Immune System Flashcards
How do cytotoxic T-cells work?
Attach to the foreign antigens on an infected cell. They then secrete perforin into the cell, a protein that makes holes in the cell-surface membrane and leads to cell death
What are the 4 types of T-cell?
- helper T-cells
- cytotoxic T-cells
- memory T-cells
- regulatory T-cells
What are the roles and features of plasma B-cells?
- only last a few days
- responsible for primary immune response
- secrete antibodies into plasma (around 200/sec)
What is the second line of defence against pathogens?
Non-specific inflammatory response, involving phagocytes and lysosomes
What is agglutination?
The process of a network of antibodies and particles clumping together due to the fact that antibodies have two sites where they can bind.
What is a macrophage?
A type of antigen presenting cell most commonly found in inflammatory sites
What is an example of indirect monoclonal antibody therapy?
T-DM1 is being trialled in the treatment of breast cancer. Involves trastuzumab, emtansine and a third component ensuring the drug remains inactive until it binds
What are the four ways that vaccines are made (fairly) harmless?
- Killing the pathogen while leaving antigens unaffected
- Using bacterial toxins that are milder, rather than using the pathogen itself
- Weakening the pathogen while leaving antigens unaffected
- Using genetically engineered cells to produce a microbial protein
What are the two types of active immunity?
Natural - from exposure to the disease
Artificial - from vaccination
What is the third line of defence against pathogens?
Specific immune response involving lymphocytes
What is the structure of an antibody?
Y-shaped molecule with two long and two short polypeptide chains. Disulphide bridges hold the polypeptide chains together. Variable regions on the top of each ‘Y’ point, that bind with each specific antigen
What are the two ways to obtain passive immunity?
- Through a mother’s breastmilk
- Directly given short-term antibodies e.g. anti-venom
What are the key features of a neutrophil?
- can move into other tissues by squeezing through capillary wall gaps
- cytoplasm that is full of lysosomes
- cell surface membrane covered in protein receptors
What four roles do helper T-cells play?
- stimulate division of B-cells in clonal selection
- activate cytotoxic T-cells
- increase rate of phagocytosis
- develop into memory cells
How does HIV cause symptoms of AIDS?
The take over of the T-helper cells results in them all dying. This means that there is no immune response, allowing opportunistic diseases to infect the person and all pathogens make the person feel unwell, causing the flu-like symptoms
What is active immunity?
When the body responds to an antigen by producing specific antibodies and memory cells, and direct exposure is required
What is passive immunity?
When the body is given antibodies with no exposure to the pathogen
What role do surface proteins play in the immune response?
Allow the body recognise cells as ‘self’ or ‘non self’, so the antibodies know which cells to attack
Why may vaccines not work or be suitable?
- impaired immune system so no response is produced
- contracting the disease before vaccination has developed
- antigen variability
How can agglutination assist in destroying pathogens?
- neutralise the pathogen by preventing them from being able to divide and develop
- attract phagocytes by acting as a ‘marker’, making them more visible to phagocytes
How does a prostate specific antigen test work?
1) Antibodies specific to PSA are bound to the surface of the test
2) Blood sample is added and any antigens present will bind to the antibodies
3) Secondary antibody with enzyme attached added that only binds to primary antibody is antigen is present
4) Complementary substrate added, which the enzyme reacts with to form a coloured product
What are the stages of phagocytosis?
1) Chemotaxis - chemicals released by pathogens cause phagocytes to move towards
2) Adhesion - receptors on surface of phagocytes attach to the chemicals on pathogen surfaces
3) Ingestion - phagocytes ingest the pathogen and form a membrane-bound vesicle (aka phagosome)
4) Digestion - lysosomes fuse with the phagosome and release the lysozymes, which hydrolyse the pathogen
What is an example of direct monoclonal antibody therapy?
Trastuzumab in the treatment of breast cancer
What is an antigen-presenting cell?
An immune cell that recognises pathogens, then engulfs them through phagocytosis and presents the pathogen’s antigens on the surface of their own cell, activating the T-cells
What are the main structures found in HIV and their roles? (6)
Reverse transcriptase - catalyses production of DNA from RNA
Attachment proteins - used to bind to host cell
Capsid - protein coat that protects the RNA
Lipid envelope - surround the cell
Matrix - inner proteins that link envelope with the core
RNA strands - genetic information
What is an antigen?
A molecule that stimulates an immune response, including antibody generation, such as proteins, glycoproteins and lipoproteins
Why do genetic mutations mean we can catch colds every year?
Genetic mutations cause antigen variability on the pathogen’s surface, meaning that memory B-cells are not activated
What is the process of clonal selection?
1) Surface antigens from a pathogen enter B cells through endocytosis
2) B cells process the antigens and display them
3) Helper T cells stimulate B cells to divide rapidly
4) B cells divide through mitosis
5) Plasma and memory cells are produced, all clones of the original B cell
What is the clonal selection theory?
The complementary B-cells are activated by the helper T-cells, so only the desired antibodies are cloned
What is formed when an antigen binds with a complimentary antibody?
Antigen-antibody complex
What is direct monoclonal antibody therapy?
When the antibody attaches directly onto cancer cells and block chemical signals that stimulate the uncontrolled growth, preventing it from dividing and eventually killing the cancer
What is a monoclonal antibody?
An identical clone of a plasma cell
What is the process of the cellular immune response?
1) Antigen presenting cells present the pathogen’s antigens on their cell surface membrane
2) Complementary T-cell receptors fit directly onto the antigens
3) This attachment stimulates the T-cell to divide rapidly
4) Cloned T-cells can develop into any of the 4 types of T cell
How do antibiotics work and why do they not work against HIV?
Antibiotics work by inhibiting the synthesis and assembly of cell walls in bacteria, along with disrupting the metabolic process. As HIV is acellular and invades body cells, there is nothing to disrupt.
How does HIV infect cells?
1) Attaches to the surface of a T-helper cell, releasing it’s RNA through fusing with the cell membrane
2) Reverse transcriptase from HIV converts the virus’ RNA to DNA
3) Virus DNA moves into the nucleus and becomes inserted in
4) Virus DNA creates mRNA using the cell’s own enzymes
5) mRNA passes out of the nucleus and uses the cell’s protein synthesis mechanisms to make new HIV viruses
6) New HIV viruses are released from the cell with a piece of the cell’s membrane surrounding it, forming the lipid envelope
What is an antibody?
A protein released by a B-cell in response to a non-self antibody
What does ELISA stand for?
Enzyme-linked immunosorbent assay
How is herd immunity obtained?
When most of the population is vaccinated, preventing spread to those who are more vulnerable to the diseases
What does the release of histamine do?
Makes the capillary walls more permeable, so that the neutrophils can reach the damaged area. This also means that more fluid goes to the area, causing localised swelling and redness.
What are the roles and features of memory B-cells?
- responsible for secondary immune response
- last in blood and tissue fluid until activated by pathogen
- if same antigen is recognised again, they divide rapidly, resulting in more antibodies quicker, destroying the pathogen before disease
What is indirect monoclonal antibody therapy?
When a radioactive or cytotoxic drug is attached to the antibody, which then passes it into the cancer cel when it binds to the cell
What is the first line of defence against pathogens?
Physical barriers e.g. skin, membranes, saliva
What type of immunity are T-cells responsible for?
Cell-mediated immunity
