Non-specific defences work the same way against any germ, while specific defences target one particular germ. To sort a defence, ask whether it needs to recognise one particular antigen.
This lesson opens the cluster on immunity. The next lesson follows the specific response step by step.
What is the two-question test?
- Does it work against any pathogen in the same way? If yes, it is non-specific.
- Does it need to recognise one particular antigen? If yes, it is specific.
A defence cannot be both. The test is about how the defence finds its target, not where in the body it happens.
Worked example with six defences
Question: Sort these into non-specific and specific defence: skin, mucus in the airway, phagocytes, antibodies, stomach acid, lymphocytes that recognise one antigen.
| Defence | Test result | Group |
|---|---|---|
| Skin | Blocks any germ | Non-specific |
| Mucus in the airway | Traps any germ | Non-specific |
| Phagocytes | Engulf many kinds of germ | Non-specific |
| Stomach acid | Kills many kinds of germ | Non-specific |
| Antibodies | Match one antigen | Specific |
| Lymphocytes | Recognise one antigen | Specific |
Take an invented germ that enters through a cut. The skin barrier is broken, so phagocytes arrive first. Lymphocytes then recognise the germ’s antigen and start making antibodies.
Written answer: “Skin, mucus, stomach acid and phagocytes are non-specific because they act against many kinds of germ. Antibodies and lymphocytes are specific because each recognises one antigen.”
The mistake that loses marks
The common slip is to treat all white blood cells as specific, as in “Phagocytes are specific because they are white blood cells.” The test is about recognition, not cell type.
| Claim | Correct? | Fix |
|---|---|---|
| “Phagocytes are specific” | No | They engulf many germs, so non-specific |
| “Lymphocytes are specific” | Yes | Each recognises one antigen |
The fix is to ask the two questions before writing the group.
A routine for any defence
- Name the defence in one word.
- Ask whether it acts on any germ or one antigen.
- Write the group and the reason.
- If the question asks for order, put non-specific first and specific second.
The biological data interpretation trainer gives you practice reading timelines of the two responses.
Check yourself
Sort and give a reason: (a) tears containing an enzyme that breaks down bacteria, (b) an antibody that binds only to one virus surface protein.
Answer
(a) is non-specific, because the enzyme acts on many kinds of bacteria. (b) is specific, because the antibody binds only to one antigen.
What to study next
Go on to explaining antigen-antibody responses, where you follow the specific response step by step. For the blood cells involved, see transport in humans and animals.
If you want a teacher to test your sorting, see online one-to-one Biology tuition.