Defence mechanisms Flashcards
(18 cards)
What is an infection?
An infection is an interaction between the pathogen and the body’s various defence mechanisms
Millions of people die from infectious diseases but many also survive
For both of these scenarios, for an infected person, what happens inside the body involving the pathogen and the defence mechanisms?
When an individual dies from an infection, the pathogen has overwhelmed the defences which has caused the individual to pass
When the individual gets infected then recovers, this involves the defence mechanisms overwhelming the pathogen and the individual recovering from the disease
When an individual’s defence mechanisms overcome the pathogen what does this result in?
When the body’s defence mechanisms overwhelm the pathogen, they become better prepared for a second infection from the same pathogen and can kill it before it can cause harm. This is known as immunity
What type of people are least likely to be affected by an infection?
What type of people are more likely to be affected by infections?
A fit, healthy adult will rarely die to an infection
Those in ill health, the young and the elderly are usually more vulnerable to infections
What are the two types of defence mechanisms?
There are specific and non specific defence mechanisms
What are examples of specific defence mechanisms?
The cell mediated response, involving T lymphocytes
The humoral responses involving B lymphocytes
What are examples of non specific defence mechanisms?
Phagocytosis
Physical barriers like your skin
What must lymphocytes be able to do in order to defend the body?
Lymphocytes must be able to distinguish the body’s own cells and molecules (self cells) from those that are foreign (none - self cells)
If lymphocytes could not distinguish between self and non - self cells, what would happen?
Lymphocytes would damage the organism’s own tissues
What does each cell type have on it surface to identify it, whether non - self or self cells?
Non - self or self cells have antigen on their surface to allow you to identify it
What are antigens? What is their function?
Antigens are macromolecules, often proteins, unique to each cell and pathogen. They signal to the immune system whether a cell is “foreign” or “self”.
What are four things these antigens allow your immune system to identify?
1) Pathogens (human immunodeficiency virus)
2) Non - self material (cells from other organisms of the same species)
3) Toxins (bacterium that causes cholera)
4) Abnormal body cells (cancer cells)
Explain why tissue or organ transplants can be rejected by the recipient’s body?
When someone has had a tissue or organ transplant, the immune system recognises these as non - self even though they have come from individuals of the same species. this results in the immune system attempting to destroy the transplant.
Describe two ways in which the risk of rejection can be minimise?
To minimise the effect of tissue rejection, donor tissues for transplant are normally matches as closely as possible to those of the recipient. In addition, immunosuppressant drugs are often administered to reduce the level of immune response that still occurs
What happens to a lymphocyte when it has complementary proteins (antibodies) to a pathogen within the body?
When an infection occurs, the type of lymphocyte that has the complementary proteins to those of the pathogen is stimulated to divide to build up its numbers to a level where is can effectively destroy it.
This is known as clonal selection
How do lymphocytes recognise cells belonging to the body, when individuals are in the stage of early development?
During early development, lymphocytes are exposed to the body’s own cells. Any lymphocyte that responds to the body’s own antigens is either destroyed or suppressed
What is clonal deletion and what does it allow?
Clonal deletion is a process in the immune system that removes T and B lymphocytes that attack the body’s own cells.
This ensures remaining lymphocytes are tolerant to self antigen and do not attack the body’s own tissues
What occurs if clonal deletion does not occur properly?
If clonal deletion does not occur properly, lymphocytes which attack self - cells are produced, causing the symptoms of autoimmune diseases
