chapter 23 immune systemimmune system what you’ll learn you will describe how infections are...
TRANSCRIPT
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Chapter 23 Immune System
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What You’ll Learn
You will describe how infections are transmitted and what causes the symptoms of diseases.
You will explain the various types of innate and acquired immune responses.
• You will compare antibody and cellular immunity
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• Section Objectives:
• Describe how pathogens are transmitted.
• Explain what causes the symptoms of a disease.
23.1 Infectious diseases
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What is an infectious disease?
• Disease-producing agents such as bacteria, protozoans, fungi, viruses, and other parasites are called pathogens. (NOT all microorganisms are pathogens
• main sources of pathogens are soil, contaminated water, and infected animals, including other people.
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Reservoirs of pathogens
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Transmission of disease
• Pathogens can be transmitted to a host from reservoirs in four main ways: by direct contact, by an object, through the air, or by an intermediate organism called a vector.
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Transmission of disease II
• The common cold, influenza, and STDs are spread by direct contact.
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Transmission of disease III• Bacteria and other
microorganisms can be present on nonliving objects such as money, toys, or towels.
• Transmission occurs when people unknowingly handle contaminated objects.
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Transmission of disease IV
• Airborne transmission of a disease can occur when a person coughs or sneezes, spreading pathogens contained in droplets of mucus into the air.
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Transmission of disease V• Diseases transmitted by
vectors are most commonly spread by insects and arthropods
• malaria and the West Nile virus are transmitted by mosquitoes.
• Lyme disease and Rocky Mountain spotted fever are diseases that are transmitted by ticks.
• Flies also are significant vectors of disease.
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What causes the symptoms of a disease?
• When a pathogen invades your body, it encounters your immune system.
• If the pathogen overcomes the defenses of your immune system, it can metabolize and multiply, causing damage to the tissues it has invaded, and even killing host cells
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Damage to the host by viruses and bacteria
• Most of the damage done to host cells by bacteria is inflicted by toxins.
• These poisons can inhibit protein synthesis in the host cell, destroy blood cells and blood vessels, produce fever, or cause spasms by disrupting the nervous system.
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Patterns of Diseases
• Some diseases, such as typhoid fever, occur only occasionally in the United States.
• On the other hand, many diseases are constantly present in the population-endemic disease. Ex. Common cold
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Treating Diseases
• 1 way: An antibiotic is a substance produced by a microorganism that, in small amounts, will kill or inhibit the growth and reproduction of bacteria.
• Your body also has its own built-in defense system— the immune system —that works to keep you healthy.
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• Section Objectives:• Identify the cells, tissues, and organs that
make up the immune system.
• Compare innate( nonspecific) and acquired (specific)immune responses.
• Distinguish between antibody and cellular immunity.
• Summarize the structure of the lymphatic system
• Distiguish between passive and active immunity
23.2 The Immune System
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Lines of defense• 1st line:– broad, external defense
• “walls & moats” – skin & mucus membranes
• 2nd line:– broad, internal defense
• “patrolling soldiers”– phagocyte (eating) WBCs
• 3rd line:– specific, acquired immunity
• “elite trained units”– lymphocyte WBCs & antibodies
• B & T cells
Barriers
Non-specific patrol
Immune system
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Innate Immunity
• The body’s earliest lines of defense against any and all pathogens make up your nonspecific, innate immunity.
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Nonspecific defense I• 1st line of defense:• Skin Intact skin is a
formidable physical barrier to the entrance of microorganisms
• Body secretions mucus traps many microorganisms
• Sweat, tears, and saliva all contain the enzyme lysozyme, which is capable of breaking down the cell walls of some bacteria
Lining of trachea: ciliated cells & mucus secreting cells
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Nonspecific defense II• 2nd line of defense • Inflammation(Inflammatory response) characterized by
four symptoms—redness, swelling, pain, and heat; histamine released causes blood vessels in the injured area to dilate,(redness) which makes them more permeable to tissue fluid. Fluid that leaks from the vessels helps the body destroy toxic agents and restore homeostasis (swelling and pain,&heat)
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Nonspecific defense V• After a few days, infected
tissue harbors a collection of live and dead white blood cells, multiplying and dead pathogens, and body fluids called pus.
