White Blood Cells (Cambridge (CIE) IGCSE Biology): Revision Note

Lymphocytes & phagocytes: Extended

Extended Tier Only

• White blood cells are part of the body’s immune system, defending against infection by pathogens

• There are two main types: phagocytes and lymphocytes

Phagocytes

• Phagocytes carry out phagocytosis by engulfing and digesting pathogens

• Phagocytes have a sensitive cell surface membrane that can detect chemicals produced by pathogens

• Once phagocytes encounter a pathogen, they will engulf it and release digestive enzymes to digest it

• Phagocytes can be easily recognised under the microscope as cells with multi-lobed nucleus and granular cytoplasm

Lymphocytes

• Lymphocytes produce antibodies to destroy pathogens and antitoxins to neutralise toxins released by pathogens

• Lymphocytes can easily be recognised under the microscope as cells with a large round nucleus which takes up nearly the whole cell and clear, non-granular cytoplasm