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Non-Specific Immune Response (Routes for Pathogen (Digestive system via…
Non-Specific Immune Response
Routes for Pathogen
Digestive system via contaminated food
Respiratory system by being inhaled
Cuts in the skin
Other mucosal surfaces (e.g. nose, mouth, genitals)
Barriers to Prevent Infection
Skin
Skin acts as a physical barrier to pathogens, but if the skin is damaged, pathogens can enter your bloodstream. Even if your blood then clots, some can get in before the clot appears.
Gut and Skin Flora
Intestines and skin are naturally covered in billions of harmless microorganisms called flora. They compete with pathogens for nutrients and space, limiting the number that can enter the body.
Stomach Acid
Most pathogen consumed through eating or drinking will be killed by the acidic conditions of the stomach
Lysozyme
Mucosal surfaces produce secretions (tears, saliva, mucus) that contain an enzyme called lysozyme. This kills bacteria by damaging their cell walls
Foreign Antigens
Antigens are molecules (usually proteins) found on the surface of cells. When a pathogen invades the body, the antigens on its cell surface are recognised as foreign which activates an immune response.
How it happens
Occurs in the same way for all microorganisms
Three ways of attacking the microorgansims
Inflammation
1) Immune system recognises foreign antigens and releases molecules that trigger inflammation
2) The molecules cause vasodilation (widening of blood vessels) around the infection site, increasing blood flow
3) The molecules also increase the permeability of the blood vessels
4) The increased blood flow brings loads of immune system cells to the infection site and the increased permeability allows these cells to move out of the blood vessels into the infected tissue
5) The immune system cells can start to destroy the pathogen
Phagocytosis and Lysozyme Action
A phagocyte (e.g. a macrophage) is a type of white blood cell that carries out phagocytosis (pathogen engulfment). They are the first cells to respond:
1) A phagocyte recognises the antigens on a pathogen
2) The cytoplasm of the phagocyte moves around the pathogen, engulfing it
3) The pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte
4) A lysozyme fuses with the vacuole and breaks down the pathogen
5) The phagocyte then presents the pathogen's antigens. It sticks antigens on its surface to activate other immune system cells
Production of Anti-Viral Proteins
When a cell is infected with viruses they produce proteins called interferons and they help to prevent the virus spreading to uninfected cells. They do this in several ways:
1) They prevent viral replication by inhibiting the production of viral proteins
2) They activate cells involved in the specific immune response to kill infected cells
3) They activate other mechanisms of the non-specific immune response (promote inflammation)