i mmune s ystem b asics. h ow a v irus attacks the body. http :// www. youtube. com / watch ? v =r...
TRANSCRIPT
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IMMUNE SYSTEM BASICS
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HOW A VIRUS ATTACKS THE BODY.HTTP://WWW.YOUTUBE.COM/WATCH?V=RPJ0EMEGSHQ&FEATURE=RELATED
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PATHOGENS Any biological agent that causes illness
and/or disease to its host. Also known as a germs, simple as that!
Different types of pathogens include the following:
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HTTP://WWW.YOUTUBE.COM/WATCH?V=NON4MKYQPYA&LIST=PL713E26869E18998B&INDEX=3
Pathogens will trigger the immune system to respond.
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3 MAIN DEFENSES
External Barriers
Non-specific Internal (aka INNATE)
Fever & Inflammatory response
Immune Response
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EXTERNAL DEFENSE
Skin produces Sweat which contains
lysozymes Oil – traps bacteria / fungi
Mucus membranes of digestive and respiratory tract produceMucus to trap foreign particlesCilia sweep the mucus to be
cleared from body
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NON-SPECIFIC INTERNAL DEFENSE
WHITE blood cellsMonocytes and Neutrophils
are able to cross capillary walls
use PHAGOCYTOSIS to engulf foreign invaders
Natural Killer cellsRespond to chemical message from Neutrophils; sensing molecular changes in cells causes the release of cytotoxic proteins into “foreign cell”.
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NON-SPECIFIC INTERNAL DEFENSE
Inflammatory ResponseHistamines make capillary walls
“leaky”RBC, WBC, platelets and fluid cross
capillary walls swelling, redness and warmth in
the injured area PUS formation – tissue debris,
microbes and WBC (dead and alive)
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NON-SPECIFIC INTERNAL DEFENSE
FEVER – triggered if pathogen is in bloodstream or infection is now systemic rather than localized.
102 – 1030 F is beneficial high temp in fighting viral infections and triggers release of interferon.
Interferon literally interferes with viral replication.
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SPECIFIC INTERNAL RESPONSE
aka IMMUNE RESPONSE Use Lymphocytes
B-Cells = humoral T-Cells = cell mediated
Thymus, lymph nodes and spleen house these cells until called into action by interleukins and cytokines.
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Leukocytes (White Blood Cells)
lymphocytes
T cells B CellsNK
Cells
WHITE BLOOD CELLS
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B CELLS B Plasma Cells- when the B
cell produces the antibody for a specific antigen, it begins to clone itself into B plasma cells, that produce more of that particular binding antibody.
These cells release immunoglobulin, or antibodies.
B plasma cells have a 5 to 7 day life-span; all its protein synthesis energy is going into the production of Antibodies, not self preservation.
B Memory Cells- These are the same as B plasma cells, except they remain inactive until the secondary immune response
Secondary immune response is considered anytime the body encounters a pathogen after the first time. Quicker response time.
Primary response is the first time the body encounters a specific pathogen, Lag period before B cells respond.
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T CELLS
T cells
Helper T cell (Th)
Memory T cell
Helper T cell
Killer T cell
Suppressor T cell
Killer T cell (Tk)
Suppressor T cells - in charge of slowing and stopping the immune response after the foreign substance is destroyed.
Helper T cells - secrete lymphokines that direct B cells into producing antibodies and also direct the Killer T cells as to which cell they get to eliminate.
Killer T cells - They find specifically coded infected cells, and then destroy them with cytotoxins. They may be directed by Helper T cells
Memory T cells - derived from Helper T cells, have the same properties as their parent cell, and circulates until the body encounters the pathogen its parent cells were designer for.
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ANTIBODIES & ANTIGENS
Antigens= a fragment of a protein or peptide from the pathogen, taken to the surface of the infected cell and bound in an MHC (major histocompatibility complex) molecule.
The class 1 MHC complex molecule and the foreign peptide form the antigen, which can be read by the receptors on Killer T cells.
CellClass 1 MHC molecule
Antigen
Pathogen
Antibodies are produced by B cells, when stimulated by lymphokines from helper T cells. The antibody attaches to the antigen, completing the signal, coding the infected cells for destruction.
Antibodies are constructed of DNA fragments, making them so unique and almost innumerable.
