Cell Immunity By The Spec Flashcards
What molecules enable an immune system to identify
Pathogens
Cells from other organisms of the same species
abnormal body cells
toxins.
Antigen definition
The effect of antigen variability on disease and disease prevention.
Phagocytosis definition
The subsequent destruction of ingested pathogens by lysozymes.
What to t-lymphocytes do
produce an immune response when they are exposed to a specific antigen
When do t cells bind to an antigen
if it is present on the surface of an antigen-presenting cell
What is an antigen-presenting cell
An antigen-presenting cell is one of the host’s cells that has been invaded by a pathogen and is displaying the antigen on its cell surface membrane
What do antigen-presenting cells do?
1) Present antigens from toxins, foreign cells and ingested pathogens
2) Help recruit other cells to produce specific immune response
3) Once the surface receptor of T cell binds to complementary antigen on antigen presenting cell becomes sensitised and divides to produce clone cells
Examples of antigen presenting cells
Macrophages and dendritic cells
What do T lymphocytes do
Those with receptors specific to an antigen divide by mitosis to increase in number
What do T lymphocytes differentiate into
Helper T cells
T killer cells
What do helper t cells do
Assist other white blood cells in the immune response
Release cytokines
Increase rate of phagocytosis
What do cytokines stimulate
-Maturation of B lymphocytes into antibody-secreting plasma cells
-memory B cells
-Activation of cytotoxic T cells, that destroy virus infected cells and tumour cells
What do T killer cells do
-Patrol the body looking for antigen-presenting body cells
-Attach to foreign antigens on CSM of infected cells and secrete toxins that kill infected body cells
Example of T killer cells
Perforins
Secreted by T killer cells punch a hole in CSM of infected cells allowing toxins to enter
Summarise T killer and helper cells during an immune response
1) infected body cell with antigens displayed
2) t helper and killer cells bind to complementary antigens on antigen presenting cell
3) Helper t cells = mitosis, secrete cytokines that stimulate B cells that form plasma and memory cells
3) Killer t cells = divide by mitosis, secrete toxins that kill infected body cell
What are lymphocytes and the two types
Type of white blood cell
Smaller than phagocytes with large nucleus
T lymphocytes = t cells
B lymphocytes = b cells
What do immature t lymphocytes do
leave the bone marrow to mature in the thymus
What do mature t lymphocytes do
have specific cell surface receptors called T cell receptors which have a similar structure to antibodies and are each specific to one antigen
What happens when T lymphocytes encounter their specific antigen
Activated when bind to specific antigen presented by our cells
Antigen-presenting cell might have been invaded by a pathogen displaying the antigen on its CSM
The activated T lymphocytes divide by mitosis and undergo helper and cytotoxic t cells roles
What can mature B lymphocytes do
Code for antibodies
(Each lymphocyte can make one type of antibody)
Clonal selection
IF antigen enters B lymphocyte cells with the correct cell surface receptors they will recognise and bind to it (clonal selection)
What can antibodies from b lymphocytes produce
Part of the antibody can form glycoprotein receptors that are specific to a certian type of antigen
What do b lymphocytes turn into when they bind with antigens inside a cell
Differentiate into plasma cells and memory cells through clonal expansion (mitosis)
Describe a primary immune response using B lymphocytes
1) B lymphocyte has an antibody receptor specific to the receptor on the antigen
2) The selected B cell divides by mitosis forming plasma and memory cells
3) Plasma cells secrete antibodies that are specific with the antigen that has entered the body
Uses of monoclonal antibodies
Pregnancy tests, diagnosing HIV, detecting the presence of pathogen, detecting cancer cells
How do you monoclonal antibodies detect wher blood clots are
1) Inject a mouse with human fibrin
2) Activates the plasma cells to produce antibodies against fibrin
3) Cells are collected from the mouse spleen
4) Plasma cells are then fused with tumour cells forming hybridomas that produce antifibrin antibodies
5) A radioactive chemical is attached to the antibodies to detect where antibodies are binding to fibrin
6) Gamma ray camera is used to detect where these antibodies have attached (shows where blood clots can be found)
How do you test for HIV using monoclonal antibodies
1) HIV antigen attached to test plate
2) Blood sample being tested passes on plate and bind to antigen on HIV antibodies, and wash the plate
3) A monoclonal antibody is passed over the plate, antigen of HIV will bind to monoclonal antibody if present
4) A dye is passed over the plate (chromogen) catalysing a colour change to the enzyme so you can see if the HIV is present
Therapeutic uses of monoclonal antibodies
1) Treatment of rabies (inject pure antibodies)
2) Prevent organ rejection from transplants
3) Autoimmune therapies (asthma)
4) Treatment of diseases by binding to cell surface receptors on B cells causing death of cells
5) Prevent blood clots
What are some defence mechanisms our bodies have against pathogens
1) Prevent entry of pathogens (physical and chemical, skin, tears, mucous, saliva)
2) Inflammation (swell region invaded by pathogen)
3) Recognising foreign cells (specific response, targeting pathogens)
What molecules identify foreign cells
Usually proteins
Part of the phospholipid bilayer such as glycoproteins
Where are surface proteins (glycoproteins) found on
Pathogen cells
Abnormal body cells
