Immune SystemImmune System

An open wound allows An open wound allows ‘germs’ to enter the body.‘germs’ to enter the body.

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 response.immune response.

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

Your Body’s Defenses Your Body’s Defenses AgainstAgainstDiseaseDisease

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

Specific DefensesSpecific Defenses: Immune Response : 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

Second Line DefensesSecond Line Defenses

Inflammatory ResponseInflammatory Response Damaged cells release histamines Damaged cells release histamines - histamines cause blood vessels to dilate - histamines cause blood vessels to dilate

(open) bringing blood to the area.(open) bringing blood to the area.

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

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

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

White Blood cells White Blood cells - - Macrophages – “Big Eaters” engulf Macrophages – “Big Eaters” engulf and kill pathogensand kill pathogens - Neutrophils-engulf bacteria and - Neutrophils-engulf bacteria and release chemicals that kill the bacteria release chemicals that kill the bacteria and themselves.and themselves.

- Natural Killer Cells – recognize - Natural Killer Cells – recognize and kill and kill virus infected cells and tumorsvirus infected cells and tumors

Histamines are released Blood vessels dilateHistamines are released Blood vessels dilate

and leak and leak

MacrophageMacrophage

Temperature Response - Temperature Response - Fever – Fever –

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

-pathogenic bacteria don’t grow well at higher -pathogenic bacteria don’t grow well at higher temp, their enzymes denature and they die.temp, their enzymes denature and they die.

ProteinsProteins - - Complement ProteinsComplement Proteins: : kill pathogens by kill pathogens by

punching a hole in the cell membranepunching a hole in the cell membrane

- - InterferonInterferon: : a protein released by cells infected by a protein released by cells infected by viruses -causes nearby cells to release an enzyme viruses -causes nearby cells to release an enzyme preventing the virus from reproducingpreventing the virus from 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 antigen mustmust be known be known

- - the specific immune the specific immune

response is tailored to response is tailored to

the specific pathogen the 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 substance to release substance to

activate Helper T cell.) activate Helper T cell.)

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

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

Cell Mediated ResponseCell Mediated Response

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 - each specific to a particular

antigenantigen

Antibody 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 Antibodies bind to antigens on Antibodies bind to antigens on

pathogenspathogens Antibodies cause pathogens to Antibodies cause pathogens to

clump holding them until macrophages clump holding them until macrophages

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

body produces the antibodies in response to infectionbody produces 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

PolioPolio 1952 60,000 cases1952 60,000 cases in the USin the US 3000 3000 fatalitiesfatalities1955 Salk vaccine1955 Salk vaccine1979 eliminated in 1979 eliminated in USUS

How do vaccines work?How do vaccines work?

VaccinesVaccines are made up of weakened / are made up of weakened / dead viral particles.dead 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

Plant Immune Responses:Plant Immune Responses:

1) When bacteria come into contact with a plant cell, the plant cells detect its presence

due to receptors called PRR.

A signalling pathway is activated. Molecular events occur and the bacterial growth is

stopped.BASAL DEFENCE was activated.

2) Bacteria often have a Type III secretion system which allows them to directly inject

their proteins into the plant cells.

Some of these proteins can stop a plant cell’s Basal Defence. If this happens, then the bacteria continues growing and the plant

develops a disease.

Plant cells have proteins which can recognize these bacterial proteins and neutralize them.

When a recognition occurs, the protein essentially blocks that of the bacteria and

creates a new pathway.

This new pathway allows the plant cell to become resistant to the attacks of the

bacteria.