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ANTIBODIES – PROTEINS CREATED BY B-CELLS THAT “LOCK” DOWN FOREIGN ANTIGENS
Antibodies are shaped to match antigen binding sites called epitopes.
Epitopes are the accessible portion of the antigen – a single bacterial surface protein can have several different epitopes.
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B-CELL RECEPTORS
“Y” shaped proteins extend from cell membrane.
2 heavy chains 2 light chains that
can be rearranged to match antigen.
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T-CELL RECEPTORS
2 parallel protein chains a - chainb – chainThese chains form the recognition site for each different antigen.
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HOW ANTIGEN RECOGNITION BY LYMPHOCYTES WORKS
MHC – major histocompatibility complex Chemical signaling proteins
Class I MHC – found on ALL cells to tell self from non-self
Class II MHC – found on macrophages & B-cells display antigens to Helper T-cells
APC – antigen presenting complex Chemical signaling displays antigen
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CELL MEDIATED IMMUNITY
Helper T-Cells respond to chemical signals presented by macrophage.
Helper T-Cells stimulate cytokines and interleukin which triggers production of B-cells and cytotoxic T-cells.
Helper T cells function in both Humoral & Cell Mediated immunity.
Cell mediated =T-Cell
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CELL MEDIATED IMMUNITY
T-cells attack invaders directlyPerforins released by cytoxic T-Cells
create pores in infected cell resulting in ion/water inflow cell lysis
Effective against intracellular parasites
Infected cell
PerforinsT-Cell
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T-CELLS INTERACTION WITH ANTIGEN PRESENTING CELLS
In both interactions the MHC receptor allows a T-cell to bind which starts defense response.
In (a) an infected body cell alerts cytotoxic cells to destroy infected cell (short term).
In (b) a macrophage displays antigen which triggers immune response (long term).
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The ability to resist a pathogen Two forms of immunity;
◦ ACTIVE – direct exposure that creates immune response.
◦ PASSIVE – induced exposure through vaccination.
WHAT IS IMMUNITY?
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IMMUNITY INVOLVES PRODUCING A PRIMARY IMMUNE RESPONSE Step one – virus or bacteria infects body cell Step two – macrophage recognizes foreign
antigen of pathogen and engulfs it presenting antigen to alert SPECIFIC DEFENSE SYSTEM
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Step three – macrophage activates Helper T-cells Helper T-cells set up the two prong attack of the
immune response
DEVELOPMENT OF PRIMARY IMMUNE RESPONSE - CONTINUED
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Step four –Helper T-cells activate both plasma B-cells and Cytotoxic T-cells
Step five - B-cells form plasma cells which make antibodies to match foreign antigens of pathogen
DEVELOPMENT OF PRIMARY IMMUNE RESPONSE - CONTINUED
antibodies
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Step five part 2- memory B-cells are created to always remember foreign antigen.
Step six – Antibodies made by plasma B-cells
find & attach to pathogens antigens
DEVELOPMENT OF PRIMARY IMMUNE RESPONSE - CONTINUED
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Step seven - Antibodies mark pathogens for destruction.
Step eight - Cytotoxic T-cells locate and destroy infected cell by making a hole in the cell membrane.
DEVELOPMENT OF PRIMARY IMMUNE RESPONSE - CONTINUED
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IMMUNE RESPONSE 2-PRONG ATTACK TRIGGERED WHEN HELPER T-CELLS ARE ALERTED
5b. Creation of Memory B-cell
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IMMUNOLOGICAL MEMORY The reason why vaccines make sense, and we
eventually build a tolerance to certain diseases…
It’s because after every encounter with a pathogen, both the T cells and the B cells differentiate into an inactive form of their parent cell. They remain inactive until the second immune response for that specific pathogen.
Vaccination is an introduction of a dormant or dead pathogen, which allows our body to do its primary immune response without the risk of actual sickness.
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HOW DO VACCINES WORK?
Vaccine contains a dead or weakened pathogen or protein from pathogen.
Most vaccines are only effective against infections before you get them.
Vaccines can wear off overtime booster shots revive immunity.
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IMMUNOLOGICAL MEMORY
Heightened secondary response is due to long lived memory cells as a result of first exposure to antigen A.
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IMMUNE RESPONSE 2-PRONG ATTACK TRIGGERED WHEN HELPER T-CELLS ARE ALERTED