AP Biology - Plants and Human Body Systems
OpenStax Biology for AP — Chapter 33: The Immune System — AP BIOLOGY Revision Notes & Topical Questions
5 min read 7 parts Lesson 14 of 15 Unit quiz
Lesson summary
OpenStax Biology for AP — Chapter 33: The Immune System — AP BIOLOGY notes: Describe innate and adaptive immunity, antibodies, immunological memory, vaccination and disruptions of the immune system.Innate defences respond the same way to all pathogens, act quickly and have no mem…
- Cellular and molecular defences
- Clonal selection
- Active immunity
- Passive immunity
- Memory cell
- Cytotoxic T cell
Section 1 of 7Innate (nonspecific) defences
1
Innate defences respond the same way to all pathogens, act quickly and have no memory.
2Barriers
- Barriers skin, mucus, stomach acid and lysozyme.
3Cellular and molecular defences
- Cellular and molecular defences inflammation, fever, phagocytes, natural killer cells, cytokines and complement proteins.
4
If innate mechanisms fail, the adaptive response is informed and mobilised.
Section 2 of 7Adaptive (specific) immunity
The adaptive response is slower, longer lasting and directed at a particular antigen.
Antigen-presenting cells show antigens on MHC molecules to naive T cells, which become helper T cells or cytotoxic T cells.
Helper T cells release cytokines and stimulate B cells.
B cells differentiate into plasma cells that secrete antibodies.
Cytotoxic T cells kill infected or cancerous cells by inducing apoptosis.
Clonal selection
- Clonal selection the antigen selects lymphocytes with matching receptors, which divide to form effector cells and memory cells.
Section 3 of 7Antibodies
1
Antibodies (immunoglobulins) are secreted by plasma cells and mediate the humoral response.
2
There are five classes, and the class determines mechanism of action but not binding specificity.
3
Antibodies bind antigens through variable domains.
4
They neutralise toxins and pathogens, mark pathogens for phagocytosis and activate complement.
Section 4 of 7Memory and vaccination
Memory B and T cells give a faster, larger secondary response on re-exposure to the same antigen.
Vaccines expose the immune system to a harmless form of an antigen so memory cells form without disease.
Active immunity
Active immunity making your own antibodies.
Passive immunity
Passive immunity receiving antibodies from outside, such as from the mother.
Herd immunity protects those who cannot be vaccinated, and fast-mutating viruses such as influenza need updated vaccines.
| Feature | Primary response | Secondary response |
|---|---|---|
| Speed | Slow (days) | Fast |
| Antibody level | Low | High |
| Memory cells | Formed | Used and increased |
Section 5 of 7Disruptions of immunity
1
Allergies are exaggerated responses to harmless antigens.
2
Autoimmune diseases occur when the immune system attacks self, possibly through molecular mimicry.
3
Immunodeficiency increases susceptibility to infections and cancers.
4
HIV destroys helper T cells, which weakens both antibody and cytotoxic responses.
Section 6 of 7Key terms
| Term | Meaning |
|---|---|
| Antigen | Molecule that triggers an immune response. |
| Antibody | Protein secreted by plasma cells that binds a specific antigen. |
| Clonal selection | Selection and proliferation of lymphocytes with matching receptors. |
| Memory cell | Long-lived lymphocyte giving a faster secondary response. |
| Cytotoxic T cell | T cell that kills infected body cells. |
| Vaccine | Harmless antigen preparation that induces memory cells. |
Section 7 of 7Exam technique
Avoid these mistakes
Calling antibody production nonspecific — it is part of specific immunity
Saying memory cells prevent all later infections — they protect only against the same antigen, not different strains
Forgetting that cytotoxic T cells kill infected cells directly
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