Defence Mechanisms
Non-specific
-they do not distinguish between different types of pathogen so respond the same way to all of them
-this can be a barrier e.g. skin
-phagocytosis is also non-specific
Specific
-they distinguish between different pathogens.
-the response it less rapid, but provides long-lasting immunity.
-involve lymphocytes (a type of white blood cell)
-this could be a T lymphocyte (cell-mediated) or a B lymphocyte (humoral).
-they do not distinguish between different types of pathogen so respond the same way to all of them
-this can be a barrier e.g. skin
-phagocytosis is also non-specific
Specific
-they distinguish between different pathogens.
-the response it less rapid, but provides long-lasting immunity.
-involve lymphocytes (a type of white blood cell)
-this could be a T lymphocyte (cell-mediated) or a B lymphocyte (humoral).
Recognising Your Own Cells
-lymphocytes must be able to distinguish body cells/ chemicals from those of invading cells.
-if they didn't, they would attack the body's healthy tissues.
-if they didn't, they would attack the body's healthy tissues.
Controlling Infection
-lymphocytes are not produced in response to an infection.
-there are around 10 million different lymphocytes, so it is extremely likely that you will have a lymphocyte with a complimentary protein on its surface to a protein on an invading pathogen (recognition).
-there are only a few of each type, so when an infection occurs, the right lymphocytes must build up their numbers by mitosis (hence a lag time).
-there are around 10 million different lymphocytes, so it is extremely likely that you will have a lymphocyte with a complimentary protein on its surface to a protein on an invading pathogen (recognition).
-there are only a few of each type, so when an infection occurs, the right lymphocytes must build up their numbers by mitosis (hence a lag time).
Questions
1) State two differences between a specific and non specific defence mechanism. (2 marks)
2) After a pathogen gains entry to the body it is often a number of days before the body's immune system begins to control it. Why is this so? (2 marks)
3) Why is it wrong to say that the body takes a number of days to 'respond' to the pathogen? (1 mark)
2) After a pathogen gains entry to the body it is often a number of days before the body's immune system begins to control it. Why is this so? (2 marks)
3) Why is it wrong to say that the body takes a number of days to 'respond' to the pathogen? (1 mark)