Transcript Ch48Immunity - Environmental

phagocytic
leukocyte
“Fighting the
Enemy Within”
Immune System
Chapter 51
AP Biology
lymphocytes
attacking
cancer cell
lymph
system
2006-2007
Avenues of attack
 Points of entry
digestive system
 respiratory system
 urogenital tract
 break in skin

 Routes of attack
circulatory system
 lymph system

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Why an immune system?
 Attack from outside


lots of organisms want you for lunch!
animals must defend themselves against
unwelcome invaders
 viruses
 bacteria

All in a
good day’s
work!
protists
 fungi

we are a tasty vitamin-packed meal
 cells are packages of macromolecules
 no cell wall
 traded mobility for susceptibility
 Attack from inside

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defend against abnormal body cells = cancers
Lines of defense
 1st line: Barriers

broad, external defense
 “walls & moats”

skin & mucus membranes
 2nd line: Non-specific patrol

broad, internal defense
 “patrolling soldiers”

leukocytes (phagocytic WBCs)
 3rd line: Immune system

specific, acquired immunity
 “elite trained units”

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lymphocytes & antibodies
1st: External defense
 non-specific defense
 external barrier

epithelial cells &
mucus membranes
 skin
 respiratory system
 digestive system
 genito-urinary tract
Lining of trachea:
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ciliated cells & mucus
secreting cells
1st: Chemical barriers on epithelium
 Skin & mucous membrane secretions

sweat
 pH 3-5

tears
 washing action

mucus
 traps microbes

saliva
 anti-bacterial = “lick your wounds”

stomach acid
 pH 2

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anti-microbial proteins
 lysozyme
 digests bacterial cell walls
2nd: Internal, broad range patrol
leukocytes
 innate defense
 rapid response
 cells & proteins

attack invaders that
penetrate body’s outer
barriers
 leukocytes
 phagocytic white blood cells
 anti-microbial proteins
 inflammatory response
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Leukocytes: Phagocytic WBCs
 Neutrophils
attracted by chemical signals released
by damaged cells
 enter infected tissue, engulf & ingest
microbes

 amoeba-like (fierce!)
 digest via lysosomes
 ~3 day life span
 Macrophages
“big eater”
 bigger, long-lived
phagocytes
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
Phagocytes
macrophage
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yeast
Lymph system
Production & transport of leukocytes
Traps foreign invaders
lymph vessels
(intertwined amongst blood vessels)
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lymph node
Development of Red & White blood cells
inflammatory
response
Red blood cells
fight
parasites
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develop into
macrophages
short-lived phagocytes
60-70% WBC
Inflammatory response
 Damage to tissue triggers
local inflammatory
response


release histamines &
prostaglandins
capillaries dilate,
more permeable
 increase blood supply
 delivers WBC, RBC, platelets,
clotting factors
 lead to clot formation
 swelling, redness & heat of
inflammation & infection
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Inflammatory response
 Reaction to tissue damage
Pin or splinter
Blood clot
swelling
Bacteria
Chemical
alarm signals
Phagocytes
Blood vessel
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Fever
 When a local response is not enough

systemic response to infection

activated macrophages release interleukin-1
 triggers hypothalamus in brain to readjust body
thermostat to raise body temperature

higher temperature helps defense
 inhibits bacterial growth
 stimulates phagocytosis
 speeds up repair of tissues
 causes liver & spleen to store
iron reducing blood iron levels
 bacteria need large amounts
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of iron to grow
3rd: Acquired Immunity
 Specific defense

lymphocytes
 B lymphocytes (B cells)
 T lymphocytes (T cells)

antibodies
 immunoglobulins
 Responds to…

antigens
 specific microorganisms
 specific toxins
 abnormal body cells
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Antigens
 Proteins that serve as cellular name tags


foreign antigens cause response from WBCs
proteins belonging to:
 viruses, bacteria, protozoa, parasitic worms, fungi, toxins
 non-pathogens: pollen & transplanted tissue
 B cells & T cells respond to different antigens

B cells recognize intact antigens
 invaders in blood & lymph

T cells recognize antigen fragments
 invaders which have infected cells
“self”
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“foreign”
Lymphocytes
 B cells


mature in bone marrow
humoral response system
 “humors” = body fluids
 produce antibodies
 T cells


mature in thymus
cellular response system
 Learn to distinguish
“self” from “non-self”
antigens during maturation
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B cells
 Humoral response = “in fluid”

defense against attackers circulating freely
in blood & lymph
 Specific response

produces antibodies against
specific antigen
 tagging protein = immunogloblin
 millions of different B cells,
each produces different antibodies,
each recognizes a different antigen

