# Innate immunity

The body's fast, general defences present from birth: skin and mucus barriers, inflammation, and cells such as phagocytes that engulf germs. It reacts the same way each time and has no memory.

Biology (university) · Part 09: Animal physiology · Card 9 of 9 · Last updated 2026-10-19

## Analogy

The locks and guards at the gate, the same for every visitor.

## In practice

A cut gets red and warm as blood flow and white cells increase at the site.

## Practice

### Flashcards

- **Which immunity has no memory?** Innate immunity.

### Interview questions

**Compare innate and adaptive immunity and explain how vaccines work.**

- Innate is fast and general, no memory
- Adaptive is specific, makes memory cells
- Vaccine presents antigen safely
- Second exposure gives faster response

## Questions people ask

### What do phagocytes do?

Phagocytes such as macrophages and neutrophils are white blood cells that engulf germs and digest them. They recognise common features of microbes. They also release chemical signals that trigger inflammation and alert the adaptive immune system. They are among the first cells to arrive at an infection.

### Why does inflammation cause swelling, heat and redness?

Damaged tissue releases chemicals that widen nearby blood vessels and make them leaky. More blood brings heat and redness. Fluid and white cells leak into the tissue, causing swelling. It looks unpleasant, but it helps bring defenders and repair materials to the site.

## Related concepts

- [Adaptive immunity](https://studyvisually.com/learn/science/biology-university/biology-university-part-9/biology-university-part-9-concept-8)

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