T cells—stimulate B cells, T cells,
phagocytes
Suppressor T cells—regulatory T cells
that suppress lymphocyte function, thus
regulating immunity and reducing T cell
reactions to self-antigens
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Functions of T cells
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T cells defend us from viruses and cancer,
but also cause rejection of transplanted
organs
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Adaptive or acquired immunity=
resistance developed after birth
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Natural immunity results from
nondeliberate exposure to antigens
Artificial immunity results from
deliberate exposure to antigens, called
immunization/vaccination
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Types of Adaptive Immunity
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Active immunity: immune system responds
to exposure to harmful agent
Passive immunity: immunity in one individual
is transferred to another individual
◦ Antibodies in mother’s milk pass immunity to
nursing infant
◦ Temporary but immediate protection
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