Transcript BCBio12_Chapter10_immunity

UNIT B: Human Body Systems
Chapter 8: Human Organization
Chapter 9: Digestive System
Chapter 10: Circulatory System and
Lymphatic System: Section 10.7
Chapter 11: Respiratory System
Chapter 12: Nervous System
Chapter 13: Urinary System
Chapter 14: Reproductive System
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Chapter 10: Circulatory System and Lymphatic System
Chapter 10: Circulatory System and Lymphatic System
In this chapter, you will learn
about the structure and
function of the circulatory
system and lymphatic
system.
In 2013, Lance Armstrong confessed to long-term blood
doping and the use of banned substances. Blood doping
involves artificially boosting the blood’s ability to bring
more oxygen to muscles. Aerobic capacity and
endurance improve where there are additional red blood
cells available to carry oxygen.
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What is the composition of
blood, including blood cells?
What organs and structures
control the flow of blood
throughout the body?
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
10.7 Innate and Adaptive Immunity
The lymphatic system works with the immune system to
protect the body from pathogens, toxins, and other invaders.
Immunity is a condition where the body is protected from
various threats (pathogens, toxins, cancer cells). There are
two main types of immunity.
• Innate immunity: Fully functional without previous
exposure to substances
• Adaptive immunity: Initiated and amplified after specific
recognition of substances
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Innate Immunity
Mechanisms of innate immunity can be divided into at least
four types:
•
•
•
•
Physical and chemical barriers
Inflammatory response
Phagocytes and natural killer cells
Protective proteins
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Physical and Chemical Barriers
Physical barriers
• Skin and mucous membranes lining the respiratory, digestive,
and urinary tracts are physical barriers to pathogens
Chemical barriers
• Oil glands in the skin secrete chemicals that weaken or kill
certain bacteria
• The acidic pH of the stomach kills many types of bacteria or
inhibits their growth
• Bacteria that reside in the intestine and other areas remove
nutrients and block binding sites that could be used by pathogens
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Inflammatory Response
Inflammatory response
• A series of events that is initiated when there is damage to
tissues by physical trauma, chemical agents, or pathogens
• Inflamed areas have four signs: redness, heat, swelling, pain
o Mostly due to capillary changes in the damaged area
• At least three types of cells in the skin and connective tissue
play a role in the inflammatory response:
o Mast cells
o Macrophages
o Dendritic cells
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Chapter 10: Circulatory System and Lymphatic System
Figure 10.23 Inflammatory response. Due to capillary changes in a
damaged area and the release of chemical mediators, such as histamine by
mast cells, an inflamed area exhibits redness, heat, swelling, and pain. The
inflammatory reaction can be accompanied by other reactions to the injury.
Macrophages and dendritic cells, present in the tissues, phagocytize
pathogens, as do neutrophils, which squeeze through capillary walls from the
blood. Macrophages and dendritic cells release cytokines, which stimulate the
inflammatory and other immune reactions. A blood clot can form to seal a
break in a blood vessel.
Section 10.7
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Inflammatory Response
Mast cells
• Reside in the skin, lungs, and intestinal tract
• Respond to damage by releasing histamine
o Histamine causes capillaries in the area to dilate and
become more permeable, allowing fluids to escape to
tissues and cause swelling
o Swollen area stimulates free nerve endings, causing pain
o Increased blood flow causes skin to redden and warm
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Inflammatory Response
Macrophages and Dendritic Cells
• Both are phagocytic cells
• Release various proinflammatory cytokines, which are
chemical messengers that influence other immune cells
o Interleukin-8: attracts other immune cells to the scene
o Colony-stimulating factor: causes bone marrow to
produce more white blood cells
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Phagocytes and Natural Killer Cells
Phagocytes
• Engulf pathogens into an endocytic vesicle, which fuses with
a lysosome in the cell; pathogen is destroyed by compounds
in the lysosome
• Includes neutrophils and monocytes
o Neutrophils: the first white blood cells to enter an
inflamed area; may accumulate to form pus
o Monocytes: migrate from blood and differentiate into
macrophages in tissues if inflammatory reaction
continues
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Phagocytes and Natural Killer Cells
Natural killer (NK) cells
• Large, granular cells that kill some virus-infected and cancer
cells by cell-to-cell contact
• NK cells induce target cells to undergo apoptosis
o Seek out and kill cells that lack a type of “self” molecule,
called MHC-I (major histocompatibility class I), on their
surface
o Some virus-infected and cancer cells lack MHC-I, which
makes them susceptible to destruction by NK cells
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Adaptive Immunity
Adaptive immunity is activated when innate defences fail
to prevent an infection.