• Pus formation usually continues until the
infection subsides.
• Eventually, the pus is cleared away by macrophages.
PusPhagocytes
Swelling
occurs
Tissue fluid moves
into injured area
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Nonspecific defense III• 2nd line of defensePhagocytosis of
pathogens white blood cells that destroy pathogens by surrounding and engulfing them.
• Macrophages are white blood cells that provide the first defense against pathogens that have managed to enter the tissues.
Macrophage “eating” bacteria
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Phagocytes
yeastmacrophage
macrophage
bacteriawhite blood cells that eat
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Fever
• When a local response is not enough– full body response to infection– raises body temperature – higher temperature helps in defense• slows growth of germs• helps macrophages• speeds up repair of tissues
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Nonspecific defense IV
• Phagocytosis of pathogens• If the infection is not stopped by the tissue
macrophages, another type of phagocyte, called a neutrophil is attracted to the site.
• If the infection is not stopped by tissue macrophages and neutrophils -
Monocytes
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Nonspecific defense VI
• Protective proteins:• Interferons are proteins that protect cells
from viruses.
• Complement: help attract phagocytes to foreign cells and help destroy foreign cells
• Natural Killer cells:type of white blood cell that destroy the body's own infected cells, may attack cells that form tumors
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The lymphatic system
• The lymphatic system becomes a crucial battleground during infection
• a network of lymphatic vessels and organs– It returns tissue fluid to the
circulatory system– It fights infections
• Lymph nodes are key sites for fighting infection– They are packed with
lymphocytes and macrophages
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Acquired Immunity
• Defending against a specific pathogen by gradually building up a resistance to it
• This acquired immune response enables these white blood cells to inactivate or destroy the pathogen.
• Acquired immunity involves the production of two kinds of immune responses: antibody immunity and cellular immunity ~
• your 3rd line of defense
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Acquired Immunity
• SPECIFIC IMMUNITY• IMMUNE RESPONSE a recognition system that distinguishes “self” from
“non-self”• responds to foreign molecules called antigens• Stimulates the body to make antibodies: specific defensive proteins which help to counter
antigens in various ways
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How are invaders recognized?• Antigens– chemical name tags on the surface of
every cell• “self” vs. “invader”
disease-causingbacteria
disease-causingvirus
one of yourown cells
antigens say:“I belong here”
antigens say:“I am an invader”
antigens say:“I am an invader”
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3rd line of defenseLymphocytes ~type of white blood cell that carry
out the immune response• Two kinds– B cells secrete antibodies
that attack antigens (antibody immunity)
– T cells attack cells infected with pathogens (cellular immunity)
B lymphocyte
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B cells & antibodies• B cells– white blood cells that attack
invaders in blood– mature in Bone marrow
• Patrolling B cells – make antibodies against invader immediately
• Memory B cells– remembers invader– can make antibodies quickly the next time• protects you from getting disease more than once
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• Proteins made by B cells that tag invaders in the blood so macrophages can eat them– tag says “this is an invader” gotcha!
