Infection & ResponseDefinitions

Key Definitions

Part of Adaptive Immunity and Antibodies · GCSE GCSE Biology revision

This definitions covers Key Definitions within Adaptive Immunity and Antibodies for GCSE Biology. Specific immune responses, antibody production, lymphocytes, memory cells It is section 8 of 15 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.

Topic position

Section 8 of 15

Practice

23 questions

Recall

12 flashcards

Key Definitions

Antigen: A foreign molecule (usually a protein on the surface of a pathogen) that triggers an immune response. Each antigen has a unique molecular shape that the immune system recognises.

Antibody: A Y-shaped protein produced by plasma cells (differentiated B lymphocytes) that binds specifically to one antigen. Antibodies tag pathogens for destruction by phagocytes and neutralise toxins.

Antitoxin: An antibody that binds to and neutralises a toxin produced by a pathogen, preventing it from causing harm to the body.

B lymphocyte (B cell): A type of white blood cell that, when activated by a specific antigen, divides to produce plasma cells (which secrete antibodies) and memory B cells.

T lymphocyte (T cell): A type of white blood cell. Helper T cells coordinate the immune response and activate B cells. Killer T cells directly destroy infected or abnormal cells.

Plasma cell: A differentiated B lymphocyte that acts as an antibody factory, secreting thousands of antibody molecules per second specific to one antigen.

Memory cell: A long-lived lymphocyte (B or T cell) produced during a primary immune response that remains in the body and enables a faster, stronger secondary response on re-exposure to the same antigen.

Primary immune response: The slow initial response to first exposure to an antigen. Takes 5–10 days to produce significant antibody levels; produces memory cells.

Secondary immune response: The rapid, strong response to subsequent exposure to the same antigen. Memory cells respond within 1–3 days and produce higher antibody levels; often prevents disease symptoms entirely.

Keep building this topic

Read this section alongside the surrounding pages in Adaptive Immunity and Antibodies. That gives you the full topic sequence instead of a single isolated revision point.

How It Works: Antibodies as a Lock-and-Key System Key Facts About Adaptive Immunity The Body's Elite Forces Understanding Antigens

Practice Questions for Adaptive Immunity and Antibodies

What are antigens?

A. Antibodies produced by white blood cells
B. Unique proteins on the surface of pathogens
C. Toxins produced by bacteria
D. Memory cells that remain after infection

1 markfoundation

Explain how lymphocytes produce antibodies to destroy a specific pathogen.

3 marksstandard

Quick Recall Flashcards

What is an antibody?

A protein produced by lymphocytes (white blood cells) that binds to a specific antigen. Each antibody has a unique shape that fits one antigen only — like a lock and key.

What is an antigen?

A protein on the surface of a pathogen (or cell) that the immune system recognises as foreign. Antigens trigger the body to produce antibodies.

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How It Works: Antibodies as a Lock-and-Key System

Key Facts About Adaptive Immunity