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types of B cells
 plasma cells
 immediate production of antibodies
 short term release
 memory cells
 long term immunity
Y
 “this is foreign!”
variable
binding region
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multi-chain proteins produced by B cells
antibodies match molecular shape of antigens
immune system has antibodies to respond to
millions of antigens (invaders)
tagging system
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 Proteins that bind to a specific antigen
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Antibodies
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each B cell
has ~100,000
antigen receptors
How antibodies work
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10 to 17 days for full response
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release antibodies
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plasma cells
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recognition
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captured
invaders
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memory cells
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B cells + antibodies
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tested by
B cells
(in blood & lymph)
invader
(foreign antigen)
“reserves”
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B cell immune response
clone
1000s of clone cells
1° vs 2° response to disease
 Memory B cells allow a rapid, amplified
response with future exposure to pathogen
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How can we
have so many
antibody
proteins &
so few genes?
Variable region
Antibody
Constant region
Light chain
B cell
Heavy chain
Variable DNA
combinations:
Transcription
of gene
• 1M different B cells
• 10M different T cells
mRNA
DNA of
differentiated
B cell
C
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Rearrangement
of DNA
V
40 genes for
Variable region
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Chromosome
of undifferentiated B cell
Vaccinations
 Active immunity

immune system exposed to
harmless version of pathogen
 Stimulates immune system to produce
antibodies to invader

rapid response if
future exposure
 Most successful
against viral diseases
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1914 – 1995
Jonas Salk
 Developed first vaccine

against polio
April 12, 1955
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Polio epidemics
1994:
Americas polio free
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Passive immunity
 Maternal immunity
antibodies pass from mother to baby
across placenta or in breast milk
 critical role of breastfeeding in infant
health

 mother is creating antibodies against
pathogens baby is being exposed to
 Injection
injection of antibodies
 short-term immunity

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T cells
 Immune response to infected cells

defense against invaders inside
infected cells
 viruses & bacteria within infected cells,
fungi, protozoa & parasitic worms

defense against “non-self” cells
 cancer & transplant cells
 Kinds of T cells

helper T cells
 stimulate immune system

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killer T cells
 attack infected body cells
How are cells tagged with antigens
 Glycoproteins on surface of cells have
unique “fingerprint”
major histocompatibility proteins (MHC)
 human leukocyte antigens (HLA)

 MHC proteins constantly export bits of
cellular protein to cell surface

“snapshot” of what is
going on inside cell
T cell
MHC proteins
displaying self-antigens
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How do T cells know a cell is infected
 Infected cells digest some pathogens &
export pieces to MHC proteins on cell
surface

invading
pathogen
antigen presenting cells (APC)
MHC proteins
displaying
foreign antigens
T cell
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T cell antigen
receptors
T cell response
infected cell
helper
T cell
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helper
T cell
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stimulate
B cells &
antibodies
Y
activated
macrophage
Y
or
helper
T cell
helper
T cell
Y
interleukin 1
activate
killer T cells
Y
helper
T cell
killer
T cell
Attack of the Killer T cells
 Destroys infected body cells
binds to target cell
 secretes perforin protein

 punctures cell membrane of infected cell
Killer T cell
Killer T cell
binds to
infected
cell
Vesicle
Cell
membrane
Perforin
punctures
cell membrane
Cell
membrane
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Infected cell
destroyed
Target cell
Immune response
pathogen invasion
antigen
exposure
free antigens in blood
humoral response
macrophages
cellular response
B cells
helper
T cells
T cells
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Y antibodies
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memory
B cells
Y
plasma
B cells
Y
antigens on infected cells
memory
T cells
cytotoxic
T cells
HIV & AIDS
 Human Immunodeficiency Virus
virus infects helper T cells
 helper T cells don’t activate rest of
immune system: T cells & B cells

 also destroy T cells
 Acquired ImmunoDeficiency Syndrome
infections by opportunistic
diseases
 death usually from other
infections

 pneumonia or cancer
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Immune system malfunctions
 Auto-immune diseases

immune system attacks own molecules & cells
 lupus
 antibodies against many molecules released by normal
breakdown of cells
 rheumatoid arthritis
 antibodies causing damage to cartilage & bone
 diabetes
 beta-islet cells of pancreas attacked & destroyed
 multiple sclerosis
 T cells attack myelin sheath of brain & spinal cord nerves
 Allergies

over-reaction to environmental antigens
 allergens = proteins on pollen, from dust mites, in
animal saliva
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Key attributes of immune system
 4 attributes that characterize the
immune system as a whole

specificity
 antigen-antibody specificity

diversity
 react to millions of antigens

memory
 rapid 2° response

ability to distinguish self vs. non-self
 maturation & training process to reduce
auto-immune disease
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Any Questions??
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2006-2007