• biological “handcuffs”– antibody attaches to antigen of invader
Antibodies
macrophageeating tagged invaders
invading germs tagged with antibodies
Y
Y
YY
YY
Y
B cells releasing antibodies
Y
YY
Y
Y
Y
Y
Y Y
Y
Y
Y
Y
Y
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Antibody Immunity
• An antibody molecule has antigen-binding sites specific to the antigen
• Do not posses the power to destroy antigens directly, tag and mark them for destruction by a variety of mechanisms
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B cells immune responseinvader(foreign antigen)
Y
Y
Y
Y
B cellsY
Y
Y
Y
Y
YY
Y
Y
Y
Y
Y
Y
Y
Y
YY
Y
Y
Y
Y
Y
Y
YY
Y
Y
Y
“reserves”
memory B cells
Y
Y
Y
Y
Y
YY
YY
YY
Y
Y
B cellsrelease antibodiespatrol bloodforever
recognition
10 to 17 days
YY
Y
Y
YY Y
YY
Y
Y
Y
Y
YY
YYY
YYY
Y
Y
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T cells• T cells mature in Thymus• Helper T cells – sound the alarm for rest
of immune system
• Killer T cells– destroy infected body cells
• Memory T cells– remembers invader & reacts against
it again quicklyWhere’s that?
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Attack of the Killer T cells• Killer T cells destroy infected body cells– T cell binds to invaded cell– secretes perforating protein• punctures cell membrane of infected cell• cell bursts
Perforin puncturescell membrane
cell membrane
Killer T cell
cell membrane
invaded cell
vesicle
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2006-2007
What if the attacker gets past the B cells in the blood &
infects some of your cells?You need trained assassins to kill
off these infected cells!
T
Attackof the Killer T cells!
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Cellular Immunity
Pathogen
engulfed by
MacrophageDisplays antigens
on surface and
stimulates T cell
Helper T cell
Stimulates
Cytotoxic T cell
Attacks infected
cell
Cytotoxic T cell
Foreign
antigen
Infected cells
Perforin
Infected cell lyses
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Immune responseinvader
invaders in blood invaders infect cells
B cells T cells
macrophages
helperT cells
patrollingB cells
memoryB cells
memoryT cells
killerT cells
YYY
Y
YY
Y
YantibodiesY
Y Y
skinskininvaders in body
YY
Y
Y
YY
Y
YantibodiesY
Y Y
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Passive and Active Immunity
• Acquired immunity to a disease may be either passive or active.
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Passive Immunity
Passive: short term, antibodies passed on, not stimulated by antigens,
acquired naturally by placenta or breast milk or
artificially acquired by a shot
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Active Immunity
1. Active: long term, conferred by actual encounter with infection (naturally acquired) or vaccination *(artificially acquired)
* vaccine~ substance consisting of weakened, dead, ,or parts of pathogen or antigen that when injected , stimulates the immune system
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23.3 Noninfectious disorders
Section objective:•Describe categories od noninfectious disease
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Noninfectious disorders
Genetic disorders•Caused by the inheritance of genes that do not function properly• ex: sickle cell anemia, hemophilia, cystic fibrosis
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Noninfectious disorders
• Degenerative diseases~ result of a part of the body wearing out ex: degenerative arthritis
• Metabolic diseases~ results in an error in a biochemical pathway
• Cancer~ abnormal cell growth
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DISORDERS OF THE IMMUNE SYSTEM
• Allergies are overreactions to certain environmental antigens called
allergens : Ex. Animal dander, dust mites, pollen
release of histamine causes symptoms: sneezing, increased mucus production in the nasal passages, and redness.
Antihistamines can relieve symptoms
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DISORDERS OF THE IMMUNE SYSTEM
• Autoimmune diseases
immune system also can mistakenly attack the body’s own tissues – Examples: Rheumatic
fever, Type I Diabetes, Multiple Sclerosis, Rheumatoid arthritis, Lupus
Rheumatoid arthritisRheumatoid arthritis
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DISORDERS OF THE IMMUNE SYSTEM
• Immunodeficiency diseases– Immune components
are lacking, and infections recur
Ex: Acquired immune deficiency syndrome (AIDS)
SCIDS
HIV on a lymphocyte
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AIDS
– HIV (Human Immunodeficiency Virus) the virus that causes AIDS
– HIV is transmitted mainly in blood and semen
– HIV kills helper T-cells and leads to AIDS
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Attacking transplanted tissue.
• T cells and antibodies also can attack transplanted tissue, such as a transplanted kidney, that comes from a source outside the body.