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.