Pathogens are inhibited into entering into the body by various mechanisms such as:
- The eye has tears and eyelashes
- Respiratory system having mucus and cilia lining the tracts
- The skin is a physical barrier including antibacterial properties of sebum and sweat
The immune system is a collection of cells tissues and organs with mechanisms that defend an organism against the pathogen and other foreign substances. An immune system response in the body is a complex series of specific and non-specific processes involving a range of cells and chemicals.
- Non-specific immune response is the ‘general’ response to pathogen.
- For example the physical barriers such as the skin and mucus.
- Phagocytosis engulfs the pathogen regardless to what the pathogen is
- The response is immediate as they are always present
- Specific immune response is far flower however is unique to each pathogen
- Cell mediated response in the T-cells
- Humoral response in B-lymphocytes
- An antigen is any part of an organism or substance that is recognised as a non-self (foreign) by the immune system and stimulates an immune response
- Antigens are usually proteins that are part of the cell surface membrane or cell wall
- The presence of a non-self antigen causes the production of an antibody as part of the body’s defence system
- Lymphocytes are white blood cells
- They are produced by stem cells
- Matured in the bone marrow
- Produces antibodies and antitoxins
- Responds to foreign materials outside body cells
- Humoral immunity (immunity involving antibodies that are present in the body’s fluids (humour) such as blood plasma)
- Matured in the Thymus Gland
- Responds to antigens presented by the phagocytes
- Responds to viral infected cells and cancer
- Associated with cell mediated immunity (immunity that involves body cells)
How lymphocytes recognise cells belonging to the body:
- There are around 10 million different lymphocytes present at any time
- In the foetus, these lymphocytes are constantly colliding with other cells. However infection as a foetus is rare
- Lymphocytes will therefore collide almost exclusively with the body’s own material. Lymphocytes have receptors that exactly fit those of the body’s own cells.
- These lymphocytes either die or are suppressed whether leaving those that might fit foreign antigens and therefore only respond to the presence of foreign materials
- In adults lymphocytes are produced in the bone marrow only encounter self-antigens
- Any lymphocyte that shows an immune response to the self-antigens undergo programmed cell death (Apoptosis)