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Topic 6: Human Physiology
Topic 6.3
Defense against the
infectious disease
Fighting the
Enemy Within! phagocyticleukocyte
lymphocytes
attacking
cancer cell
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Why an immune system?
Attack from outside lots of organisms want you for lunch!
animals are a tasty nutrient- & vitamin-packed meal cells are packages of macromolecules
no cell wall
traded mobility for susceptibility
animals must defend themselves against invaders
viruses
HIV, flu, cold, measles, chicken pox, SARS
bacteria
pneumonia, meningitis, tuberculosis
fungi yeast (Athletes foot)
protists
amoeba, Lyme disease, malaria
Attack from inside
defend against abnormal body cells = cancers
Mmmmm,Whats in your
lunchbox?
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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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Lymph systemProduction & transport of leukocytes
Traps foreign invaders
lymph node
lymph vessels(intertwined amongst blood vessels)
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Lines of defense 1 1st line: Barriers
broad, external defense walls & moats
skin & mucus membranes
2nd line: Non-specific patrol
broad, internal defense patrolling soldiers
leukocytes = phagocytic WBC macrophages
3rd line: Immune system specific, acquired immunity
elite trained units
lymphocytes & antibodies
B cells & T cells
Bacteria & insectsinherit resistance.
Vertebrates
acquire immunity!
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Lines of Defense 2
Nonspecific Defense Mechanisms
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1st line: External defense
Physical & chemicaldefenses
non-specific defense
external barrier epithelial cells & mucus
membranes
skin respiratory system
digestive system
uro-genital tract Lining of trachea:
ciliated cells & mucussecreting cells
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1st line: Chemical barriers onepithelium
Skin & mucous membrane secretions sweat
pH 3-5
tears
washing action mucus traps microbes
saliva anti-bacterial = lick your wounds
stomach acid pH 2
anti-microbial proteins lysozyme enzyme
digests bacterial cell walls
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2nd line: Internal, broad range patrol
leukocytesleukocytes Innate, general defense rapid response
Patrolling cells & proteins
attack invaders that penetratebodys outer
barriers
leukocytes
phagocytic white blood cells
complement system
anti-microbial proteins
inflammatory response
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Leukocytes: Phagocytic WBCs
Attracted by chemicalsignals released by damaged cells enter infected tissue, engulf & ingest microbes
lysosomes
Neutrophils most abundant WBC (~70%)
~ 3 day lifespan
Macrophages big eater, long-lived
Natural Killer Cells destroy virus-infected cells
& cancer cells
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Phagocytic and Natural Killer Cells Neutrophils
60-70% WBCs; engulf anddestroy microbes at infected tissue
Monocytes
5% WBCs; develop into.
Macrophages
enzymatically
destroy microbes
Eosinophils
1.5% WBCs; destroy largeparasitic invaders (blood flukes)
Natural killer (NK) cells
destroy virus-infected body
cells & abnormal cells
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Phagocytes
yeastmacrophage
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Natural Killer Cells perforate cells release perforin protein
insert into membrane of target cell
forms pore allowing fluid toflow into cell
cell ruptures (lysis)
apoptosis
Destroying cells gone bad!
perforin
punctures
cell membrane
cellmembrane
natural killer cell
cellmembrane
virus-infected cell
vesicle
perforin
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Anti-microbial proteins
Complement system ~20 proteins circulating in blood plasma
attack bacterial & fungal cells
form a membrane attack complex perforate target cell
apoptosis
plasma membrane ofinvading microbe
complement proteinsform cellular lesion
extracellular fluid
complement proteins
bacterial cell
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Inflammatory response 1
Damage to tissue triggers localnon-specific inflammatory
response release histamines & prostaglandins
capillaries dilate,more permeable (leaky)
increase blood supply
delivers WBC, RBC, platelets, clotting
factors
fight pathogens clot formation
accounts for swelling, redness & heat
of inflammation & infection
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Inflammatory response 2
Bacteria
Blood vessel
Chemicalalarm signals
Pin or splinterBlood clot
Phagocytes
swelling
Reaction to tissue damage
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Fever
When a local response is not enough systemic response to infection
activated macrophages release interleukin-1 (IL-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
of iron to grow
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The Inflammatory Response 1- Tissue injury; release of chemical signals~
histamine (basophils/mast cells): causes Step 2... prostaglandins: increases blood flow & vessel permeability
2/3- Dilation and increased permeability of capillary~
chemokines: secreted by blood vessel endothelial cells
mediates phagocytotic migration of WBCs
4- Phagocytosis of pathogens~ fever & pyrogens: leukocyte-released molecules increase body
temperature
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Specific defense lymphocytes
B lymphocytes (B cells)
T lymphocytes (T cells)
antibodies immunoglobulins
Responds to
antigens specific pathogens
specific toxins
abnormal body cells
(cancer)
3rd line: Acquired (active) Immunity
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self foreign
How are invaders recognized: antigens
Antigens proteins that serve as cellular name tags foreign antigens cause response from WBCs
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
pathogens in blood & lymph
T cells recognize antigen fragments
pathogens which have already infected cells
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How are cells tagged with antigens Major histocompatibility (MHC) proteins
antigen glycoproteins
MHC I on all nucleated cells
MHC II on macrophages, B-Ly, activated T-Ly
MHC proteins constantly carry bits of cellular
material from the cytosol to the cell surface snapshot of what is going on inside cell
give the surface of cells a unique label or fingerprint
MHC proteins
displaying self-antigens
T cell
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Specific Immunity
Lymphocyctespluripotent stem cells...
B Cells (bone marrow) T Cells (thymus)
Antibodies:antigen-bindingimmunoglobulin, produced by Bcells
Antigen = a foreign moleculethat elicits a response bylymphocytes (virus, bacteria,
fungus, protozoa, parasitic worms)
Antigen receptors =plasmamembrane receptors on B and Tcells
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What else well study? HIV & AIDS
Human Immunodeficiency Virus virus infects helper T cells
helper T cells dont activate rest of immunesystem: T cells & B cells
also destroy T cells
Acquired ImmunoDeficiency Syndrome infections by opportunistic
diseases death usually from other
infections pneumonia, cancer
T
Attack!Its too late
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Animals are a tasty nutrient- &vitamin-packed meal !
Whats thepoint?
To defendthemselves
against invaders!
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HIV/AIDS - How to protect
yourself
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Immune system malfunctions Auto-immune diseases
immune system attacks own molecules & cells lupus
antibodies against many molecules released by normalbreakdown 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, dust mites, in animal
saliva
stimulates release of histamine
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Key attributes of immune
system
4 attributes that characterize theimmune 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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Its safe
to Ask Questions!
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Ghost of Lectures past
(storage)
T
Did I miss a joke?
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Abnormal immune function Allergies (anaphylactic shock): hypersensitive responses to environmental
antigens (allergens); causes dilation and blood vessel permeability(antihistamines); epinephrine
Autoimmune disease: multiple sclerosis, lupus, rheumatoid arthritis,
insulin-dependent diabetes mellitus
Immunodeficiency disease: SCIDS (bubble-boy); A.I.D.S.
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Induction of Immune Responses Primary immune response:lymphocyte proliferation and
differentiation the 1st time the body is exposed to an antigen Plasma cells: antibody-producing effector B-cells
Secondary immune response: immune response if the individual
is exposed to the same antigen at some later time~ Immunological
memory
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