Lesson 1 of 5 / Immune recognition and memory
Innate, adaptive, active and passive
Which distinction describes specificity, and which describes the source of protection?
I can compare innate/adaptive and natural/artificial active/passive immunity.
I can compare innate/adaptive and active/passive, natural/artificial immunity.Syllabus
Syllabus 9477, Extension A(a). Compare innate/adaptive and active/passive, natural/artificial immunity.
About 7 min
Make a guess. You are not marked.
A baby receives antibodies from its mother in breast milk. What kind of immunity is this?
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Natural passive immunity.
The antibodies are ready-made and come from someone else. The baby makes no memory cells, so protection fades.
The key idea
Innate/adaptive describes the response system; active/passive describes whether the recipient makes the protective response or receives antibodies.
From recognition to response
Does the recipient make a response or receive antibodies?
Pathogen antigen stimulates the recipient's own adaptive response. Selected cells can expand and form memory; protection is not instantaneous or guaranteed.
Triangle = antigenic feature; Y = antibody. This active/passive comparison is a different classification from innate/adaptive. Innate barriers and cells can act alongside every route shown.
Explanation
Innate defences respond rapidly using broadly shared pathogen features. Physical barriers, mucus, antimicrobial chemicals, phagocytes, inflammation and complement contribute. They do not depend on first expanding a newly selected antigen-specific lymphocyte clone.
Adaptive immunity uses highly specific B- and T-cell receptors and produces immunological memory. A first response takes time for activation and clonal expansion; a later response to the same antigen can be faster and stronger. Innate and adaptive systems interact rather than operating as isolated alternatives.
Active immunity develops when the person's own adaptive system responds. It may follow natural infection or artificial antigen exposure by vaccination. Memory cells can persist, although duration and completeness of protection vary.
Passive immunity supplies preformed antibodies. Natural examples include maternal antibody transfer, while artificially supplied antibody preparations provide another example. Protection can act quickly but wanes as the transferred antibodies are removed, and the transfer itself does not establish the recipient's antigen-specific memory response.
Step by step
- 1
Choose the classification axis
System type differs from source of antibodies.
- 2
Identify who produces antibodies
Recipient or external source?
- 3
Predict timing and memory
Immediate temporary protection differs from priming a response.
Worked example
Work through the evidence
A newborn receives maternal IgG across the placenta. Classify this and explain the lack of new immune memory from the transfer itself.
One way to explain it
It is naturally acquired passive immunity. Antibodies are transferred from the mother; the transfer does not itself select and expand the newborn's corresponding memory-cell population.
Why this answer works
- Natural/artificial refers to acquisition route.
- Passive/active refers to who mounts the response.
Watch out for this
A student says: "Passive immunity means antibodies do nothing until infection ends." What is wrong with this?
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Transferred antibodies can act immediately; passive refers to their external source.
Check your understanding
A vaccine stimulates the recipient's own memory response. This is...
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artificially acquired active immunity.
Vaccination deliberately stimulates the recipient's adaptive response.
Quick recall
Which distinction describes specificity, and which describes the source of protection?