Any disease = interaction between pathogen and body's various defence mechanisms.
Having overwhelmed a pathogen, the body's defences are better prepared for a second infection from same pathogen, can repel it before it causes harm = immunity.
Those in ill health, the young and the elderly are usually more vulnerable.
Two main types:
- Non-specific mechanisms = don't distinguish between one type of pathogen and another, respond to all in the same way and act immediately. Take two forms: a) Barrier to entry of pathogens e.g. skin or b) phagocytosis.
- Specific mechanisms = distinguish between different pathogens, responses are less rapid but provide long-lasting immunity, involved type of white blood cell called lymphocyte, takes two forms: a…