what is immunity?

8/14/2019 What is Immunity?

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ImmunityImmunity


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Immunity

What is immunity?What is immunity?

Immunity is the body's ability to fight offImmunity is the body's ability to fight offharmful micro-organisms PATHOGENS-harmful micro-organisms PATHOGENS-that invade it.that invade it.

The immune system produces antibodiesThe immune system produces antibodiesor cells that can deactivate pathogens.or cells that can deactivate pathogens.

Fungi, protozoans, bacteria, and virusesFungi, protozoans, bacteria, and virusesare all potential pathogens.are all potential pathogens.


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What advantage do pathogensWhat advantage do pathogens

have over humans?have over humans?

All have a short life span andAll have a short life span and

reproductive time.reproductive time.

So what?So what?


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What is an infectious disease?What is an infectious disease?

AnAninfectious diseaseinfectious disease is one in whichis one in which

minute organisms, invisible to theminute organisms, invisible to the

naked eye, invade and multiplynaked eye, invade and multiply

within the body.within the body.

Many of these organisms areMany of these organisms arecontagiouscontagious,, that is they spreadthat is they spread

between people in close contact.between people in close contact.


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The first person to identify microbesThe first person to identify microbes

as causing disease wasas causing disease was Robert KochRobert Koch..

We still useWe still use Kochs PostulatesKochs Postulates inin

disease identification.disease identification.


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Kochs PostulatesKochs Postulates

1.1. Pathogen must be found in the host inPathogen must be found in the host in

every case.every case.

2.2. Pathogen must be isolated from the hostPathogen must be isolated from the host

and grown in pure culture.and grown in pure culture.

3.3. When placed in a healthy host, pathogenWhen placed in a healthy host, pathogen

produced in pure culture must cause theproduced in pure culture must cause the

disease in the host.disease in the host.

4.4. Pathogen must be isolated from the newPathogen must be isolated from the new

host and shown to be the originalhost and shown to be the original

pathogen.pathogen.


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Endemic diseasesEndemic diseases are those found normallyare those found normally

in a population.in a population.

For example.For example.


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AnAnepidemic diseaseepidemic disease is a disease that manyis a disease that many

people acquire over a short period of time.people acquire over a short period of time.

For exampleFor example


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AApandemic diseasepandemic disease is a world-wideis a world-wide

epidemic disease.epidemic disease.

For example.For example.


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AnAn antibioticantibiotic is a chemical substanceis a chemical substance

derivable from a mold or bacteriumderivable from a mold or bacterium

that kills microorganisms and curesthat kills microorganisms and curesinfectionsinfections..


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The Immune SystemThe Immune System - includes all- includes allparts of the body that help in theparts of the body that help in the

recognition and destruction ofrecognition and destruction of

foreign materials. White blood cells,foreign materials. White blood cells,phagocytes and lymphocytes, bonephagocytes and lymphocytes, bone

marrow, lymph nodes, tonsils,marrow, lymph nodes, tonsils,

thymus, and your spleen are all partthymus, and your spleen are all part

of the immune system.of the immune system.


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First-Line DefensesFirst-Line Defenses //Innate ImmuneInnate ImmuneSystemSystem-- The body's first line of defenseThe body's first line of defenseagainst pathogens uses mostly physicalagainst pathogens uses mostly physical

and chemical barriers such asand chemical barriers such as Skin acts as a barrier to invasionSkin acts as a barrier to invasion Sweat has chemicals which can killSweat has chemicals which can kill

different pathogens.different pathogens.Tears - have lysozyme which has powerfulTears - have lysozyme which has powerful

digestive abilities that render antigensdigestive abilities that render antigensharmless.harmless.

Saliva also has lysozyme.Saliva also has lysozyme. Mucus - can trap pathogens, which are thenMucus - can trap pathogens, which are then

sneezed, coughed, washed away, orsneezed, coughed, washed away, ordestroyed by chemicals.destroyed by chemicals.

