# Describe how the human immune system responds when a pathogen enters the body for the first time, and explain why a second infection by the same pathogen is dealt with more quickly.

> Eduqas A-Level Biology — 3.3 Microbiology · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. White blood cells detect antigens on the surface of the pathogen
2. Lymphocytes release antibodies that are complementary/specific to the antigen, which bind to and neutralise the pathogen
3. Phagocytes engulf and digest the pathogen using enzymes (phagocytosis)
4. After the first infection, memory cells remain in the body
5. On second infection, memory cells rapidly divide and produce the correct antibodies much more quickly, destroying the pathogen before symptoms develop

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-the-human-immune-system-35fb2fbe) · Published by Druglandscape Ltd.