# Explain how antibodies contribute to the destruction of pathogens in the body.

> IB DP Biology Standard Level (2023 syllabus) — C3.2 Defence against disease · Explain · 4 marks

## Mark scheme (4 marks)

1. Antibodies are proteins produced by plasma cells (effector B cells) that are specific to a particular antigen.
2. Antibodies bind to antigens on the surface of pathogens, forming antigen–antibody complexes.
3. Antibodies can agglutinate (clump) pathogens together, making them easier for phagocytes to engulf.
4. Antibodies can neutralise pathogens or their toxins by blocking active/binding sites, preventing them from entering host cells or causing damage.

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