Immune SystemImmune System

A Boo Boo lets in germsA Boo Boo lets in germs

Like…BacteriaLike…Bacteria

Or a virusOr a virus

A germ is still a germ….A germ is still a germ….

1.1. PathogenPathogen=agent that causes disease=agent that causes disease

22. Antigen. Antigen= foreign particle that triggers = foreign particle that triggers an an

immune responseimmune response

- often they are proteins - often they are proteins on on the surface of viruses the surface of viruses and and bacteria bacteria

Your Body’s Defenses Your Body’s Defenses AgainstAgainstDiseaseDisease

Nonspecific Defenses: Attack all Nonspecific Defenses: Attack all pathogens and antigens the same pathogens and antigens the same wayway

Specific Defenses: Immune Response Specific Defenses: Immune Response – Attack pathogens that get past the – Attack pathogens that get past the nonspecific defenses nonspecific defenses

Nonspecific DefensesNonspecific Defenses

This means that the identity This means that the identity of the pathogen/antigen is of the pathogen/antigen is not not importantimportant. The response is . The response is the same if a bacteria, virus, the same if a bacteria, virus, splinter or bullet invades the splinter or bullet invades the body.body.

Nonspecific DefensesNonspecific DefensesFirst Line DefensesFirst Line Defenses

Skin: Forms a physical barrier to pathogensSkin: Forms a physical barrier to pathogens-oils and sweat make skin acidic – -oils and sweat make skin acidic –

inhibits inhibits the growth of pathogens the growth of pathogens -lysozyme-enzyme found in sweat and -lysozyme-enzyme found in sweat and

tears tears digests bacterial cell walls digests bacterial cell walls Mucus Membranes-layers of tissue which Mucus Membranes-layers of tissue which

secrete mucussecrete mucus - found in body openings and the - found in body openings and the

respiratoryrespiratory systemsystem - mucus traps pathogens - mucus traps pathogens

Nonspecific DefensesNonspecific DefensesSecond Line DefensesSecond Line Defenses Inflammatory ResponseInflammatory Response

Damaged cells release histamines – chemical cry for helpDamaged cells release histamines – chemical cry for help

- histamines cause blood vessels to dilate (open) bringing - histamines cause blood vessels to dilate (open) bringing

blood to the area.blood to the area.

- the dilated blood vessels become leaky releasing fluid and white - the dilated blood vessels become leaky releasing fluid and white blood cells in the infected areablood cells in the infected area

- causes swelling and redness in the damaged area- causes swelling and redness in the damaged area

- pus – fluid and dead cells forms- pus – fluid and dead cells forms White Blood cells White Blood cells

- Macrophages – - Macrophages – “Big Eaters” engulf and kill pathogens“Big Eaters” engulf and kill pathogens

- Neutrophils-- Neutrophils-engulf bactera and release chemicals that engulf bactera and release chemicals that kill the bacteria and themselves. kill the bacteria and themselves.

-- Natural Killer Cells –Natural Killer Cells – recognize and kill virus infected recognize and kill virus infected

cells and tumorscells and tumors

Textbook page 925Textbook page 925

Histamines are released Blood vessels dilateHistamines are released Blood vessels dilate

and leak and leak

MacrophageMacrophage

Nonspecific DefensesNonspecific DefensesSecond Line Defenses (continued)Second Line Defenses (continued)

Temperature Response - Temperature Response - Fever – Fever –

-Body temp increases in response to infection-Body temp increases in response to infection

-pathogenic bacteria don’t grow well at higher temp-pathogenic bacteria don’t grow well at higher temp

ProteinsProteins - - Complement Proteins: Complement Proteins: kill pathogens by punching a kill pathogens by punching a hole hole

in the cell membranein the cell membrane

- Intrerferon: - Intrerferon: a protein released by cells infected by virusesa protein released by cells infected by viruses

-causes nearby cells to release an enzyme preventing the virus -causes nearby cells to release an enzyme preventing the virus

from reproducingfrom reproducing

Fevers help eliminate Fevers help eliminate pathogenspathogens

Specific DefensesSpecific Defenses

Third Line of DefenseThird Line of Defense

Specific DefensesSpecific Defenses

- identity of pathogen/- identity of pathogen/

antigen must be knownantigen must be known

- the specific immune - the specific immune

response is tailored to response is tailored to

the specific pathogenthe specific pathogen

Specific DefensesSpecific DefensesMacrophage Links Nonspecific to Macrophage Links Nonspecific to