Stomach Acid destroys pathogensStomach Acid destroys pathogens


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Second-Line DefensesSecond-Line Defenses- If a pathogen- If a pathogen

is able to get past the body's first lineis able to get past the body's first line

of defense, and an infection starts, theof defense, and an infection starts, thebody can rely on it's second line ofbody can rely on it's second line of

defense. This will result in what isdefense. This will result in what is

called an.called an.

fl


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Inflammatory responseInflammatory responsecausescauses

Redness - due to capillary dilationRedness - due to capillary dilation

resulting in increased blood flowresulting in increased blood flow

Heat - due to capillary dilation resulting inHeat - due to capillary dilation resulting in

increased blood flowincreased blood flow

Swelling due to passage of plasma fromSwelling due to passage of plasma from

the blood stream into the damaged tissuethe blood stream into the damaged tissue

Pain due mainly to tissue destructionPain due mainly to tissue destruction

and, to a lesser extent, swelling.and, to a lesser extent, swelling.


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Third-Line DefensesThird-Line Defenses -- Sometimes the secondSometimes the secondline of defense is still not enough and theline of defense is still not enough and thepathogen is then heading for the body's lastpathogen is then heading for the body's lastline of defense, theline of defense, the immune systemimmune system..

TheThe immune systemimmune system recognizes, attacks,recognizes, attacks,destroys, and remembers each pathogen thatdestroys, and remembers each pathogen thatenters the body. It does this by makingenters the body. It does this by making

specialized cells and antibodies that render thespecialized cells and antibodies that render thepathogens harmless.pathogens harmless.

Unlike the first line and second line defense theUnlike the first line and second line defense the

immune system differentiates amongimmune system differentiates amongpathogens.pathogens.

For each type of pathogen, the immune systemFor each type of pathogen, the immune systemproduces cells that are specific for thatproduces cells that are specific for that

particular pathogen.particular pathogen.


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AntigensAntigens can enter the body from the environment.can enter the body from the environment.

These includeThese include

inhaled macromolecules (e.g., proteins on cat hairsinhaled macromolecules (e.g., proteins on cat hairs

that can trigger an attack ofthat can trigger an attack ofasthmaasthma in susceptiblein susceptible

people)people)

ingested macromolecules (e.g., shellfish proteinsingested macromolecules (e.g., shellfish proteins

that trigger anthat trigger an allergic responseallergic response in susceptiblein susceptible

people)people)

molecules that are introduced beneath the skinmolecules that are introduced beneath the skin

(e.g., on a splinter or in an injected(e.g., on a splinter or in an injected vaccinevaccine))
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antigens can be generated within theantigens can be generated within the

cells of the body. These includecells of the body. These include

proteins encoded by the genes ofproteins encoded by the genes of

viruses that have infected a cellviruses that have infected a cell

aberrant proteins that are encodedaberrant proteins that are encoded

by mutant genes; such as mutatedby mutant genes; such as mutated

genes in cancer cellsgenes in cancer cells


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LymphLymph is a milky body fluid that containsis a milky body fluid that containsa type of white blood cells, calleda type of white blood cells, calledlymphocyteslymphocytes, along with proteins and fats., along with proteins and fats.

LymphLymph seeps outside the blood vessels inseeps outside the blood vessels in

spaces of body tissues and is stored in thespaces of body tissues and is stored in thelymphatic systemlymphatic system to flow back into theto flow back into thebloodstream.bloodstream.


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Through the flow of blood in and out of arteries, andThrough the flow of blood in and out of arteries, and

into the veins, and through theinto the veins, and through the lymph nodeslymph nodes and intoand into

thethe lymphlymph, the body is able to eliminate the products of, the body is able to eliminate the products of

cellular breakdown and bacterial invasion.cellular breakdown and bacterial invasion.


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There are more thanThere are more than 100 tiny, oval100 tiny, oval

structures calledstructures calledlymph nodeslymph nodes. These. These

are mainly in the neck, groin andare mainly in the neck, groin and

armpits, but are scattered all alongarmpits, but are scattered all along

the lymph vessels.the lymph vessels.

