Chapter 5 - Immunity Flashcards
Where are t lymphocytes found
- in the bone marrow
- and migrate to thymus gland where they mature before being released into blood stream
T lymphocytes function
- they can only recognise antigens on the surface of other cells (antigen presenting cells)
- they contain t receptors which attaches to the antigens
4 situations where cells act as antigen presenting cells
1) when a cell is infected with a virus
Antigens from the virus attach to MHC molecules and are presented in the surface of the infected cell
2) when a mutation occurs in a normal body cell forming a cancer cell
Cancer cells produce proteins, that normal healthy cells don’t, which attaches to MHC and present on the cell surface
3) when cells or tissues are transplanted from one indv to another
The antigens in the transplanted cell are not identical to the antigens on the host cell, these antigens will attach to MHC and be presented on the cell surface causing the immune system to identify these antigens as foreign
4) when a phagocyte engulfs a pathogen
The pathogen antigens are displayed on the phagocytes surface
Types of t lymphocytes
1) T helper cells
2) Cytotoxic T cells
3) T regulator cells
4) T memory cells
Function T helper cells
1) they attach to the surface antigens by their T cell receptors causing the T helper cells to be activated
2) once activated the T helper cells:
- undergo mitosis to produce identical clones
- produce interleukins which trigger phagocytes to increase their rate of phagocytosis and stimulate B lymphocytes to divide by mitosis
3) They activate Cytotoxic T cells
Function of cytotoxic T cells
1) cytotoxic T cells identify abnormal or virally infected cells
2) they attach to the cell and release a protein called perforin
3) perforin forms holes in the cell membrane destroying the cell
Function of t memory cells
- they live long
- they rapidly differentiate into cytotoxic T cells if the body is exposed to the same pathogen
Function of t regulator cells
1) down regulates the immune system once the pathogen has been destroyed
2) to ensures that body does not attack self antigens
3) so reduces chance of autoimmune disorders
Role of antigen presenting cells
They present antigens to T helper cells, so they can bind to them, causing the them to be activated
What does the specific immune system do
Recognises indv pathogens and produces a more effective response if it is exposed to the same pathogen
Structure of antibody
They Contain:
1) hinge region - which is flexible and allows the distance between antigen binding site to vary
2) a heavy chain and a light chain
3) disulphide bridges which hold together the chains
4) 2 antigen binding sites, the tertiary structure of the binding site is complementary to the structure of the antigen
5) constant region which has the same structure for all antibodies
6) variable region This is different for each antibody as its shape is complementary to a specific antigen
Function of antibodies
1) they tag foreign bodies so phagocytosis can occur
2) undergo agglutination by sticking pathogens together preventing them from spreading around the body, this helps prevents viral pathogens to invade host cells
3) antitoxins (a type of antibody) stick to bacterial toxins preventing them from harming body cells
Process of cell mediated immunity
1) once the pathogen is engulfed and digested by a phagocyte during phagocytosis the phagocyte acts as a antigen presenting cell as it processes the antigen and attaches it on the MHC molecule displaying the antigen in its surface
2) A T helper cell binds to its complementary receptor to the antigen and contains a surface molecule called CD4 which binds to MHC molecules
3) once the T helper cell is bound to the antigen the T helper cell is activated causing it to produce interleukins which trigger the activated T helper cells to undergo mitosis forming identical clones of the activated T helper cells
Process of humoural immunity (APC = antigen presenting cell)
1) antigens in the blood will bind with their complementary antibody on a B cell. The B cell takes in the antigen by endocytosis then presents it in the cell surface membrane and becomes an APC
2) Through clonal selection the activated T helper cell binds it T cell receptors with the antigens on B lymphocytes surface
3) The T helper cells produce interleukins which activate the B lymphocytes
4) through clonal expansion the activated B lymphocytes undergoes mitosis forming clones of plasma cells and B memory cells
5) the Clones plasma cells undergoes a primary immune response by releasing identical antibodies which binds to the antigens on the pathogen which disables the pathogen , mark it for phagocytosis or triggers agglutination
6) the B memory cells stay in the blood stream until it is exposed to the same pathogen which then it undergoes a secondary immune response where they rapidly turn into plasma cells and release identical antibodies FASTER AND AT A HIGHER CONCENTRATION
Where are b lymphocytes found
In the bone marrow where they mature before being released into the blood
Differences between t lymphocytes and b lymphocytes
T cells
- responsible for cell mediated immunity
- mature in the thymus gland
- secretes interleukins
- have two types of active cells
B cells
- responsible for humoural immunity
- matures in bone marrow
- secretes antibodies
- have only one type of active cell
When a pathogen causes an infection, plasma cells secrete antibodies which destroy this pathogen.
