Innate immunity: phagocytes
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Flip to reveal answersWhat are the three key features of the innate immune system?
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Question
What are the three key features of the innate immune system?
Answer
It is **fast**, **non-specific**, and has **no memory**.
Question
Which type of leucocyte carries out the innate response?
Answer
**Phagocytes** — for example **macrophages** and **neutrophils**.
Question
Define a phagocyte.
Answer
A type of white blood cell (leucocyte) that **engulfs and digests pathogens** by phagocytosis.
Question
Define phagocytosis.
Answer
The process in which a phagocyte **engulfs a pathogen, encloses it in a vacuole, and digests it with enzymes**.
Question
List the steps of phagocytosis in order.
Answer
**Recognise** the pathogen → **engulf** it → **enclose** it in a vacuole → **digest** it with enzymes.
Question
What does 'non-specific' mean for the innate system?
Answer
It acts against **any pathogen** in the same way, rather than targeting just one type.
Question
What is a vacuole's role in phagocytosis?
Answer
It is the **membrane-bound 'bubble'** that holds the engulfed pathogen while enzymes break it down.
Question
What destroys the pathogen inside the phagocyte?
Answer
**Enzymes** released into the vacuole, which break the pathogen down.
Question
How does the innate system differ from the adaptive system?
Answer
Innate = **fast, non-specific, no memory** (phagocytes). Adaptive = **slow, specific, has memory** (lymphocytes).
Question
Are lymphocytes (B-cells and T-cells) part of the innate system?
Answer
**No** — they are part of the **adaptive** system. The innate cells are the phagocytes.
Question
Which cell count rises FIRST during an infection, and why?
Answer
The **phagocyte** count rises first, because the innate response is the **fast** one; lymphocytes rise later.
Question
Why can phagocytes respond almost immediately to a new pathogen?
Answer
Because they are **non-specific** — they do not need to 'learn' the pathogen first, so they act straight away.
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Topic 3.7 hub
Defence against infectious disease
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