They act as barriers to infection byThey act as barriers to infection by

filtering out and destroying toxins andfiltering out and destroying toxins and

germs. The largest body of lymphoidgerms. The largest body of lymphoidtissue in the human body is thetissue in the human body is the

spleen.spleen.


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As theAs the lymphlymph flows through lymphflows through lymphvessels, it passes throughvessels, it passes through lymph nodeslymph nodes..

White blood cells calledWhite blood cells called macrophagesmacrophagestrap and engulf cell debris andtrap and engulf cell debris andpathogenspathogens. Other white blood cells, called. Other white blood cells, called

LymphocytesLymphocytes -- are a type of white bloodare a type of white bloodcell capable of producing acell capable of producing aspecific immune responsespecific immune response to uniqueto unique

antigens. Theyantigens. They produceproduce antibodiesantibodies whichwhichare chemicals that mark pathogens forare chemicals that mark pathogens fordestruction.destruction.
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The scanning electron micrograph above, shows a

human macrophage (gray) approaching a chain ofStreptococcus pyogenes (yellow). Riding atop themacrophage is a spherical lymphocyte. Bothmacrophages and lymphocytes can be found nearan infection, and the interaction between thesecells is important in eliminating infection.


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Once a white cell has left the blood vessel andOnce a white cell has left the blood vessel and

migrated to the enemy, the next job is to EAT themigrated to the enemy, the next job is to EAT the

microbe.microbe.

TheThe macrophagemacrophage is a large phagocyte. Ais a large phagocyte. A

phagocytephagocyteis an eating cell (phago = "eating",is an eating cell (phago = "eating",

cyte = "cell") which engulfs invaders.cyte = "cell") which engulfs invaders.


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Immunity is the result of the action of two types lymphocytes,Immunity is the result of the action of two types lymphocytes,thetheB lymphocytesB lymphocytes and theand theT lymphocytesT lymphocytes..

B cells produce antibodies that are secreted into the blood andB cells produce antibodies that are secreted into the blood andlymph.lymph.

T cells attack the cells that have antigens that they recognize.T cells attack the cells that have antigens that they recognize.

Killer T Cells (lymphocytes) recognize surface


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Killer T Cells (lymphocytes) recognize surfacemarkers on other cells labeled for destruction.

They, Killer T Cells, help to keep virus-infected

or malignant cells in check.

Here, a smaller Killer T Cell (arrow) is attackingand killing a much larger flu virus-infected

target. The sequence represents 30 minuteselapsed time.


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It has been estimated that during our lifetime,It has been estimated that during our lifetime,we will encounter a million foreign antigenswe will encounter a million foreign antigenscapable of causing disease, and our bodiescapable of causing disease, and our bodies

need the same amount of lymphocytes toneed the same amount of lymphocytes todefend against them.defend against them.

There will always be aThere will always be a different type ofdifferent type of

lymphocyte for each possible antigenlymphocyte for each possible antigen..


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Active Immunityoccurs when when

one makes his/her own antibodies. This

type of immunity is long term.

Getting the disease : If you get aninfectious disease (like Chicken Pox),

often times, that stimulates theproduction of MEMORY cells whichare then stored to prevent theinfection in the future.

injection of a weakened form of the


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injection of a weakened form of theactual antigen that causes thedisease. The injection is too weak to

make you sick, but your Blymphocytes will recognize theantigen and react as if it were the

"real thing". Thus, you produceMEMORY cells for long termimmunity.

Passive Immunity occurs when the


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Passive Immunityoccurs when theantibodies come from some other source.

This type of immunity is short term.

Breastmilk : Milkfrom a mother'sbreast contains

antibodies. Thebaby is acquiringpassive immunity.These antibodies

will only lastseveral weeks.


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Gamma Globulin: A Gamma Globulin shot is

purely an injection of antibodies to provide

temporary immunity. You might receive anGamma Globulin shot if you travel outside of

the country.

what is immunity?

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