3.2 Chapter 5- Immunity Flashcards
What are interactions between different types of cell involved in?
Disease, recovery from disease and prevention of symptoms occurring at a later date.
How does immunity prevent symptoms upon reinfection?
If exposed to the same antigen, or antigen-bearing pathogen, this generates a faster immune response.
What happens if a pathogen overwhelms defences?
Death
How does immunity work?
1.Defence mechanisms overwhelm the pathogen leading to recovery.
2. The body is better prepared for the 2nd infection and kills the pathogen before harm occurs.
What is the first defence mechanism?
Primary defence (skin, physical and chemical defence)
What is the second defence mechanism?
Secondary defence (White blood cells)
What do phagocytes respond to, what are the features of this response and how do they work?
General pathogens- non-specific
Immediate response.
Ingest and destroy pathogen.
What do T cells respond to, what are the features of this response and what is that response called?
Respond to specific pathogens
Longer lasting response
Cell mediated Immunity
What is the response of B lymphocytes called?
Humoral response
What are T lymphocytes and B lymphocytes an example of?
Specific defence mechanisms.
What are physical barriers and phagocytes an example of?
Non- specific defence
How many different types of lymphocytes are there and why?
Tens of millions
To recognise different antigens
How do lymphocytes develop in the foetus?
The foetus rarely gets infected as protected by placenta which acts as a barrier to infection.
The mother provides antibodies to the foetus from the placenta.
Foetuses lymphocytes collide almost only with own cells and if they generate an immune response they die or are supressed.
The remaining lymphocytes are for non- self material- respond to foreign antigens.
How are lymphocytes developed in adults?
- Formed in the bone marrow where they only encounter self antigens.
- If shows an immune response to them- undergo programmed cell death before differentiate into mature lymphocytes.
- No clones appear in the blood- only non-self recognising lymphocytes.
When are lymphocytes not formed?
In response to an infection- already exist.
Why does the large number of lymphocytes help the immune response?
10s of millions
So many- when an infection occurs high probability already at least one lymphocyte will have a complementary receptor to the pathogens antigen protein and recognise it.
What does the large number of lymphocytes mean there are?
Few numbers of each type of lymphocytes.
How does the small number of each type of lymphocyte impact the immune response?
Causes clonal selection.
The small numbers of lymphocytes complementary to the pathogen have to come into contact with the pathogen and divide and build up so they can destroy the pathogen.
Causes a time lag.
What is an antigen?
A foriegn (non-self) protien that stimulates an immune responce.
What are antigens often in the form of and what is their role?
Proteins embedded within the membrane that allow recognition of self and foreign cells by the immune systems.
What can also be another form of antigen?
Hint: Begins with T
Toxins produced by bacteria
What is the difference in the response to foreign (non-self) antigens and to self antigens and why?
Foreign antigens trigger an immune response.
Self antigens do not trigger an immune response.
Otherwise white blood cells would attack the organisms own cells
Why are antigens often proteins?
Proteins have a large variety of specific tertiary structures.
What do antigens enable the immune system to identify?
Hint: 5 points
- Pathogens- e.g. bacteria
- Abnormal body cells- cancerous or pathogen infected
- Toxins- poisonous molecules- often released by bacteria
- Cells from other individuals of the same species.
- Cells infected by a virus
Why is the immune system recognising cells from a different organism of the same species problematic?
- Not good for transplants
e.g. organ/ blood transplant
Transplants often destroyed- rejected by immune system. - To minimise rejection- transplants genetically matched as close as possible and immunosuppressant drugs are taken.
What is a phagocyte?
A type of white blood cell that performs phagocytosis. Often either a neutrophil or a macrophage.
What is phagocytosis?
Engulfment of large particles e.g. bacteria in vesicles formed by the cell surface membrane.
Where are phagocytes found?
In blood and tissue fluid. Move from the blood vessels and transported into tissue fluid.
Describe phagocytes role/ response?
Not to do with phagocytosis
Defend against pathogens that enter the body. First cells to respond to the immune system trigger fast. Non- specific response.
Describe the process of phagocytosis
Hint: 7 steps
- Chemical products of non-self cells attract phagocytes.
- The phagocyte recognises the foreign antigen and attaches to it with receptors.
- Engulfs pathogen or non-self material (surrounds by cell membrane) forming a vesicle called a phagosome.
- Lysosomes fuse with vesicle
- Lysozymes- hydrolytic enzymes- hydrolyse/ break down/ digest the pathogen e.g. hydrolysis of the bacterial cell wall.
- Soluble products absorbed into the cytoplasm. Indigestible material removed.
7.The phagocyte presents the antigens on the cell membrane to activate other immune system cells. Becomes an antigen presenting cell i.e a macrophage.
