Immunity Flashcards
What is a pathogen?
A disease causing microrganism
What does a cell-mediated response involve?
T lymphocytes
What does a humoral repsonse involve?
B lymphocytes
What is an innate response?
First line of defense, attacks generic classes of pathogens
What is an adaptive immune response?
A specific defence system that eliminates almost any pathogen or abnormal cell in the body through immonulogical memory
What is an infection?
Interaction between the pathogen and the bodys various defence mechanisms
What is immunity?
The ability to ward off disease
What do all immune cells come from?
Hematopoietic stem cells
What do hematopoietic stem cells differentiate into?
Lyphoid progenitor or myeloid progenitor
What is the lymphoid lineage?
Lymphocytes
—>T-cells, B-cells and natural killer cells
What is the myeloid lineage?
Ganulocytes,monocytes
—>macrophages and neutrophils
What does the 1st line of defence include/do?
Physical and chemical barriers
What does the 2nd line of defence do/include?
Non-specific inflammatory response & phagocytosis
What is the 1st immune response?
B+T cells
What is the 2nd immune response?
Memory cells
Where are all immune cells derived from?
Bone marrow
What is the specific immune response?
Defense response against a specific foreign or abnormal cell
What is a non-specific immune response?
Initital, immidiate immune reponse against forein antigens vis non-specific antibodies and immune cells
Ie physical barriers and phagocytosis
What are some examples of physical barriers?
- skin
- mucous membranes
- sebaceous + sweat glands
- tears, saliva + secretions
How does the skin act as a barrier?
It contains keratinocytes that act as an impentrable barrier
What do mucous membranes do?
It lines body cavities like the digestive, respiratory and genitourinary tracts.
The epithilial layer has goblet cells which secrete mucous and ciliated cells.
The cilia waft the mucous along sweeping any microorganisms into the stomach where the acid denatures any enzymes that the pathogen may have
What does the sebaceous gland do?
It gives the skin an acidic pH (3-5) which prevents most pathogens from reproducing
What does the stomach acid do?
It has a highly acidic enviroment which breaks down any microbes found in food or drinks
What do tears, saliva and mucous do?
They continually wash away microbes from the surface.
Lysozyme is found in tears which is an antimicrobial and will break down bacteria cell walls
What is the most abundant type of immune cell?
Neutrophil
What is the function of neutrophils?
Phagocytise bacteria
Give pus a white colour
What do dendritic cells do?
They capture antigens and deliver them to the lymph nodes where they are presented to T-cells which mulitply and attack the pathogen
What helps the body to identify self and non-self cells?
Antigens
What are the two types of WBC?
Phagocytes and lymphocytes
Where do B-cells mature?
Bone marrow
Where do T-cells mature?
Thymus gland
What are antigens?
Proteins(glycoproteins or glycolipid) that are on the cell surface of pathogens that stimulate an immune repsonse
What are examples of non-specific immune repsonses?
- inflammation
- lysozyme action
- interferon
- phagocytosis
What happens if an antigen on a pathogen changes?
Lymphocytes and memory cells can’t bind so the host cell becomes infected
What do macrophages develop to become?
Antigen presenting cells
What causes inflammation to occur?
Histamine and other chemicals released by damaged tissues
What does inflammation cause?
Vasodilation of blood vessels
Leaky blood vessels
Increases blood flow to the infected site
More phagocytes are delivered
What does interferon do?
Stops viruses spreading to uninfected cells by preventing protein synthesis in viruses
What do phagocytes do?
Ingest and destroy pathogens
What are the types of phagocytic cells?
Macrophages and neutrophils
What are neutrophils?
- Made in the bone marrow with a lobed nucleus
- Travel in the blood + tissues
- Patrol the body tissues
- Released in large numbers but are short lived
- Engulf and digest pathogens into the phagocytic vacuole
What are macrophages?
-Large long lived WBCs which move into organs and travel in the blood as monocytes
-Don’t destroy the pathogen completely by display it on the surface
(APC)
What is endocytosis?
The process by which cells take in substances from outside of the cell by engulfing them in a vesicle.
What are the stages of phagocytosis?
- The phagocyte is attracted to the pathogen by chemical products on the pathogen. It then moves along the conc. gradient via chemotaxis
- The chemical recptors on the surface of the phagocyte attach to the pathogen
- The phagocyte engulfs the pathogen and encloses it into a phagosome vesicle
- Lysosomes within the phagocyte migroate towards the phagosome and fuse to form a phagolysosome
- The lysosomes release lysozyme which release lytic enzymes into the phagosome to hydolyse the pathogen
- The pathogen is digested and the products are absorbed by the phogocyte into the cytoplasm
What is chemotaxis?
The movement of an organism in reponse to a chemical stimulus
What is the role of antigen presenting cells?
To stimulate other cells involved in the specific immune response system
How is the specific immune response activated?
- Antigen presenting cells interact with T-helper cells that have a complementary receptor
- Macrophages release interlukin 1 which stimulates T-helper cells to release interlukin 2
- Interlukin 2 causes the bone marrow to release wither T or B cells
- If T cells are released it will need the exact receptor
If B cells are released it will need the exact plasma for antibodies - Increased number of cells needed
What is interlukin 1&2?
