These questions ask you to follow two connected systems: immune recognition and defence, and the movement and filtering of lymph. Work from the clue in the prompt to the process, cell, molecule, fluid, or organ that has that exact role.
Trace the defence route
Begin by classifying the clue. A fast response aimed broadly at types of danger belongs to innate defence. A response aimed at a particular antigen, especially one that can leave immunological memory, belongs to adaptive defence. Both are selective enough to protect the body without normally treating its own cells as foreign. Next ask which worker is involved. B lymphocytes can become plasma cells, which release antibodies. An antibody attaches when its binding site complements a region of an antigen. T lymphocytes have several roles: some coordinate other immune activity, while others destroy certain infected or abnormal body cells.
| Clue to follow | Route or structure to identify |
|---|---|
| Rapid and broadly directed | Innate defence is already available and is not tailored to one unique antigen. |
| Particular antigen and later memory | Adaptive defence uses specific recognition and can retain memory. |
| Tissue fluid enters a lymphatic vessel | It is now lymph; the vessel network eventually returns excess fluid to the circulation. |
| Filtering named by fluid | A lymph node filters lymph, whereas the spleen filters blood. |
| Developing T lymphocytes | Their maturation site is the thymus. |
Use a three-pass check: identify the material being followed, note its direction, then match the stated action. For fluid, trace tissue spaces to lymphatic vessels and onward to the bloodstream. For an organ, the named fluid or developmental stage matters more than the general fact that several organs support immunity.
Common wrong turns
| Tempting shortcut | How to reject it |
|---|---|
| Treating immune defence as an attack on everything | Recognition must distinguish many threats and abnormal cells from the body's own cells; oxygen transport is not its main task. |
| Calling a specific response with memory innate | Specific recognition plus memory identifies the adaptive branch. Innate defence is the rapid, broadly directed branch. |
| Assuming one antibody binds everything or digests whole cells | Binding depends on complementary regions. Specific attachment is different from indiscriminate digestion. |
| Calling lymph whole blood or treating lymphatic vessels as storage | Lymph begins as tissue fluid entering lymphatic vessels, and the network provides a return path rather than a permanent reservoir. |
| Matching an organ by the word immune alone | Match the precise job: nodes filter lymph, the spleen filters blood, and the thymus supports T-lymphocyte maturation. |
Try it
Which features correctly classify innate immunity? Select all that apply.
- It can respond rapidly
- It forms only after repeated exposure
- It uses broadly directed defences
- It recognizes just one unique antigen
Which roles are performed by at least some T lymphocytes? Select all that apply.
- Carry lymph by pumping vessels
- Coordinate immune responses
- Secrete all circulating antibodies
- Destroy certain infected body cells
Reverse lookup: which organ filters blood and supports immune responses to material carried in that blood?
- Thymus
- Lymph node
- Spleen
- Diaphragm