SpecificSpecific

When a macrophage engulfs a When a macrophage engulfs a pathogen, it displays the viral pathogen, it displays the viral antigen on its surfaceantigen on its surface

The antigen is joined to a MHC (Major Histocompatibility Complex)

The MHC is a protein on the surface ofall vertebrate cells

The anitgen must be bound to the MHC for the Helper T Cell to recognize it

Specific DefensesSpecific DefensesHelper T CellsHelper T Cells

Receptor proteins on helper T cells (TReceptor proteins on helper T cells (THH) )

bind to viral antigens displayed on the bind to viral antigens displayed on the macrophagemacrophage

causes macrophage tocauses macrophage to release Interleukin1release Interleukin1

Interleukin1 activates Interleukin1 activates

the helper T cells (Tthe helper T cells (THH) )

Specific DefensesSpecific DefensesHelper T Cells Helper T Cells continuedcontinued

Activated helper T cells (TActivated helper T cells (THH) release proteins ) release proteins called cytokines which activate cytotoxic T cells called cytokines which activate cytotoxic T cells (T(TCC) and B cells) and B cells

The activated (TThe activated (TCC) and B cells begin to divide) and B cells begin to divide

Specific Defenses Specific Defenses Cell Mediated ResponseCell Mediated Response

Receptor proteins on theReceptor proteins on the

cytotoxic T cells (Tcytotoxic T cells (TCC) bind to ) bind to

viral antigens displayed by viral antigens displayed by

infected cellsinfected cells Cytotoxic T cells (TCytotoxic T cells (TCC) punch a ) punch a

hole in the cell’s membranehole in the cell’s membrane Your body produces many Your body produces many

cytotoxic T cells (Tcytotoxic T cells (TCC) )

- each specific to a particular antigen- each specific to a particular antigen

Specific DefensesSpecific DefensesAntibody Mediated ResponseAntibody Mediated Response

B cells divide and develop into B cells divide and develop into

plasma cellsplasma cells Plasma cells release large numbersPlasma cells release large numbers

of antibodies of antibodies AntibodiesAntibodies bind to antigens on bind to antigens on

pathogenspathogens Antibodies cause pathogens to clumpAntibodies cause pathogens to clump

holding them until macrophages holding them until macrophages

can engulf themcan engulf them Antibodies are specific to a particular pathogen-your body Antibodies are specific to a particular pathogen-your body

produces the antibodies in response to infectionproduces the antibodies in response to infection

The Specific Defense has The Specific Defense has two phasestwo phases

Primary Immune Primary Immune Response:Response:

--Occurs when the body Occurs when the body has never has never encountered a encountered a pathogen /antigen pathogen /antigen before. before. -Immune system goes -Immune system goes through all of the stepsthrough all of the steps

-After the threat has -After the threat has passed, passed, MEMORY Cells MEMORY Cells are made.are made.

Secondary Secondary Immune Immune Response:Response:The next time the The next time the pathogeninvades pathogeninvades MEMORY Cells MEMORY Cells identify identify the invader and a the invader and a massive volume of massive volume of antibodies are released, antibodies are released, destroying the invader destroying the invader before you feel ill. before you feel ill.

You are immune!You are immune!

VaccinesVaccines

Polio 1952 60,000 cases in the US 3000 fatalities1955 Salk vaccine1979 eliminated in US

How do vaccines work?How do vaccines work? VaccinesVaccines are made up of weakened are made up of weakened

viral particles.viral particles. The weakened particles stimulate a The weakened particles stimulate a

small number of antibodies and small number of antibodies and memory cells to be produced. memory cells to be produced. Primary Immune ResponsePrimary Immune Response

When a the pathogen attacks, the When a the pathogen attacks, the antibody production is larger. antibody production is larger.

Secondary Immune ResponseSecondary Immune Response

Immune ResponseImmune Response

VocabularyVocabulary Pathogen B cells T cellsPathogen B cells T cells MacrophagesMacrophages Nonspecific DefenseNonspecific Defense VaccinesVaccines Primary Immune ResponsePrimary Immune Response Secondary Immune ResponseSecondary Immune Response