1. The Immune System What is a pathogen? Specification Point 3.4.2
Specification Point 3.4.2
Each type of cell has specific molecules on its surface that identify it. These molecules include proteins and enable the immune system to identify:
•• pathogens
•• cells from other organisms of the same species
•• abnormal body cells
•• toxins.
Definition of antigen. The effect of antigen variability on disease and disease prevention.
What is a pathogen?

2. Types of Response against Pathogens
Learning Outcomes:
Define the term antigen
Explain how cells of the immune system distinguish between self and non self.
Describe the likely process of how cells are able to develop and diferentiate between self and non self cells.
Types of Response against Pathogens
Immediate, non specific responses – natural barriers and Phagocytosis
Less Rapid more specific responses – Lymphocytes
Cell mediated response (Using T Lymphocytes)
Humoral response (Using B Lymphocytes)

3. Antigen Learning Outcomes: Define the term antigen
Explain how cells of the immune system distinguish between self and non self.
Describe the likely process of how cells are able to develop and diferentiate between self and non self cells.
Antigen
Any chemical substance which can provoke an immune response.
Chemical marker on the cells surface on the membrane. It identifies the cell.
White blood cells have the ability to recognise these antigens and respond appropriately.

4. Distinguishing between you and foreign particles
Learning Outcomes:
Define the term antigen
Explain how cells of the immune system distinguish between self and non self.
Describe the likely process of how cells are able to develop and diferentiate between self and non self cells.
Distinguishing between you and foreign particles
Foreign particles have different antigens to your own cells.
Mr Nash cells have Mr Nash Antigens.
Saab cells have Saab antigens.
Bacterial cells have their own bacterial antigens
When your cells come into contact with other bodies, they detect if the antigens are ‘self’ or ‘non self’.
If the antigens detected are ‘non self’, then an immune response is initiated.
Q: Why are organ donations/transplants rejected so often?

5. How cell recognition develops
Learning Outcomes:
Define the term antigen
Explain how cells of the immune system distinguish between self and non self.
Describe the likely process of how cells are able to develop and diferentiate between self and non self cells.
How cell recognition develops
Immature white blood cells are produced by the bone marrow in the fetus.
These cells have different receptors that can detect a huge variety of different antigens.
Whilst developing, they are exposed (only) to plenty of ‘self’ antigens.
If they come into contact with one of the ‘self’ antigens, then they interact and both the cell with this self detecting receptor and the antigen will die. This is called Apoptosis (programmed cell death)
Only cells with receptors that can don’t have self receptors survive and mature. (These ones can detect non self antigens)

6. Immature white blood cells are produced by the bone marrow.
These cells have different receptors that can detect a huge variety of different antigens.
Whilst developing, they are exposed to plenty of ‘self’ antigens.
If they come into contact with one of the ‘self’ antigens, then they interact and both the cell with this self detecting receptor and the antigen will die.
Only cells with receptors that can don’t have self receptors survive and mature. (These ones can detect non self antigens)

7. Non – Specific - Natural Barriers
12 P3 Fri
Learning Outcomes:
Define the term antigen
Explain how cells of the immune system distinguish between self and non self.
Describe the likely process of how cells are able to develop and diferentiate between self and non self cells.
Non – Specific - Natural Barriers

8. Non – Specific - Phagocytosis
Learning Outcomes:
Define the term antigen
Explain how cells of the immune system distinguish between self and non self.
Describe the likely process of how cells are able to develop and diferentiate between self and non self cells.
Non – Specific - Phagocytosis