Explain why these antibodies are only effective against a specific pathogen
- Antibodies have a specific tertiary structure
- Antibody is complementary to the antigen
What is active immunity
The stimulation of the production of antibodies by an indv own immune system
What is natural active immunity
When an individual becomes infected with a disease under normal circumstances causing the immune system to be activated
Examples of natural active immunity
- infections - as it’s a naturally occurring process as the pathogen is exposed to an indv causing they’re immune system to be activated resulting in the production of antibodies and memory cells
What is artificial active immunity
When an immune response is stimulated without an indv suffering from any symptoms of a disease
Examples of artificial active immunity
- vaccinations - as it stimulates the activation of B and T lymphocytes triggering the production of antibodies and the function of memory cells
What is Passive immunity
The introduction of antibodies to the body without the immune system being activated
Examples of passive natural immunity
- babies
New babies cannot make antibodies as their immune system is not fully developed,
Developing foetus received antibodies through the mothers placenta
A few days after the baby is born the mothers breast milk is rich in antibodies and at this stage the milk is called colostrum, the antibodies in the milk pass from the baby’s dirge stem system into the blood stream
Example of Artificial passive immunity
- Tetunus
Caused by a bacterial infection which produces toxins once in the body resulting in muscle spasms which can prevent the patient from breathing
It can lead to death before your immune system can respond so patients are injected with antibodies against Tetunus toxins made from a horse
What is a pathogen
A microorganisms that cause a disease
What is an antigen
A glycoprotein that stimulates an immune response
Why are glycoproteins most likely to act as antigens/antibodies
As they have a different shape than the body proteins
4 types of pathogens
Fungi
Protista
Bacteria
Virus
How do bacteria affect the body
- pathogenic bacteria release toxins leading to the symptoms of the disease
- other bacteria enter host cells and prevent them from functioning properly
Structure of virus
Contain:
- genetic material (DNA or RNA)
- capsid that surrounds genetic material
- attachment proteins which allows virus to attach to host cells
- lipid envelope
How do viruses replicate
1) using their attachment proteins they attach to host cells and pass through the cell membrane
2) it then copies itself using enzymes of the host cell
3) the virus particles leave the cell and go invade new host cells where they continue reproducing
Virus affect on body
- prevent host cells from functioning normally
- can lead to the death of host cells
Structure of fungi
- eukaryotic cells
- unicellular or multicellular
What does fungi do to the body and what’s its affect
1) release enzymes to digest the material around them
2) products of digestion are absorbed back into fungal cells
3) this process of digestion can damage the host cells and tissue
4) when they reproduce the fungi releases a large number of spores which causes fungal disease to spread widely
What is the specific defence system against pathogens
the immune system
- the response of the immune system is specific to each type of pathogen
- when the immune system fights off a pathogen it becomes more effective at fighting off a second infection by the same pathogen
What are the Non specific defences against pathogens/ your first line of defence
- skin
- stomach
- tears
- trachea
- (expulsion reflexes)
- (blood clotting)
What does the non specific defence system do
Prevents pathogens from gaining access to the body
How does the skin prevent pathogens from entering the body
- provides a protective layer for the body’s surface
- contains a layer of cells which makes it difficult for pathogens to penetrate the body
