The Immune System Chapter 24 - Davis School · PDF filefight infections Copyright © 2005...
Transcript of The Immune System Chapter 24 - Davis School · PDF filefight infections Copyright © 2005...
1
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The Immune System
Chapter 24
Bacteria
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
An AIDS Uproar• Acquired immune deficiency syndrome (AIDS)
– Is epidemic throughout much of the world
• Thousands of people are infected every day
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• HIV, the virus that causes AIDS, attacks the immune system
– And eventually destroys the body’s ability to fight infection
2
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
INNATE DEFENSES AGAINST INFECTION
24.1
• Innate immunity
– Is present and effective long before exposure to pathogens
– Innate defenses against infection
• Surface barriers
– skin
– mucous membranes
• Nonspecific response
– phagocytic cells
– antimicrobial proteins
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Microbes that breach the body’s external defenses
– Are engulfed and destroyed by macrophages
Figure 24.1A
Bacteria
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
New viruses
����Host cell 1Makes interferon; is killed by virus
4����Host cell 2
Protected against virus by interferon from cell 1
• Interferons are proteins produced by virus-infected cells
– That help other cells resist viruses
2 Interferon genesturnedon
mRNA
3
Interferon molecules
DNA
1
Viral nucleic acidAntiviral proteins block viral reproduction
Interferon stimulates cell to turn on genes for antiviral proteins
5
Figure 24.1B
3
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Complement system
Group of 30 plasma proteins
• Circulate in blood
• Trigger lysis of invading cells
• Help trigger specific and nonspecific immune response
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
DEFENSE MECHANISMS
4
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
White blood cell role in the inflammatory response
Neutrophils:
phagocytize bacteria
Eosinophils:
secrete enzymes that punch holes in bacteria
Basophils:
Secretes histamine
Macrophages:
engulf and digest most any antigens
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.2 The inflammatory response mobilizes nonspecific defense forces
• Tissue damage triggers the inflammatory response
Pin�� Skin surface
Bacteria
Chemical signals
White blood cell
1 Tissue injury; release of chemical signals such as histamine
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
Swelling
Phagocytes and fluid move into area
Phagocytes
Blood vessel
Figure 24.2
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The inflammatory response
– Can disinfect tissues and limit further infection
– Localized warming and redness occurs
– Macrophages secrete interleukins• Communication w/other WBCs
• Signal fever
5
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.3 The lymphatic system Is a network of lymphatic vessels and organs
Figure 24.3
Adenoid
Tonsil
Lymph nodes
Right lymphatic duct, entering vein
Thymus
Appendix
Thoracic duct
Bone marrow
Lymphatic vessels
Spleen
Thoracic duct, entering vein
Lymph node
Masses of lymphocytes and macrophages
Valve
Lymphatic vessel
Blood capillary
Tissue cells
Interstitial fluid
Lymphatic capillary
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Vessels collect fluid from body tissues– return it as lymph to the blood
• spleen and lymph nodes– Are packed with white blood cells that
fight infections
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Adenoid
Tonsil
Lymph nodes
Right lymphatic duct, entering vein
Thymus
Appendix
Thoracic duct
Bone marrow
Lymphatic vessels
Spleen
Thoracic duct, entering vein
Lymph node
Masses of lymphocytes and macrophages
Valve
Lymphatic vessel
Blood capillary
Tissue cells
Interstitial fluid
Lymphatic capillary
6
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.4 The immune response counters specific invaders
• Immune system – Responds to antigens
• Any molecule that causes an immune response
– And “remembers” antigen as an invader• Chicken pox
ACQUIRED IMMUNITY: develops after exposure to pathogen
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Active immunity:
• own immune system produces antibodies
– Infection or vaccination
Passive immunity
• receive “premade” antibodies
– Triggers active immunity
Figure 24.4
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.5 Lymphocytes carry out immune responseTwo kinds of lymphocytes
– B cells secrete antibodies that attack antigens– T cells attack cells infected with pathogens
Bone marrow Thymus
Stem cell
Immature lymphocyte
B cellHumoral immunity
Via blood
Antigenreceptors
Via blood
T cellCell-mediated immunity
Lymph nodes, spleen, and other lymphatic organs
Final maturation of B and T cells in lymphatic organ
Other parts of the lymphatic system
Figure 24.5A
7
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• 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
– Dual Defense• Humoral immunity
– Against bacteria and viruses free in the blood or interstitial fluid
– B cells• Cell-mediated
– Against bacteria and viruses inside body cells, fungi, protozoans, and cancer cells
– T cellsFigure 24.5B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.7 Clonal selection
•PRIMARY IMMUNE RESPONSE
• First time against a specific antigen
– antigen enters the body
– It activates a small subset of lymphocytes with specific receptors to that antigen
– Activated lymphocyte cells multiply into clones
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Clonal Selection• The primary immune response, produces
– effector cells• Combat the antigen, short lived