Toxins
Cells from other individuals from same specie (organ transplants)
What are antigens purpose
Allow cell to cell recognition
Two types of antigens
Self antigens and non self antigens
Self antigens = dont produce immune response
What are phagocytes
White blood cells constantly produced in the bone marrow
What do phagocytes do
Remove dead cells and invasive microorganisms
Carrying out a non-specific immune response
What are the two types of phagocytes
Neutrophils
macrophages
What do neutrophils do - endocytosis
1) Chemotaxis = chemicals released by pathogens attract neutrophils to where they are located
2) Neutrophils move towards pathogens with antibodies on their surface
3) Antibodies stimulate neutrophils to attack the pathogens as neutrophils have specific receptor proteins that recognise anybody molecules and attach to them
4) When attached the CSM of the neutrophil extends around the pathogen engulfing it within the phagocyte vacuole
What are lyososomes
Membrane organelles that contain lysozymes
What do lysozymes do
Digestive enzymes
Digest unwanted material present in cells
What is a phagosome
The phagocytic vacuole formed around a pathogen once its been engulfed by a neutrophil
What does a lysosome do
Fuses with the membrane of the phagosome and releases lysozymes to digest the pathogen
What happens to neutrophils after they kill and digest a pathogen
Die
Pus is a sign of a neutrophils death
Stages of phagocytosis
1) Attraction (chemotaxis)
2) Recognition and attachment
3) Endocytosis
4) Bacteria with a phagocytic vacuole
5) fusion of lysosomes and phagocytic vacuole
6)Killing and digestion
Where are macrophages
Move into organs
WHat are macrophages roles
1) Initiate an immune response
2) Cut pathogens open to display antigens of pathogens on surface
3) Displayed antigens from antigen-presenting cell can be recognised by lymphocytes
What are antibodies
Globular glycoproteins called immunoglobulins
What strucutre to antibodies have
Quaternary structure with two heavy/ long polypeptide chains bonded to disulfide bonds to two light/ short polypeptide chains
Each polypeptide has a constant region and variable region
What does the constant region in an antibody do
Determins the mechanism used to destroy the antigens
What does the variable region do
Antibodies are different for each antibody
Antibody attached to antigen to form an antigen-antibody complex§
What does the end of the variable region site have
Antigen-binding site
THey vary greatly for specificity for binding to antigens
What is an epitope
Part of the antigen which binds to the antibody
What is the hinge region
gives flexibility for antigen binding site to be placed at different angles when binding to antigens
Where are the light and heavy polypeptide chains
Heavy at bottom
Light at top
Y
How do antigen-antibody complexes form
Antibody collides with a foreign cell that possesses a non-self antigen with a complementary shape, they bind to form an antigen antibody complex
What is agglutination and the advantage
Antibodies have two antigen-binding sites (top of Y)
Bind more than one so pathogens can clump together
Phagocytes can often phagocytose many pathogens at the same time when clumped together
What does the binding of antigens to antibodies do
Neutralises the pathogen or acts as a marker to attract phagocytes to engulf and destroy the pathogens
What do B lymphocytes form
Plasma and memory cells
What is the difference between primary and secondary immune responses
Primary = newly encountered antigen
Secondary = previously encountered
Describe what happens in a primary immune response
1) Only one of these B cells has an antibody receptor that is specific to the shape of the antigen that has entered the body
2) The selected B cell divides by Mitosis and turn into plasma or memory cells
3) Plasma cells secrete antibodies that specifically combine with the antigen that has entered the body
SLOW PROCESS
Describe waht happens after the primary immune response -> the secondary immune response
4) The antigen enters the body for some time
5) Memory cells divide to form more plasma cells which secrete antibodies
FAST
WHat happens when a T lymphocyte comes into contact with the right pathogen
T lymphocyte receptor binds to complementary antigen
T lymphocyte is activated
What is attached onto the surphace of a b lyphocyte
Antibody
How are neutrophils adapted for their roles
Multilobed nucleus allows the cell to be flexible
Glycogen granules store glucose which allow the cell to carry out respiration for energy for phagocytosis
Lysosomes contain lysozymes for the cell to digest pathogens
Process of phagocytosis
Neutrophil engulfs pathogen which is then contained within a phaogosome vacuole
The phagosome fuses with a lysosome inside the cell releasing lysozymes
The lysozymes digest the pathogens and digested parts of the pathogen are displayed on the cell surface membrane of the neutrophil
WHy do antigen presentation lead to a specific immune response
1) T cells with complementary receptors bind to antigens and are activated
2) B cells with complementary antibodies bind to antigens and are activated
3) Activated T lymphocytes divide by mitosis/ clonal expanasion so more lymphocytes are produced specific to the antigen
Histamines are chemicals. How do they assist phagocytes
Phagocytes are large cells that are contained within blood vessels
More permeable capillary walls mean that phagocytes can move into tissues directly to the site of cell damage
How are b lymphocytes activated
Chemicals released by T helper cells bind to complementry receptors on the cell surface
Antibodies on the cell surface of the b cell bind to complementary antigens on the surface of pathogens