- surface of skin is covered with oily sebum produced by the sebaceous glands to form a slightly acidic layer which can prevent the growth of harmful bacteria
- covered with harmless microorganisms which reduces the growth of pathogens by competing for resources
How does the trachea prevent pathogens from entering the body
- lined with a mucous membrane which secrete mucus which traps microorganisms which are then destroyed by phagocytes
- mucus contains the enzyme lysozyme which destroys bacteria by digesting the bacterial cell wall
How does tears prevent pathogens from entering the body
Contains lysozymes which prevent pathogens entering via the yen’s
How does the stomach prevent pathogens from entering the body
The mucus on the lining of the stomach contains hydrochloric acid which help to kill any pathogens on food or water
How does expulsive reflexes prevent pathogens from entering the body
It expels any pathogens that are entered through the mouth or nose by sneezing coughing or vomiting
How does blood clotting prevent pathogens from entering the body
When the skin is damaged the body seals the damages area through blood clotting to prevent any pathogens from entering
Process of phagocytosis
1) phagocyte recognises foreign antigens and is attracted to the chemicals released by the pathogens
2) on the surface of the phagocyte there are receptor binding points that attach to the antigens on the pathogen
3) the phagocyte changes shape and engulfs the pathogen and encloses it within a phagosome vesicles
4) a lysosome within the phagocyte will fuse with the phagosome
5) the lysosome contains a lytic enzyme called lysozyme which hydrolyses the pathogen
6) the soluble products are absorbed and used by the phagocyte
Second line of defence
White blood cells
Phagocytes
3rd line of defence
Lymphocytes
Why are phagocytes non specific
As any non self antigen that is detected will trigger the same response to destroy it
How do vaccines work
1) The vaccine, containing attenuated antigens, is injected into the blood.
2) This stimulates the primary immune response to produce antibodies against the pathogen.
3) Memory cells, capable of recognising these antigens, are produced.
4) On second exposure to this pathogen, memory cells rapidly divide into plasma cells.
5) Plasma cells rapidly produce antibodies against the pathogen.
6) The pathogen is destroyed before any symptoms are experienced.
Explain how vaccines provide protections for populations against disease
herd immunity
- if a large portion of the population has been vaccinated it provides protection to the people who have not been vaccinated as they do not become infected since there are fewer infected people to pass pathogen so unvaccinated people are less likely to come in contact with someone with the disease
Why might vaccines not eliminate diseases
1) herd immunity only works if a high percentage of people have been vaccinated, so when there is less people vaccinated herd immunity breaks down causing an epidemic of an infectious disease
2) Pathogen mutation and antigenic variability - Rapid antigenic changes due to frequent mutations can make vaccines ineffective, as the immune system can no longer recognise the pathogen’s new antigens
3) Pathogen hiding - Certain pathogens can evade the immune system by ‘hiding’ inside cells or inhabiting hard-to-reach body regions like the intestines
4) Vaccine objections - Personal, religious, ethical, or medical objections to vaccination can hinder disease eradication. Misinformation can lead to reduced vaccination rates
Why do people need to be revaccinated every year
- due to antigenic variability which causes a pathogen to change its surface antigens
this makes it difficult to develop vaccines against some pathogens because if the antigens change enough they will no longer be recognised by the immune system. This means that memory cells produced from vaccination against one strain will not recognise the antigens from another strain.
