Topic 2.3 - Cell Recognition And The Immune System Flashcards
(40 cards)
What is a pathogen?
A pathogen is an organism that causes disease to its host.
What is an infection?
The interaction between the pathogen and the body’s various defence mechanisms.
What is immunity?
Preparing the body’s defences for a second infection from the same infection, to kill it before it can cause any harm.
What is the white blood cell used for defences called?
A lymphocyte.
What are the two types of lymphocytes and what kind of responses do they have?
- T-lymphocytes that are involved in cell-mediated response.
- B-lymphocytes that are involved in humoral response.
Give 4 examples of non-self cells that can trigger an immune response.
- Pathogens such as HIV.
- Cells from other organisms of the same species.
- Toxins, including those from certain pathogens.
- Abnormal cells, such as cancer cells.
What are the 2 types of defence mechanisms?
Specific and non-specific.
What is the difference between non-specific and specific defence mechanisms?
Specific is slower and targeted to each pathogen, however non-specific is immediate and me same for all pathogens.
Give 2 examples of non-specific response.
- Physical barriers such as skin.
- Phagocytosis.
Give 2 examples of specific response.
- Cell-mediated response.
- Humoral response.
What is the difference between a phagocyte and a lymphocyte?
A phagocyte engulfs and digests the pathogen in a process called phagocytosis. This is done before it can cause harm. Lymphocytes are involved in immune responses. Phagocytes are a non-specific defence mechanism as opposed to lymphocytes that apart of the specific defence mechanism.
What is the process for phagocytosis?
Chemical products of pathogens or dead, damaged and abnormal cells act as l attractants, causing phagocytes to move towards these cells.
Phagocytes have many receptors on their cell-surface membrane which attach to the chemicals on the pathogens.
The phagocytes then engulf the pathogen and form a vesicle around mean called a phagosome.
The phagocyte contains lysosomes which fuse with the phagosome to form a phagolysosome.
The lysosomes have hydrolyticenzymes which hydrolyse (digests) the pathogens.
The cytoplasm of the pathogen then absorbs the soluble products from the breakdown of the pathogen.
The phagocyte then presents the antigens from the pathogen on its cell- surface membrane.
What is an antigen?
A part of an organism that is recognised as non-self by the immune system and stimulates an immune response.
Why are T-lymphocytes called T-lymphocytes?
They are T because they mature in the thymus gland.
What happens in cell-mediated response?
Phagocytes that have the antigens presented on their cell-surface membrane can have 3 complementary cells bound to them (B-lymphocytes, T-lymphocytes and Helper T cells).
The helper T cells secrete cytokines which activate the B and T cells.
The T cells are then activated and clone by mitosis to form genetically identical cells.
The cloned tells can:
1. Develop into memory cells for a rapid response to future infections.
2. Stimulate phagocytes to undergo phagocytosis.
3. Stimulate B cells to divide and secrete their antibodies.
4. Activate cytotoxic T cells.
What do Cytotoxic T cells do?
They kill abnormal and body cells that are infected by pathogens by producing a protein called perform which creates holes in the cell-surface membrane. This allows the membrane to become freely permeable to all substances and the all dies as a result.
What happens in humoral response?
The surface antigens of a pathogen are taken up by a B cell.
The B cells process the antigens and present them on their surface. (clonal selection).
Helper T cells then attach themselves onto the antigens and activate the B cell.
The B cells then divide by mitosis to give a clone of plasma cells. (clonal expansion).
The cloned plasma cells then secrete antibodies that exactly fit the antigen of the pathogen and destroys them.
Some B cells can be developed into memory cells for future infections (secondary immune response).
What is the difference between plasma cells and memory cells?
Plasma cells secrete antibodies and so are short lived, memory cells can last decades and so are used in the secondary response.
If the question asks or mentions anything about antibodies, which response do you use?
Humoral.
If the question asks or mentions anything about the destruction of cells, which response do you use?
Cell-mediated.
How do antibodies lead to the destruction of antigens?
They cause agglutination of the bacterial cells, in this way clumps of bacterial cells are formed so the pathogens are less spread out.
They then serve as markers that stimulate phagocytes to engulf the cells.
What is a Monoclonal antibody?
A single type of antibody that can be cloned.
Give 3 uses for monoclonal antibodies.
- Targeting medication to specific cells.
- Medical diagnosis.
- Pregnancy testing.
How are Monoclonal antibodies used in targeting medication to specific cell types?
One way is to produce a monoclonal antibody that is specific to the antigens of a cell (e.g. a cancer cell). Then the antibodies are given to a patient and attach themselves to the receptor on their cancer cells. This then blocks the chemical signals that stimulate their uncontrolled growth preventing the cancer to spread further.
Another way is to attach radioactive or cytotoxic drugs to the antibody so that when it is attached onto the cell it kills them. This is known as indirect monoclonal antibody therapy.