Cytokines that act as a chemical messenger
Why are B memory cells better than T memory cells?
The antibodies dont destroy pur cell whereas killer T cells attack our cells and immune system
What do cytokines stimulate?
- B cells maturing into plasma cells that secrete antibodies
- Formation of B memory cells
- Activation of cytotoxic T cells which destroy tumour cells and virus infected cells
- Actibation of phagocytes
What do B cells do?
Differentiate into plasma cells that secrete antibodies
What do T cells do?
Cell-mediated immune response
What can T cells differentiate into?
T-helper cells
Killer T cells
T memory cells
What do B cells differentiate into?
Plasma cells
B memory cells
Why is it called the humeral response?
As it involves antibodues which are soluble in blood and tissue
What is clonal selection?
The process through which immature B & T cells go though sp that only certain types are permitted to mature
What is clonal expansion?
An increase in the number of the exact lymphocyte needed by mitotic cell division
What do plasma cells do?
- Secrete antibodies imto blood plasma
- Short lived
- Antibodies destroy enzyme
- Known as primary immune response
What do memory B cells do?
They are part of the seconary immune response. They dont produce antibodies directlybut circulate in the blood and tissue, whenthey encounter a previous antigen, they divide rapidly into the correct plasma cells
What organelles would there be a high quantity of in plasma cells?
rER
Golgi apparatus
Ribosomes
What makes blood cells leaky and causes them to dilate?
Histamines
What indicates that your cells are self?
MHC proteins
What does MHC stand for?
Major Histocompatibility Complex proteins
What do cytotoxic T cells do?
Kill infected cells by producing perforin proteim that makes holes in the cell surface membrane causing the cell to die
What do T helper cells do?
Release substances to activate B lymphocytes and T killer cells
What are antibodies?
Immunoglobulin proteins that have a quaternary structure synthosised by B cells and bind to antigens
What is the structure of antibodies?
Quaternary structure with two heavy and two light polypeptide chains bonded by disulphide bonds
Each chain has a constant and variable region
What is the constant region on an antibody?
Its the same in all antibodies and allows antibody binding
What is the variable region of an antibody?
Antigen binding site which is different on every antibody
What is the variable region made up of?
Sequence of amino acids forming 3D structures
What do antibodies form?
Antigen-antibody complexes
What is the hinge region of sn antibody?
Allows flexibility when the antibody binds to the antigen allowing more than one antigen to bind
What does the antigen binding cause?
It immobilises the antigen
How do antibodies inactivate antigens?
- Neutralisation
- Agglutination
- Precipiation of soluble antigens
- Actibation of complement
- Attach to the flagella immobilising the bacteria
- Opsonisation
What is neutralisation?
The pathogen may use the antigen to bind to a host cell. If an antibody binds to the antigen it prevents it happening
What is agglutination?
Some antibodies have several variable regions allowing it to bind to multiple antigens. This sticks pathogens together preventing them from entering the host cell.
What is precipitation of soluble antigens?
Soluble antigens stuck together to form precipitate to be engulfed
What is activation of complement?
Tag foregin cells for destruction by phagocytes.
Produce complement protein which ruptures the cell walls of the pathogen which causes water to enter and the cell to burst
What is opsonisation?
The process by which a pathogen is marked for ingestion and destruction by a phagocyte
What is active immunity?
When the body is exposed to a pathogen and produces its own antibodies
What is passive immunity?
Short term immunity using antibodies produced from outside the body from another human or animal ie vaccination
What do hybridoma cells do?
Divide endlessly to produce a clone of one specific type of hybridoma cell
What is the role of an activated B cell?
To multipy to form clones of plasma B cells
How does HIV affect the immune system adversely?
Progressive reduction in number of active lymphocytes which causes a reduction in antibody productin
What 2 cells fuse together during monoclonal antibody production?
Plasma and tunmour cells
What is an example of active immunity?
Antibodies being produced after defence mechanisms have been stimulated by antigens
What do RNA molecules in a virus do?
Carry genetic instructions and information to make DNA/new viral proteins
How are new viruses produced after HIV has infected the T cell?
- DNA copy made up of viral RNA through reverse transcriptase reversing RNA INTO DNA
- DNA moves into the nucleus and uses viral DNA to make viral proteins and mRNA
- mRNA provides instructions to make new viral proteins which pass out of the nucleus and use the cells protein synthesis to make new HIV viruses which bud off
How does antihen variation affect the use of vaccines?
-Memory B/T cells cannot recognise the antigen so the previous antibodies arent effective as they dont have a complementary shape
What is an autoimmune disease?
A disease in which the body’s immune system attacks healthy cells
What are some examples of autoimmune diseases?
Lupus, rheumatoid arthritis
What is natural active immunity?
The productionof ones own antibodies or T cells as a result of infection or natural exposue to antigen
What is artificial active immunity?
Acquiring ones own immunity against an attenuated pathogen
Example of natural passive immunity?