What response do T Lymphocytes produce?
- Cell mediated responce
- Specific- respond to specific antigens
- Slow but long lasting
What type of cells can T lymphocytes be?
- Helper T cells
- Cytotoxic T cells
How are T lymphocytes produced?
- Produced in the bone marrow.
- Mature in the thymus
What do T Cells respond to?
Respond only to antigens on abnormal body cells- cell mediated immunity:
1. Organisms own cells that have been infected by non-self material e.g. Cells invaded by a virus presenting virus antigens.
2. Antigen presenting cells. Often foriegn antigens from phagocytes presenting antigens on the cell surface membrane.
3. Cells of different organisms from the same species.e.g. transplanted cells presenting different antigens on their cell- surface membrane
4. Cancer cells displaying different antigens- tumour markers
What are cells displaying foriegn antigens called and where do they present antigens?
Antigen presenting cells.
Present antigens on cell surface membrane.
What type of response do T lymphocytes create.
Cell mediated immunity/ a cellular response.
How are T lymphocytes activated?
Receptor proteins on surface bind to a specific complementary antigen on antigen presenting cells e.g. phagocytes activating it.
Why are there vast numbers of T cells?
Respond to a single antigen.
Each for a different antigen so many different types.
Describe the helper T cells responce:
Hint: 3 steps.
- Receptors on specific helper T cells bind to antigens on antigen presenting phagocytes.
- This activates the T cell- divides rapidly by mitosis and forms clones
- The cloned T cells can then become:
a. Helper T cells that release chemical signals that stimulate B cells to clone and form plasma cells that secrete antibodies.
b. Develop into memory cells and stimulate a rapid responce to future infections of the same pathogen.
c. Helper T cells that release chemical signals that activate and stimulate phagocytes to perform phagocytosis
d. Helper T cells that activate cytotoxic T cells.
What happens when T cells are activated?
They are cloned by mitosis (clonal selection).
What can T cells become after they are activated?
- Memory cells- activate B cells and create a rapid response to future infection.
- Helper T cells- release chemical signals that activate and stimulate phagocytes to perform phagocytosis or specific B cells to secrete antibodies
- Cytotoxic T cells
What do Cytotoxic T cells do?
Kill abnormal body cells and cells infected by pathogens.
How do cytotoxic T cells perform their role?
- Produce perforin protein
- Makes holes in cell- surface membrane.
- Membrane becomes permeable to all substances, water and ions enter the cell by osmosis/ diffusion and the cell can no longer function and is destroyed. (demostrates membranes importance).
What are Cytotoxic T cells most effective against?
Viruses as they replicate inside cells.
Why are body cells sacrificed by Cytotoxic T cells.
To prevent viral replication.
What type of immunity do B cells produce and why is it called this?
Humoural immunity- antibodies soluable in blood and tissue fluid.
Describe the features of humoural immunity.
- Specific, slow responce
- Long term immunity
How are B cells produced?
By stem cells in the bone barrow. Mature in the bone marrow.
Why are there many different types of B cell?
- Large variety of antigens but only one type of B cell is complementary to each antigen.
- Each B cell has a different antibody complementary to antigens to form antigen- antibody complexes.
- Ensures there is at least one complementary B cell to every type of antigen.
Describe the structure of a B cell:
Covered in antibodies on their membrane- each cell has different specific antibodies.
Describe clonal selection in B cells (the main type):
- The antibody on a B cell binds to the complementary antigen.
- The antigen is processed- enters to B cell and gets presented on the B cells surface.
- T Helper cells bind ot the processed antigens and stimulate B cells to divide by mitosis and clone into identical B cells that may become plasma cells or memory cells. Each produces an antibody specific to the antigen.
How does clonal selection help immunity?
Produces a rapid response and a large number of antibodies in response to infection.
What type of antibodies do B cells produce?
Monoclonal antibodies- a single type of antibody specific to the antigen.
Describe what plasma cells do and the features of what they do (in detail).
Secrete antibodies into blood plasma. Last only a few days but secrete many antibodies complementary to the antigen to form antigen- antibody complexes and prepare the antigen and pathogen for destruction.
Describe the features of memory cells.
- Long living
- Provide long term immunity.
- Circulate in blood and tissue fluid.
Name and describe the response of memory cells:
Hint: 5 steps
The secondary immune responce:
1. Memory cells encounter the same antigen the B cells defeated before.
2. Memory cells divide rapidly and develop into plasma cells and more memory cells.
3. The plasma cells produce antibodies to destroy the pathogen.
4. A higher concentration of antibodies is secreted and faster than the primary responce. This ensures the infection is destroyed before any harm or symptoms occur.
5. The new memory cells circulate ready for future infection.