Topic 6B - Infection And The Non-Specific Immune Response

Front 1

How can pathogens enter the body?

Back 1

Through cuts in the skin

Through the digestive system by food.

Through the respiratory system by inhalation.

Through mucosal surfaces e.g. nose, mouth.

Front 2

How does stomach acid prevent infection?

Back 2

If you eat or drink something that contains pathogens, most are killed by acidic conditions of the stomach. Some may survive and pass into intestines where they invade cells of the gut wall and cause infection.

Front 3

How does skin prevent infection?

Back 3

Your skin acts as a physical barrier to pathogens. If it's damaged, pathogens on the surface can enter your blood stream. The blood clots at the area to prevent pathogens from entering, but some may get in before the clot forms.

Front 4

How does your gut and skin flora prevent infection?

Back 4

Your intestines and skin are covered in harmless microorganisms (flora). They compete with pathogens for nutrients and space, limiting how many pathogens can live in the gut and on the skin, making it harder for infection.

Front 5

How do lysozymes protect from infection?

Back 5

Mucosal surfaces produce secretions, containing lysozyme, which kills bacteria by damaging their cell walls, making the bacteria lyse.

Front 6

How is an immune response triggered?

Back 6

The immune system is activated when antigens on the invading pathogens cell surface are recognised as foreign. Antigens are molecules found on the surface of cells.

Front 7

How is inflammation triggered, and what is it?

Back 7

Immune system cells recognise foreign antigens on the pathogen and release histamines which trigger inflammation. The molecules cause vasodilation, increasing the blood flow to it. Permeability also increases. This means loads of immune system cells arrive at infection site, so they can destroy the pathogen.

Front 8

What are interferons?

Back 8

1. Interferons are proteins which are produced when a cell becomes infected, which prevent viral replication by inhibiting production of viral proteins.
   
2. They activate T helper cells to kill infected cells.
   
3. They also promote inflammation to bring white blood cells to site of infection.
   

Front 9

What are the stages of phagocytosis?

Back 9

1. A phagocyte recognises antigens on a pathogen. It engulfs the pathogen via endocytosis. Pathogen is now in a phagocytic vacuole. A lysosome fuses with the vacuole and breaks down the pathogen.
   
2. The phagocyte presents the pathogen's antigens, activating other immune system cells, becoming a antigen-presenting cell.