Removing pathogens
The bone marrow continually produces phagocytes, which are white blood cells involved in defence against infection. They remove pathogens by taking them into the cell and breaking them down. This overall process is called phagocytosis.
Phagocytosis is part of the non-specific immune response. Two important phagocyte types are neutrophils and macrophages.
Neutrophils
Neutrophils act as phagocytes, taking pathogens into the cell so that they can be destroyed.
Macrophages
Macrophages carry out phagocytosis and can also display antigens obtained from a digested pathogen.
Finding and attaching to a pathogen
- Chemotaxis: substances released from pathogens or damaged body cells form chemical signals that draw phagocytes towards the site.
- Recognition: membrane receptors on the phagocyte detect non-self antigens carried by the pathogen.
- Attachment: binding occurs between the phagocyte receptors and antigens on the pathogen surface.
Exam Tip: Keep the early stages distinct in a sequence answer. Chemotaxis attracts the phagocyte towards the affected area; receptor-antigen binding then allows recognition and attachment.