What are the functions of white blood cells?

The main role of white blood cells is to protect the body against invasion by disease-causing microorganisms (pathogens), such as bacteria or viruses. They do this in 2 main ways: phagocytosis and antibody production. Around 75% of white blood cells are phagocytes, these are the cells which phagocytose ('cell eating'). The process involves ingesting microorganisms, by changing their shape and producing extensions in their cytoplasm, called pseudopodia. These enclose and enclose the microorganism in a vacuole. The phagocyte then secretes enzymes into the vacuole which break down the microorganism. The other type of white blood cell to be aware of are lymphocytes. Their function is to make antibodies. These are soluble proteins, that pass into the plasma, and can recognise the telltale chemical 'markers' called antigens on the surface of pathogens. The antibodies stick to these antigens and destroy the pathogen in several different ways. For example: 1) they can cause the different pathogens to stick together, so phagocytes can ingest them more easily 2) acting as a label on the pathogens so phagocytes recognise them more easily 3) cause the pathogen cells to burst 4) neutralise the toxins produced by the pathogens Finally, some lymphocytes develop into memory cells, which help to make us immune to a disease. These cells stay in the blood for many years, and so if a microorganism re-infects, the memory cell can quickly reproduce and produce antibodies, to deal with the infection much faster.