– memory cells• lifelong immunity
• In the secondary immune response– Second exposure to antigen
• Memory cells activited
• Faster response
8
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The primary and secondary immune responses
Primary immuneresponse
B cells with differentresponse
Cell activation:growth, division,and differentiation
Antibodymolecules
Plasma (effector) cells secreting antibodies
Endoplasmicreticulum
Clone of memory cells
Antigen receptor(antibody on cellsurface)
Antigenmolecules
2
First exposureantigen
3
4
1
5
5
Antigenmolecules
6 Second exposureto same antigen
Antibodymolecules
Endoplasmicreticulum
Plasma (effector) cells secreting antibodies Clone of memory cells
Secondary immuneresponse
Figure 24.7A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Second exposure to antigen X, first
exposure to antigen Y
First exposure to antigen X
Primary immune response to antigen X
Primary immune response to antigen Y
Antibodies to Y
Antibodies to X
Ant
ibod
y co
ncen
tratio
n
0 7 14 21 28 35 42 49 56
Time (days)
Secondary immune response to antigen
X
Figure 24.7B
Primary vs. Secondary Immune Response• The primary immune response
– Is slower than the secondary immune response
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.8 Antibodies are the weapons of humoral immunity
• Antibody molecules
– Produced by effector B cells
• Bind to antigen
• Assist in elimination of antigen
Figure 24.8A
9
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• An antibody molecule
– Specific antigen-binding
Figure 24.8B
Light chain
Heavy chain
CC
Antigen-binding sites
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Antibody elimination mechanismsNeutralization
physically blocks harmful antigens
Agglutination
clumps groups of cells together for phagocytosis
Precipitation of dissolved antigens
link dissolved antigen molecules together
Activates complement proteins
attach to foreign cells causing lysis
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Binding of antibodies to antigens inactivates antigens by
Neutralization(blocks viral binding sites;
coats bacteria) Agglutination of microbes
Precipitation of dissolved antigens
Activation of Complement system
Cell IysisPhagocytosis
Virus
Bacterium
Bacteria
Antigen molecules
Complement molecule
Foreign cell Hole
Macrophage
Enhances Leads to
24.9 Antibodies mark antigens for elimination
Figure 24.9
10
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.11 Helper T cells stimulate humoral and cell-mediated immunity
1. Macrophage ingests a microbe
2. Macrophage becomes antigen presenting cell by placing part of the antigen on its membrane by its MHC
3. Helper T cell recognize and bind to the self-nonself complex on the antigen presenting cell
• Receptors on each helper T cell can bind only ONE kind of self-nonself complex on the antigen presenting cell
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Humoral Immunity
B cells divide
Memory B cells
Effector B cells
-Make antibodies
VS Cell-Mediated Response
Cytotoxic T cells Divide
Memory T cells
active cytotoxic T cells
-target infected body cells
4. Antigen presenting cell releases interleukin-1●stimulates the helper T cell
5. Activated helper T cells ●Divide to produce memory and
more helper T cells●Secrete interleukin-2 which
activates B cells and Cytotoxic T cells
11
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Figure 24.11
MicrobeMacrophage
Antigen from microbe (nonself molecule)
1
Self protein
23
4
5 6
7
Antigen-presenting cell
Interleukin-1 stimulates helper T cell
HelperT cell
Interleukin-2stimulatescell division
Interleukin-2activatesother B cells and T cells
HumoralImmunity(secretion of antibodies by plasma cells)
Cytotoxic T cell
Cell-mediated immunity (attack on infected cells)
Binding site for antigen
Binding site for self protein
B cellSelf-nonselfcomplex T cell
receptor
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Humoral Immunity
(Antibody mediated response)
12
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.12 HIV destroys helper T cells, compromising the body’s defenses
• The AIDS virus attacks helper T Cells
– Opening the way for opportunistic infection
CONNECTION
Figure 24.12
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
3 Infected cellis destroyed
1 Cytotoxic T cell bindsto infected cell
2 Perforin makes holes ininfected cell’s membraneand enzyme entersSelf-nonself
complex
Infecte cell
CytotoxicT cell
Perforinmolecule
Foreignantigen
Enzyme thatcan promoteapoptosis
Holeforming
Figure 24.13
24.13 Cell Mediated Response
– Cytotoxic T
• Bind to infected body cells and destroy them
13
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
24.14 Cytotoxic T cells may help prevent cancer
• Cytotoxic T cells may attack cancer cells
– Which have abnormal surface molecules
Figure 24.14
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
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
14
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
DISORDERS OF THE IMMUNE SYSTEM CONNECTION24.16 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
24.17 Allergies are overreactions to certain environmental antigens
• Allergies
– Are abnormal sensitivities to antigens (allergens) in the surroundings
CONNECTION
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The two stages of an allergic reaction
Figure 24.17
B cell(plasma cell)
Antigenic determinant
1 Allergen (pollen grain)enters blood stream
2 B cells makeantibodies
3 Antibodiesattach tomast cell
Sensitization: Initial exposure to allergen
Mast cell
Histamine
4 Allergen binds toantibodies onmast cell
5 Histamine isreleased, causingallergy symptoms
Later exposure to same allergen
3 Antibodiesattach tomast cell