T cells and cell-mediated immunity Flashcards
(25 cards)
What is an antigen?
An antigen is any part of an organism or substance that is recognised as non-self (foreign) by the immune system and stimulates an immune response
What are antigens usually part of ?
Antigens are usually proteins that part of the cell-surface membrane or cell walls of invading cells, such as microorganisms or diseased cells
What does the presence of an antigen trigger?
The presence of an antigen triggers the production of an antibody as part of the body’s defence system
What are immune responses such as phagocytosis?
Immune responses such as phagocytosis are non-specific
What other responses does the body have to infection?
The body also has specific responses that react to individual forms of infection
What is different about a specific response?
- Specific responses are slower in action at first, but can provide long-term immunity
What does a specific immune response depend on?
A specific immune response depends on a type of white blood cell called a lymphocyte
What does an antigen trigger the production of?
An antigen generates the production of an antibody
How many types of lymphocytes are there?
Two types of lymphocyte:
- B lymphocytes - associated with humoral immunity, ie immunity involving antibodies that are present in body fluids, or ‘humour’
- T lymphocytes - associated with cell-mediated immunity
What type of immunity are T lymphocytes associated with?
T lymphocytes are associated with cell mediated immunity
Where are T lymphocytes formed of?
T lymphocytes are formed from stem cells found in the bone marrow
Where do T lymphocytes develop?
T lymphocytes develop in the Thymus gland
What do T lymphocytes respond to?
T lymphocytes respond to an organism’s own cells that have been invaded by non-self material, eg. a virus or cancer cell
What else do T lymphocytes respond to?
T lymphocytes also respond to transplanted material, which is genetically different
How can T lymphocytes distinguish invader cells?
- Phagocytes that have engulfed and broken down a pathogen present some of the pathogen’s antigens on their own cell-surface membrane
- Body cells invaded by a virus also manage to present some of the viral antigens on their own cell-surface membrane as a sign of distress
- Cancer cells also present antigens on their cell-surface membranes
What are these cells called?
These cells are called antigen-presenting cells because they can present antigens of other cells on their own cell-surface membrane
Why is this cell-mediated immunity?
This is cell-mediated immunity as the T lymphocytes will only respond to antigens that are attached to a body cell (rather than cells within the body fluids?
What are the stages of a T lymphocytes response to infection by a pathogen?
1) Pathogens invade body cells or are taken in by phagocytes
2) The phagocyte places antigens from the pathogen on its cell-surface membrane
3) Receptors on certain T helper cells fit exactly onto these antigens
4) This activates other T cells to divide rapidly by mitosis and form a clone
5) The cloned T cells:
- develop into memory cells that enable a rapid response to future infections by the same pathogen
- stimulate phagocytes to engulf pathogens by phagocytosis
- Stimulate B cells to divide
- kill infected cells
How do T cells kill infected cells?
T cells kill body cells that are infected by pathogens
- They produce a protein which makes holes in the cell-surface membrane, causing the cell to become freely permeable to all substances, causing the death of the cell
What are T cells most effective against?
T cells are most effective against viruses because they live inside cells
State two similarities between T cells and B cells
- Both are formed of stem cells from the bone marrow
- Both have a role in immunity
- Both are types of white blood cell
State two differences between T cells and B cells
- T cells develop in the thymus gland, whilst B cells develop in the bone marrow
- T cells are involved in cell-mediated immunity, whilst B cells are involved in humoral immunity
What is an antigen?
An antigen is an organism recognised as foreign by the immune system and therefore stimulates an immune response
How can a H5N1 infection lead to suffocation?
H5N1 infects the lungs and triggers a massive production of T cells. Accumulation of these cells may block the airways and fill the alveoli, causing suffocation