Breastfeeding
Example of natural active immunity
Infection
Example of artificial passive immunity
Injection of antibodies or antitoxins
Example of artificial active immunity
Vaccination
What are the different types of vaccine?
Inactivated
Attenuated
Preparation made from antigens only
What is an attenuated vaccine?
Alteration of the virus to make it less harmful
How do vaccines work?
Once the vaccine is injected, an immune response is triggered
Memory cells produced remain in the blood
Secondary response allows for rapid production of antibodies
The pathogen is destroyed before causing symptoms
What does the success of a vaccination programme depend on?
- Economically avaliable quantities
- Few less severe side effects
- Ease in transport, storage, production and administation
- Number needed for herd immunity
- Cost
What are the ethical issues around the use of vaccines?
- Production may involve animals
- Long term side effects
- Clinical tests may be fatal
- Should they be compulsory
- Expensive
What does HIV stand for?
Human Immunodeficiency Virus
What type of virus is HIV?
Retrovirus
Catalyse DNA from RNA to replicate
How is HIV transmitted?
Blood, semen, vaginal secretions, breast milk, sharing needles
What does HIV do?
Destroys the immune system and causes AIDS
What does AIDS stand for?
Aquired Immune Deficiency Syndrome
What is the structure of HIV?
Two single strands of RNA Attachement proteins Lipid envelope Protein capsid Reverse transcriptase
How does HIV replicate?
HIV binds to CD4 receptor on t helper cell -capsid fuses w/ cell surface membrane -RNA + enzymes enter t cell -reverse transcriptase reverses RNA into HIV DNA -DNA moves into T cell nucleus creating mRNA -mRNA has instructions making viral proteins -viral particles assembled + break away from T cell w/ piece of membrane to make lipid envelope
What is the course of the HIV infection?
Acute HIV syndrome
Chronic phase
Disease stage
Advancd AIDS
How does HIV cause the symptoms of AIDS?
It reduces the number of T-helper cells so very few B cells are activated which means the body cannot fight off infections - AIDS
Why are antibiotics ineffective against viruses?
Viruses use host cells to carry out metabolic processes as they lack their own metabolic pathways therefore antibiotics cannot disrupt it.
Viruses have a protein coat not a cell wall.
How are antibiotics effective against bacterial infections?
- Inhibit enzymes needed for synthesis and assemble peptide linkages in bacterial cell walls
- They weaken the cell wall as they cannot withstand the pressure causing water to enter and the bacterium to burst
What are monoclonal antibodies?
Antibodies produced from a single group of genetically identical B-cells
How are monoclonal antibodies produced?
- Mouse is injected with an injection of antigens to stimulate production of antibodies - Plasma cells isolated from spleen - Plasma cells fuse with tumor cells to form a hybridoma through detergent breaking down membranes - Hybridoma divides produces large amounts of identical antibody molecules required
How are monoclonal antibodies used?
Targeting medication to specific cell types
Medical diagnosis
Pregnancy testing
ELISA tests
How are monoclonal antibodies used to target medication?
Antibodies produced are specific to the antigen allowing receptors to attach
These block chemical signals
Eg cancer signals leading to uncontrolled cell growth
How are monoclonal antibodies used in medical diagnosis?
-produce AB specific to antigen + interacts w/ antigen -> wash removing unbound -antibody w/ enzyme attached -> bind to antigen -substrate added -enzyme converts colourless substrate to colored product if present
How are monoclonal antibodies used in pregnancy tests?
-strip coated w/ antibodies specific to hormone, HCG w/ coloured particles -HCG binds to antibodies when dipped in urine + diffuses up strip -immobilised MA bind with HCG giving appearance of fixed blue Line -small window w/ immobilised AB bind with coloured mobile AB
What does ELISA stand for?
Enzymes-linked Immunosorbent Assay
What are the ethical uses of monoclonal antibodies?
Production involves the use of mice
Drug trials against arthritis and leukaemia resulted in multiple organ failure
Some deaths in trials and treament plans
How are monoclonal antibodies used in seperating one type of molecule from a mixture?
MA immobilised on resin beads
Mixture is poured over beads
Target molecules attach to AB
Beads washed with substance releasing molecules
How does the direct sandwich ELISA test work?
Antigens bound to well
Wash to remove the excess and unattched antigens
Add the antibody specific to the antigen
Wash the surface to remove excess AB
Add the entibodies with an enzyme conjugated
Substrate added
Changes colour if present
How does the direct ELISA test work?
Antigen or sample is immobilised directly on the plate
Conjugated antibody binds to the antigen
Substrate added, producing a colour change if the enzyme substrate complex is formed
How does the indirect ELISA test work?
Antibody added to the well The sample is then added, allowing antigen antibody complexes to form Enzymes conjugated AB Added binding Substrate added=colour change
How do anti-viral drugs work?
They block receptors, preventing viruses from binding with healthy cells
This lowers the viral load supressing them form dividimg and infecting
This reduces virus transmission
Inhibits molecular interactions and the functions that viruses need to replicate
