Download Chapter 24

Chapter 24
The Immune System 免疫系統
授課教師: 陳炳宏 (生物科技學系)
聯絡方式:
• 辦公室: 第一教學大樓1020/1023室
• 校內分機: 2676
• 電子郵件: [email protected]
• 教學網頁: http://allergy.kmu.edu.tw
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Learning Objectives
Understand:
- how innate defenses help our body act
against infection.
- how acquired immunity plays its role in our
immune responses.
- what common disorders of the immune
system are.
2
An AIDS Uproar
• Acquired immune deficiency syndrome (AIDS)
– Is epidemic throughout much of the world
• Thousands of people are infected every day
3
• HIV, the virus that causes AIDS, attacks the
immune system
– And eventually destroys the body’s ability
to fight infection
4
Innate Defense Against Infection
24.1 Innate defenses against infection include
the skin and mucous membranes, phagocytic
cells, and antimicrobial proteins
• Innate immunity (先天性免疫)
– Is present and effective long before exposure
to pathogens
– 與生俱來。
– 不需要病原菌刺激即存在。
– 反應快速，但持續性低。
– 專一性差，且無記憶性。
5
• Microbes that breach the body’s external
defenses
– Are engulfed and destroyed by
macrophages
Bacteria
6
• An overview of animal immune system
Innate immunity (24.1-3)
Acquired immunity (24.4-15)
Response is the same whether
or not pathogen has been
previously encountered
Found only in vertebrates;
previous exposure to pathogen
enhances immune response
External
barriers
Internal
defenses
• Skin/exoskeleton
• Secretions
• Mucous
membranes
• Phagocytic cells
• NK cells
• Defensive
proteins
• Inflammatory
response (24.2)
•Antibodies (24.8-10)
•Lymphocytes (24.11-14)
The lymphatic system (24.3)
Figure 24.1A
7
• Interferons are proteins produced by virusinfected cells
–
That help other cells resist viruses
Antiviral proteins
block viral
reproduction
Viral nucleic acid
1
2 Interferon
genes
turned
on
New
viruses
DNA
mRNA
3
Interferon
molecules
4
Figure 24.1B
Host cell 1
Makes interferon;
is killed by virus
5
Interferon
stimulates cell to
turn on genes for
antiviral proteins
Host cell 2
Protected against virus by
interferon from cell 1
8
Redness, swelling, heat, pain
24.2 The inflammatory response mobilizes
nonspecific defense forces
• Tissue damage triggers the inflammatory response
Pin
Skin surface
Swelling
Phagocytes
Phagocytes
and fluid move
into area
Bacteria
Chemical
signals
White
blood cell
Blood vessel
1
Tissue injury; release of
chemical signals such as
histamine
Figure 24.2
2
Dilation and increased
leakiness of local blood
vessels; migration of
phagocytes to the area
3
Phagocytes (macrophages
and neutrophils) consume
bacteria and cell debris;
tissue heals
9
• (Puposes) The inflammatory response
– Can disinfect tissues, and
– Can limit further infection from occurring
– Can help heal the damaged tissues
Inflammation
10
24.3 The lymphatic system becomes a crucial
battleground during infection
• The lymphatic system
–
Is a network of lymphatic vessels and organs
Adenoid
Tonsil
Lymph nodes
Thymus
Primary lymphoid
organ
Right lymphatic
duct, entering vein
Thoracic duct,
entering vein
Lymph node
Masses of lymphocytes
and macrophages
Thymus
Adenoid
Secondary lymphoid
organ
Valve
Thoraci
c duct
Lymphatic vessel
Blood capillary
Tissue cells
Appendix
Bone
marrow
Spleen
Interstitial fluid
Lymphatic
vessels
Lymphatic
capillary
Figure 24.3
11
• The vessels collect fluid from body tissues
– And return it as lymph to the blood
• Lymph organs such as the spleen and lymph
nodes
– Are packed with white blood cells that
fight infections
Lymphatic system
= Lymphatic organs + lymphatic vessels + lymph
Circulation system
= Heart + blood vessels + blood
12
Acquired Immunity (獲得性/後天性 免疫)
24.4 The immune response counters specific invaders
• Our immune system
–
Responds to foreign molecules called antigens
(Ags)
• The immune system reacts to antigens
–
And “remembers” an invader
13
• We can temporarily acquire passive immunity
– By receiving “premade” antibodies
• Infection or vaccination
– Triggers active immunity
Figure 24.4
14
24.5 Lymphocytes mount a dual defense
• Two kinds of lymphocytes carry out the immune response
–
B cells secrete antibodies that attack antigens
–
T cells attack cells infected with pathogens
Figure 24.5A
Bone marrow
Bone marrow
- The origin of ALL blood cells.
