5.1 - Defence mechanisms Flashcards
What is an infection
An interaction between the pathogen and the body’s various defence mechanisms
What are the 2 types of defence mechanisms
- non specific (skin or phagocytosis)
- specific (cell-mediated response or humoral response)
which lymphocyte is involved in cell-mediated response and which one is involved in humoral immunity
- cell-mediated responses involve T lymphocytes
- humoral responses involve B lymphocytes
What are self cells
The body’s own cells and molecules
What are non-self cells
Cells or molecules that are foreign
Why is it important that the immune system can tell the difference between self cells and non-self cells
- defend from foreign materials
- not destroy the organism’s own tissues when defending itself
Give examples of non-self cells
- pathogens, e.g. HIV
- Non-self material, such as cells from other organisms of the same species
- Toxins, including those produced by certain pathogens
- Abnormal body cells, such as cancer
What is the problem with organ/tissue transplants in humans, how can we solve this?
- The immune system recognises the transplant as non-self and begins to attack the transplanted tissue
SOLUTIONS: - tissue matching (e.g. from relatives)
- immunosuppressant drugs
Describe how lymphocytes are able to identify cells as ‘self’ or ‘non-self’
- lymphocytes have receptors that exactly fit those of the body’s own self cells
- these lymphocytes are destroyed/suppressed
- only ones that stay are the ones that fit foreign material (non-self)
Explain what the most important molecule in the immune system is
- protein
- Antigens are made of proteins
- this is something the whole immune system relies on
What are the 4 things that the immune system can identify
- pathogens
- non-self material
- toxins
- Tumors
When are specific lymphocytes produced in order to fight infection
- they’re not produced in response
- they’re already existing in the blood (ten million different types - at least one will recognise the pathogen)
What happens when an infection occurs, and the one type of lymphocyte already present has the complimentary proteins to those of the pathogen
- the lymphocyte is stimulated to divide
- so that it can build up its numbers to a level where it can be effective in destroying it (clonal selection)
—> it explains the time lag between exposure to pathogen and the body’s defences bringing it under control
How do lymphocytes recognise the cells that belong to the body
- in a fetus, the lymphocytes are constantly colliding with cells
- infection in the foetus is rare due to the placenta protecting it, therefore the lymphocytes only collide with self cells
- some of the lymphocytes will have complimentary receptors for those of the body’s own cells
- these lymphocytes then die or are suppressed, therefore only remaining lymphocytes will only fit and respond to foreign material
Where are lymphocytes are produced in adults
- bone marrow (initially only encountering self-antigens)
- any lymphocytes that show an immune response to these self-antigens and undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes
- therefore no clones of these anti-self lymphocytes will appear in the blood, leaving only those that might respond to non-self antigens