The adaptive immune system recognizes, responds to, and
usually eliminates antigens from the body.
• Antigens: any molecules that stimulate an adaptive
immune response
• Adaptive defences take 5 to 7 days to become fully
activated and last for many years
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
The adaptive immune system depends on the activity of B
cells and T cells.
• Both cells recognize antigens because they have specific
antigen receptors
• Each lymphocyte has only one type of receptor
• Large diversity of antigen receptors on B and T cells
o There are specific B cells and/or T cells for almost
any possible antigen
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
B Cells and Antibody-Mediated Immunity
Defence by B cells (antibody-mediated immunity)
• B cells are activated in a lymph node or the spleen, when their
receptors bind to specific antigens
• Cytokines secreted by T cells stimulate B cells to divide
o Most cells become plasma cells, which secrete antibodies
− Antibodies are the secreted form of the receptor of the
B cell that was activated
o Some cells become memory B cells, which allow for longterm immunity
− If the same antigen enters again, memory B cells divide
and give rise to more plasma cells that can produce the
antibody against the antigen
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
B Cells and Antibody-Mediated Immunity
Antibody Structure
• Antibodies are also called immunoglobulins (Ig), which are
Y-shaped molecules with two arms made of polypeptides
o Heavy (long) polypeptide chain
o Light (short) polypeptide chain
o C (constant) region: set sequence of amino acids
o V (variable) region: amino acid sequence varies between
antibodies; forms the antigen-binding site
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Chapter 10: Circulatory System and Lymphatic System
Figure 10.24 Structure of an
antibody.
a. An antibody contains two
heavy (long) polypeptide
chains and two light (short)
chains arranged so that there
are two variable regions, where
a particular antigen is capable
of binding with an antibody (V =
variable region, C = constant
region). The shape of the
antigen fits the shape of the
binding site.
b. Computer model of an
antibody molecule. The antigen
combines with the two side
branches.
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Section 10.7
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
B Cells and Antibody-Mediated Immunity
• Antigens combine with an antibody at the antigen-binding site
in a lock-and-key manner
• Antigen-antibody reactions can result in immune complexes
(antigens combined with antibodies)
o Immune complexes may mark the antigens for destruction
by a neutrophil or macrophage
o Antibodies can “neutralize” toxins by preventing them from
binding to cells
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
T Cells and Cell-Mediated Immunity
Defence by T cells (cell-mediated immunity)
• T cells have a unique T-cell receptor but cannot recognize
antigens on their own
o Require antigens be “presented” to the receptors by an
MHC (major histocompatibility complex) protein
on the surface of another cell
• There are two types of T cells:
o Helper T cells (TH cells)
o Cytotoxic T cells (TC cells or CTLs)
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
T Cells and Cell-Mediated Immunity
Helper T cells (TH cells)
• Only recognize antigens presented by specialized antigenpresenting cells (APCs) with MHC class II proteins on their
surface
Cytotoxic T cells (TC cells or CTLs)
• Only recognize antigens presented by various cells with MHC
class I proteins on their surface
• Some T cells become memory T cells
o Live for many years and can quickly initiate immune
response to an antigen previously present in the body
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Chapter 10: Circulatory System and Lymphatic System
T Cells and Cell-Mediated Immunity
Cell-mediated immunity by TC cells
• Activated TC cells bound to a
virus-infected or cancer cell
release perforin, which forms
pores in the plasma membranes
of the abnormal cell
o This allows enzymes called
granzymes to enter the target
cell and induce apoptosis
Figure 10.25 Cell-mediated immunity.
a. How a TC cell destroys a virusinfected cell or cancer cell.
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Section 10.7
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Chapter 10: Circulatory System and Lymphatic System
T Cells and Cell-Mediated Immunity
• TC cells are capable of
moving on to kill other
target cells
Figure 10.25 Cell-mediated
immunity. b. The scanning
electron micrograph shows
cytotoxic T cells attacking and
destroying a cancer cell
(target cell).
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Section 10.7
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
Check Your Progress
1. Name one physical and one chemical barrier to infection.
2. List the four cardinal signs of inflammation, and explain why
each one occurs.
3. Contrast the way that macrophages typically kill pathogens
with the method used by natural killer cells.
4. Compare the specific functions of helper T cells and
cytotoxic T cells.
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7
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Chapter 10: Circulatory System and Lymphatic System
Section 10.7