Bodys Defenses Im

7/27/2019 Bodys Defenses Im

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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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