Disease and Immunity
IGCSE (Year 10โ11) ๐ซ Physiology & Health Pathogens, immune response, vaccines, antibiotics.
๐ก๏ธ The Immune Response
The immune system distinguishes between self (body's own cells) and non-self (pathogens, infected cells) by recognising antigens.
- Non-specific defences: skin, mucus + cilia, stomach acid, inflammation, fever
- Phagocytes (neutrophils, macrophages) โ engulf and digest pathogens (phagocytosis); present antigens on surface
- B lymphocytes โ activated by antigen โ differentiate into plasma cells (produce antibodies) and memory B cells
- T lymphocytes โ T helper (coordinate response), T killer (destroy infected cells)
- Memory cells โ long-lived; enable rapid secondary immune response if same antigen encountered again
๐ก๏ธ Vaccines and Immunity
| Active immunity | Passive immunity | |
|---|---|---|
| How obtained | Own immune system produces antibodies (infection or vaccination) | Antibodies received from another organism |
| Speed | Slow to develop | Immediate |
| Duration | Long-lasting (memory cells) | Short-lived (antibodies degrade) |
| Examples | MMR vaccine, having chickenpox | Maternal antibodies in breast milk; antiserum injection |
How vaccines work
Antigen introduced (dead/weakened pathogen or surface protein) โ B cells activated โ antibodies + memory cells formed โ real infection triggers rapid secondary response before disease develops๐ก๏ธ Monoclonal Antibodies
- Produced by fusing an antibody-producing B lymphocyte with a myeloma (cancer) cell โ hybridoma cell
- Hybridoma divides indefinitely producing identical (monoclonal) specific antibodies
- Uses: pregnancy tests (hCG detection), cancer diagnosis/treatment (target therapy), ELISA (diagnostic assays)
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