As a result, vaccines need to be changed frequently to provide protection against the most recent pathogenic strains
What are monoclonal antibodies
A single type of antibody that can be isolated and cloned
What are antibodies
Proteins which have binding sites complementary in shape with certain antigens
Uses of monoclonal antibodies
- medical treatment
- medical diagnosis
- pregnancy tests
- ELISA test
Types of medical treatment using monoclonal antibodies
- Direct monoclonal antibody therapy
- indirect monoclonal antibody therapy
What happens in direct monoclonal antibody therapy
- monoclonal antibodies with a complementary shape to the antigens on cancer cells are given to cancer participants
- the antibodies attach to the cancer cells preventing chemicals that enable uncontrolled cell division binding to the cancer cells
- therefore this prevents cancer cells growing without harming normal cells
What happens in indirect monoclonal antibody therapy
- monoclonal antibodies with a complementary shape to the antigens on cancer cells have drugs attached to them
- once the antibody binds to the antigen the drugs are delivered directly to the cancer cells and kills them
- this reduces the harmful side effects that chemotherapy and radiotherapy can produce
types of antibodies used for pregnancy tests
1) mobile antibodies that are complementary to the antigen being tested for and had a coloured due attached to it
2) immobilised antibodies that are complementary to the antigen
3) immobilised antibodies that is complementary to the shape of the first antibody
Process of ELISA test
1) add the test sample from a patient to the base of a beaker where the antigens stick
2) wash to remove any unbound antigens to the base of the beaker
3) add an antibody that is complementary in shape to the antigen you are testing the presence of
4) wash to remove any excess antibody molecules
5) add a second antibody which is complementary in shape to the first, that has an enzyme attached to it and binds to the first antibody and then wash again to remove any unbound second antibodies
6) the substrate for the enzyme is added, which is colourless, produces coloured products in the presence of an enzyme
7j) the presence of the colour indicates the presence of the antigen in the test sample and the intensity indicates the quantity present
Ethical issues of monoclonal antibodies
- creating mono antibodies uses mice to produce the antibodies and tumour cells and can result in the death of mice
How do pregnancy tests work
1) urinate in the absorption tip of the preg test
2) the test contains mobile monoclonal antibodies with small coloured beads attached to them
3) the mobile monoclonal antibodies will bind to the HCG hormone which is only found in pregnant women’s urine, forming a HCG/antibody complex in the reaction zone
4) the urine will move up the test strip to the result window where immobilised antibodies will bind to the HCG complex, causing a line to appear in the window, indicating a positive result
5) the Irvine continues to move up to the control where a line of immobilised antibodies will bind to the mobile monoclonal antibodies, indicating that the test is working
What is HIV
A virus that cause the disease acquired immunodeficiency syndrome, AIDS
What does HIV stand for
Human immunodeficiency viruses
Structure of HIV
Contains:
- reverse transcriptase
- two RNA strands
- capsid - which contains the RNA strands
- matrix proteins - which help maintain the structure of the virus
- lipid envelope
- attachment proteins - allows HIV to attach to host cells
How does HIV replicate
1) attachment proteins attach to receptor on helper T cells (called CD4)
2) fuses with the membrane and the RNA enters the cell
3) Reverse transcriptase converts RNA to DNA
4) DNA is inserted into host DNA
5) DNA is transcribe into HIV mRNA
6) HIV mRNA is translated into viral proteins
7) Viral particles are assembeled and released from the cell through exocytosis
How does HIV lead to AIDS
- HIV causes the death of T helper cells and as the number of T helper cells decrease the patients immune system can no longer function effectively
- as without enough T helper cells, the antibody products by B lymphocytes and the cell mediated immune response will become less effective causing the patient to develop AIDS
Why can’t antibiotics be used in viruses
Viruses don’t have a cell wall
Don’t have metabolism processes
Don’t have bacterial structures
What does the elisa test stand for
Enzyme linked immunosorbent assay
What is the role of disulphide bridges in forming the quaternary shape of the antibody
Joins two polypeptides
differences between active and passive immunity
active
- initial exposure to antigen
- memory cells involved
- antibodies produced and secreted by b plasma cells
- slow as it takes long to develop
- long term immunity as can be produced in response to a specific antigen again
passive immunity
- no exposure to antigen
- no memory cells
- antibodies produced by another organism
- faster acting
- short term immunity as antibody is hydrolysed
explain the effect of antigen variability on disease and disease infection
- antigens on pathogen changes shape due to gene mutations
- so no longer immune as B memory cell receptors can not bind to antigen and antibodies are not complementary to antigen
Types of immunity
Passive
Active
Criteria of successful vaccination programme
- Availability - Suitable vaccines must be affordable and available in large amounts for mass immunisation.
- Minimal side effects - The fewer the side effects from the vaccine, the better the public acceptance.
- Herd immunity - The goal is to vaccinate the majority of the population to achieve herd immunity.
Collagen is a protein produced by cells in joints, such as the knee.
Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease,
a person’s immune system attacks their own cells. RA causes pain, swelling and
stiffness in the joints.
Scientists have found a virus that produces a protein very similar to human
collagen.
Suggest how the immune response to this viral protein can result in the
development of RA.
The antibody against virus (antigen) will bind
to collagen;
2. This results in the destruction of the (human)
cells/collagen;