Thymus
Stem cell
Via
blood
Immature lymphocyte
Antigen
receptors
Humoral
immunity
(B cells)
B cell
Via
blood
T cell
Cell-mediated
immunity
(T cells)
Lymph nodes, spleen,
and other lymphatic
organs
Other parts of the lymphatic
Final maturation of B and
system
T cells in lymphatic organ
15
• Millions of kinds of B cells and T cells, each
with different membrane receptors
– Wait in the lymphatic system, where they
may respond to invaders
Figure 24.5B
16
24.6 Antigens have specific regions where
antibodies bind to them
• Antigenic determinants (‘epitopes’)
– Are the specific regions on an antigen to
which antibodies bind
Antibody A
molecules
Antigenbinding
sites
Antigenic
determinants
Antigen
molecule
Figure 24.6
Antibody B
molecule
17
24.7 Clonal selection musters defensive forces
against specific antigens
• When an antigen enters the body
–
It activates only a small subset of
lymphocytes with complementary
receptors
18
• The selected lymphocyte cells
multiply into clones of shortlived effector cells
– Specialized for
defending against the
antigen that triggered
the response
19
The Steps of Clonal Selection
• In the primary immune response, clonal
selection
– Produces effector cells and memory cells
that may confer lifelong immunity
• In the secondary immune response
– Memory cells are activated by a second
exposure to the same antigen, which
initiates a faster and more massive
response
20
• The primary and secondary immune responses
Primary immune
response
B cells with different
response
Cell activation:
growth, division,
and differentiation
2
1
Antigen receptor
(antibody on cell
surface)
Antigen
molecules
3 First exposure to
antigen
Antibody
4
molecules
5
5
Endoplasmic
reticulum
Plasma (effector) cells secreting antibodies
Secondary immune
response
Figure 24.7A
Antibody
molecules
Antigen
molecules
6
Endoplasmic
reticulum
Clone of memory cells
Second exposure
to the same antigen
Clone of memory cells
Plasma (effector) cells secreting antibodies
21
Primary vs. Secondary Immune Response
•
The primary immune response
–
Is slower than the secondary immune response
Antibody concentration
Second exposure
to antigen X, first
exposure to
antigen Y
Antigen X
First exposure
to antigen X
Primary immune
response to
antigen X
Primary immune
response to
antigen Y
Antibodies
to Y
Antibodies
to X
Figure 24.7B
Secondary immune
response to
0
49
7
56
14
21
28
Time (days)
35
42
22
24.8 Antibodies are the weapons of humoral
immunity
• Antibody molecules
–
Are secreted by plasma (effector) B cells
Figure 24.8A
23
• An antibody molecule
– Has antigen-binding sites specific to the
antigenic determinants that elicited its
secretion
Antigen-binding
sites
Light
chain
Each Ab molecule has 2 antigenbinding sites!!
