BRAINCAKEThe Immune System
The immune system is the body's defence against pathogens. Pathogens are microorganisms that cause disease and can be viruses, bacteria, fungi or protoctists.
When the pathogens gain entry into the body, they rapidly multiply in number, using the body's resources. They destroy cells or produce toxins which are metabolites that interfere with the body's cellular activities.
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Key terms in this lesson
- tissue fluid
- The fluid, formed by the filtration of blood plasma under hydrostatic pressure, that surrounds cells and supplies them with substances.
More in Cell Recognition and the Immune System
- Defence Mechanisms
- Lymphocytes and Phagocytes
- Recognising Self and Non-Self Cells
- Phagocytosis
- Antigens
- Lymphocytes
- Cell-Mediated Immunity
- Cytotoxic T-cells
All 30 lessons in Cell Recognition and the Immune System · All AQA AS-level Biology topics