Biology / Unit 10: Human Body Systems
10.6 The Immune System
Notes
The immune system defends the body against pathogens (disease-causing bacteria, viruses, fungi and parasites).
- First line (nonspecific): barriers such as skin, mucus, tears and stomach acid.
- Second line (nonspecific): inflammation, fever, and white blood cells (phagocytes) that engulf invaders.
- Third line (specific): lymphocytes target particular antigens (markers on pathogens).
- B cells make antibodies that bind to antigens. T cells help coordinate the response and kill infected cells.
- Memory cells remember a pathogen, so a second infection is fought off faster. This is immunity.
- Vaccines contain weakened, killed or partial pathogens (or instructions to make an antigen), so the body makes memory cells without getting sick.
Practice
What is the first line of defense against pathogens?
Physical and chemical barriers keep most pathogens out.
How does a vaccine protect a person from a disease?
Memory cells allow a fast response if the real pathogen appears.
Which cells make antibodies?
B cells produce antibodies that bind to specific antigens.
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