C
C
Heavy
chain
Figure 24.8B
24
24.9 Antibodies mark antigens for elimination
• Antibodies promote antigen elimination
– Through several mechanisms
Binding of antibodies to antigens
inactivates antigens by
Neutralization
(blocks viral
binding sites;
coats bacteria)
Virus
Agglutination
of microbes
Bacteria
Antigen
molecules
Bacterium
Figure 24.9
Precipitation of
dissolved
antigens
Activation of
Complement
system
Complement
molecule
Foreign
cell
Enhances
Leads to
Phagocytosis
Cell Iysis
Hole
Macrophage
25
CONNECTION
24.10 Monoclonal antibodies are
powerful tools in the lab and clinic
• Monoclonal antibodies
–
Are produced by fusing B cells
specific for a single antigenic
determinant with easy to grow
tumor cells
•
Tumor cell  immortality
•
B cells (speen)  make Abs
Antigen injected
into mouse
Tumor cells
grown in culture
B cells (from
spleen)
Tumor cells
Cells fused to
generate hybrid
cells
Antibody
Single hybrid cell
grown in culture
Hybrid cell culture,
producing monoclonal antibodies
26
• Monoclonal antibodies (mAbs)
– are useful in research, diagnosis, and
treatment of certain cancers
27
24.11 Helper T cells stimulate humoral and cellmediated immunity
• Helper T cells and cytotoxic T cells
–
Are the main effectors of cell-mediated
immunity
• Helper T cells
–
Also stimulate the humoral responses
28
• In cell-mediated immunity, an antigenpresenting cell (APC)
– Displays a foreign antigen and one of the
body’s own self proteins to a helper T cell
29
• The helper T (Th) cell’s receptors (TCR)
–
Recognize the self-nonself complexes and the
interaction activates the helper
T cells
• The helper T cell
–
Can then activate cytotoxic T (Tc) cells and B
cells
30
• The activation of a helper T cell and its roles in
immunity
– Self-nonself complex = MHC + Ag fragment
Self-nonself
complex
B cell
Interleukin-2
stimulates
cell division
T cell
receptor
Microbe
Humoral
Immunity
(secretion of
antibodies by
plasma cells)
Macrophage
3
1
Helper
T cell
2
5
7
4
Self
protein
Antigen from microbe
(nonself molecule)
Figure 24.11
Antigenpresenting cell
Interleukin-1 Binding
site for
stimulates
helper T cell antigen
6
Binding
site for self
protein
Interleukin-2
activates
other B cells
and T cells
Cytotoxic
T cell
Cell-mediated
immunity
(attack on
infected cells)
31
CONNECTION
24.12 HIV destroys helper T cells, compromising the
body’s defenses
• The AIDS virus attacks helper T (Th) Cells
–
Opening the way for opportunistic infection
A human helper T cell (green)
under attach by HIV (red dots).
Figure 24.13
32
24.13 Cytotoxic T (Tc) cells destroy infected body cells
• Cytotoxic T cells
–
Bind to infected body cells and destroy them
1 Cytotoxic T cell binds
to infected cell
Self-nonself
complex
2 Perforin makes holes in
infected cell’s membrane
and enzyme enters
3 Infected cell
is destroyed
Hole
forming
Foreign
antigen
Infecte cell
Perforin
molecule
Cytotoxic
T cell
Enzyme that
can promote
apoptosis
Figure 24.12
33
24.14 Cytotoxic T (Tc) cells may help prevent
cancer
• Cytotoxic T cells may attack cancer cells
– Which have abnormal surface molecules
34
24.15 The immune system depends on our
molecular fingerprints
• The immune system
– Normally reacts only against nonself
substances, not against self
– May reject transplanted organs because
these cells lack the unique “fingerprint” of
the recipient’s self proteins
35
DISORDERS OF THE IMMUNE SYSTEM
CONNECTION
24.16 Malfunction or failure of the immune system causes
disease
• In autoimmune diseases
–
The system turns against the body’s own molecules
• In immunodeficiency diseases
–
Immune components are lacking, and frequent
infections recur
• Physical and emotional stress
–
May weaken the immune system
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Connection
24.17 Allergies are overreactions to certain
environmental antigens
• Allergies
– Are abnormal sensitivities to antigens
(allergens) in the surroundings
37
IgE
Figure 24.17
In mammals, there are 5 Ab types
- IgG, IgM, IgA, IgD, IgE
Summary
- Innate defenses include the skin and mucous membranes,
phagocytic cells, and anti-microbial proteins.
- The inflammation mobilizes nonspecific defense forces.
- The lymphatic system is a crucial system during infection.
- Antigens have specific regions where antibodies can bind.
- Helper T cells help stimulate humoral and cell-mediated
immunity, whereas cytotoxic T cells destroy infected body
cells.
- Allergies are overreactions to certain environmental
antigens.
39
End of Chapter
版權聲明:
1. 本講義所使用之圖片皆由出版商提供或是由網際網路之公開網頁直接下載使用，僅供授課者
上課解說與學生課後複習之教育用途，禁止任何其他商業行為的複製與傳佈。
2. 由網路下載的圖片已盡可能提供原始連結網頁(請直接點選該圖檔)。
3. 本講義之文字或圖片內容若有侵權之虞，歡迎告知授課者，將立即修正相關內容。
40