3.6.6Additional lessons
Adaptive Immune Response — IB Biology SL Revision Notes & Topical Questions
5 min read 5 parts Lesson 75 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Antibodies
Structure
- Structure Antibodies are Y-shaped proteins made of four polypeptide chains, with two identical antigen-binding sites at the tips.
Variable region
- Variable region The shape of the binding site differs between antibodies, which makes each one specific to a single antigen.
Constant region
- Constant region The stem is similar in the same class of antibody and helps to attract other immune cells.
Actions
- Actions Antibodies neutralise pathogens or toxins, cause pathogens to clump together, and mark them for phagocytes.
Part 2 of 5Clonal Selection
The body selects the lymphocytes that already fit the antigen and multiplies them.
1
A pathogen enters and its antigens are taken up and displayed by an antigen-presenting cell.
2
Only the few T and B cells with receptors complementary to that antigen are selected.
3
Selected cells divide repeatedly by mitosis to form a large clone of cells with identical receptors.
4
Most B cells differentiate into plasma cells that secrete large quantities of the same antibody.
5
A smaller number become memory cells that stay in the body after the infection.
Part 3 of 5Primary and Secondary Responses
Primary and Secondary Responses
Primary response
- Primary response The first exposure produces few antibodies slowly, so symptoms of the disease may appear.
Secondary response
- Secondary response A later exposure produces antibodies sooner, in larger amounts and for longer.
Cause of the difference
- Cause of the difference Memory cells already exist for the antigen, so less time is needed to select and multiply cells.
Result
- Result The infection is cleared before symptoms occur and the person is immune.
| Feature | Primary | Secondary |
|---|---|---|
| Lag time | Longer | Shorter |
| Peak antibody level | Lower | Higher |
| Memory cells present | No | Yes |
Part 4 of 5Cell-mediated Response
Cytotoxic T cells
- Cytotoxic T cells They recognise infected cells and kill them, which is important in defence against viruses.
Helper T cells
- Helper T cells They release chemical signals that stimulate B cells and other immune cells.
Control
- Control Once the pathogen is cleared, most effector cells die and the response subsides.
Part 5 of 5Exam Checklist & Tips
3.6.6 – Key Points for the Exam
- Antibody A Y-shaped protein made by plasma cells that binds a specific antigen.
- Clonal selection Selection and multiplication of lymphocytes that match an antigen.
- Plasma cell A B cell that secretes antibodies.
- Memory cell A cell that remains after infection and responds quickly to re-exposure.
Common Mistakes
- Writing that antibodies are made by T cells, when plasma cells (from B cells) make them.
- Saying the body makes new lymphocytes for each pathogen from nothing, when it multiplies ones that already fit.
- Mixing up antigens and antibodies.
- Believing the secondary response is the same size as the primary response.
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