Cell recognition and the Specific and Non Specific response Flashcards
What is an antigen
- Foreign molecule
- That stimulates an immune response leading to the production of an antibody
They are also soluble and are transported in bodily fluids
How are cells identified by the immune system
- Each type of cell has specfic molecules on its surface that identify it
- Often proteins have a specofic tertotary structure or glycoproteins or glycolipids
What is an example of a specifc and non specific response white blood cells?
Specific: Lymphocytes
Non Specific: Phagocytes
What does it mean by non specific response
Phagocytes will respond exactly the same no matter what the non self cell is being detcted
What types of cells and molecules can the immune system identify (4)
- Pathogens (diesease causing miceoorganisms) e.g. viruses bacteri aand fungi
- Cells from other organisms of the same species e.g. organ transplant
- Abnormal body cells e.g. tumor cells
- Toxins released by some bacteria
Describe phagocytosis of pathogens(5)
- Phagocyte attracted by chemicals/recognises foregin antigens on pathogen
- Phagocyte engulfs pathogen by surrounding it with its cell membrane
- Pathogen contained in vesicle called a phagosome in cytoplasm of Phagocyte
- Lysosome fuses with Phagosome and releases lysozomes
- Lysozomes hydrolyse pathogen
What does it mean by specific immune response
A response to an exact antigen on the surface of cells
Where are lymphocytes, Tcells and B cells made
- Lymphocytes are made in the bone marrow
- B cells are also made in the bone marrow and are matured there
- T cells are made in the thymus
What does the Cell mediated response involve in terms of cells
T cells and Body cells
What are Antigen Presenting Cells (APC) and give 4 examples of them
APCs are cells that present a non self antigen on thier surface
* Infected body cells- They present the viral antigens on thier surface
* Phagocytes- A phagocyte ,that has engulfed and destroyed a pathogen, will present the antigens on thier surface
* Transplanted cells- Have different shaped antigens on their surface compared to your self cells
* Cancer cells- Have abnormal shaped self cells
Why is the term Cell mediated response called the cell mediated response
Because the T cells involved only respond to antigens which are presented on cells and not antigens in fluids such as blood (humoral response)
Describe the response of T lymphocytes to a foreign antigen (Cell mediated response) (6)
- T lymphocytes recognise antigen presenting cells
- Specific helper T cells with complementary receptors (on cell surface) bind to an antigen on antigen presenting cell
- They activate and divide by mitosis to form clones which stimulate:
-Cytotoxic T cells–> destroy infected cells/tumour cells
-Specific B cells(humoral response)
-Phagocytes-Engluf pathogens by pahgocytosis
What do cytotoxic T cells do
- Destroy abnormal/infected cells
- They release a protein called perforin-Embeds in the cell surface membrane and makes a pore so that substances can enter and exit the cell—> leads to cell death
Where are cytotoxic T cells most commonly used in and what do they do to body cells
- Viral infections because viruses infect body cells
- They also sacrifce body cells to prevent viral replication
What type of cells are involved in the humoral response
B cells and Antibodies
How do B cells activate clonal selection
- B cells take in an antigen by endocytosis and then presents it on its cell surface membrane
- When the B cell collides with a helper T cell receptor, this actiavtes the B cell to go through clonal selection
What cells can B cells differentiate into and what do they do?
Plasma cells-Make antibodies
Memory B cell-Can rapidly divide into plasma cells upon secondary exposures to an infection to make large numbers of antibodies rapidly
What is the life span of Memory B cells and Plasma cells
Memory B cells- Can live for decades
Plasma cells- Short lived
How do memory B cells prevent symptoms from occuring when re-infected with a pathogen
- Memory B cells rapidly divide by mitosis forming plasma cells
- Large numbers of antibodies produced rapidly which destroys the pathogen
Describe the response of B lymphocytes to a foreign antigen (the humoral response) (6)
- Clonal selection
-Specific B lymphocyte with complemntary receptor (antobody on cell surface) binds to antigen
-So this is then stimulated by helper T cells (which releases cytokines)
-So divides (rapidly) by mitosis to form clones - Some differentiate into B plasma cells–> Secrete large amounts of (monoclonal) antibody
- Some differnetiate into B memory cells–> Remain in blood for secondary immune response
What are antibodies? (3)
- Quarternary structure proteins (4 polypeptides)
- Secreted by B lymphocytes e.g. plasma cells in response to specific antigens
- Bind specifically to antigens forming antigen antibody complexes
Describe the structure of an antibody (8)
Antigen
Antigen binding site
Variable region
Constant region
Disulfide bridges
Light chain
Heavy chain
Hinge region
Explain how antibodies lead to the destrution of pathogens? (5)
- Antibodies bind to antigens on pathogens forming an antigen-antigen complex
-Specific tertiary structure so binding site/variable region binds to complemntary antigen
*Each antibody binds to 2 pathogens at a time causing agglutination(clumping) of pathogens - Antibodies attract phagocytes
- Phagocytes bind to the antibodies and phagocytose many pathogens at once
Explain the diff between primary anf secondary immune response (7)
- Primary-First exposure to antigen
-Antibodies produced slowly at a lower conc
-Takes time for specific plasma B cells to be stimulated to produce specific antibodies
-Memory cells produced - Secondary-Second exposure to antigen
-Antibodies produced daster and at a higher conc
-B memory cells rapdi;y undergo mitosis to produce many plasma cells which produce specific antibodies
Describe how agglutination occurs
Antibodies are flexible and can bind to two antigens and it clumps them together–>Making it easier for phagocytes to locate and destroy the pathogens
q
How does the body identify whether a cell is a self or non self cells
Lymphocytes do the job which are made when you are a foetus
Why are there little to no amounts of Self lymphocytes
- The lymphocytes complemntary to the antigens on a self cell will die or be surpressed
- This is done to prevent lymphocytes from attacking your own cells
Any new self lymphocytes made will be destroyed
What happens when the process of self lymphocytes being destroyed stops working
An autoimmune disease will occur as lymphocytes will attack self cells
What happens when there is a mutation in the gene which codes for an antigen
The pathogens DNA will mutate which changes the shape of the antigen—>Any previous immunity to this pathogen is no longer effective as the memory cells of the previous pathogen would have a diff shape
antigen variability
Give an example of antigen variability
Every year the influenza virus mutates and changes its antigens which iswhy a new vaccine is needed every year
