Biology · Both
Pathogens & Immunity
Types of pathogen, how disease spreads, immune response, vaccination and antibiotics.
Pathogens are microorganisms that cause disease. The body has defences, and vaccination helps prevent infection. Antibiotics treat bacterial infections only.
Types of pathogen
• **Bacteria** – e.g. Salmonella, tuberculosis
• **Viruses** – e.g. influenza, HIV, measles (reproduce inside host cells)
• **Fungi** – e.g. athlete’s foot
• **Protists** – e.g. malaria (Plasmodium)
Transmission: air (droplets), water, contact, vectors (e.g. mosquitoes), contaminated food.
Immune response
White blood cells:
• **Phagocytes** – engulf and digest pathogens
• **Lymphocytes** – produce **antibodies** that bind to specific antigens; some become memory cells
**Vaccination** – introduces a safe form of the pathogen (dead, weakened or antigen only).
Body produces antibodies and memory cells → faster response if infected later (immunity).
Herd immunity protects those who cannot be vaccinated.
Antibiotics and painkillers
• **Antibiotics** kill bacteria or stop them growing – **do not work on viruses**
• Overuse can lead to antibiotic-resistant bacteria
• Painkillers (e.g. paracetamol) relieve symptoms but do not kill pathogens
Practice questions
Try these without looking at the answers first.
Q1.Do antibiotics kill viruses?
Show answer
No
Q2.What do lymphocytes produce?
Show answer
Antibodies
Q3.What is a vaccine?
Show answer
Safe form of pathogen that triggers immunity / memory cells