Warzone: S. aureus bacteria escaping destruction by human white blood cells.
White blood cells are at once the intelligence agents and the crack commandos of the body’s immune system. They’re the special forces that hasten to the scene of an attack whenever germs or infections are entering the body. Their mission: to take out invading pathogens, and generally to defend against infectious diseases and foreign substances – like potentially malevolent bacteria.
Image: Unknown photographer/artist
White knight: Electron microscopic image of a single human Lymphocyte cell.
There are five main types of white blood cells – all constantly on the lookout for signs of disease and armed with various ways in which they can attack – but by far the most prolific are the Neutrophils and the Lymphocytes, which together make up between 87 and 94% of the white blood cells in our body.
Found mainly in the lymphatic system, Lymphocytes step up in increasing numbers in response to viral infections and tumour cells. Lymphocytes detect the foreign substances of germs in the body and produce protective antibodies and cells specifically designed to target and overpower them.
Mid-fight: Neutrophil immune cell engulfing anthrax bacteria.
Big shots in the body’s fight against bacterial infections, Neutrophils circulate in the bloodstream, moving into infected tissue to attack the bacteria. Neutrophils take a more direct, ‘hands-on’ approach than Lymphocytes: after responding to chemicals released by bacteria and dead tissue cells, they rush towards the area of highest concentration, then surround and devour the offending cells, destroying them with powerful enzymes. Called phagocytosis, this vacuum cleaner-like process uses up so much energy that the Neutrophils die soon after, and their activity and death in large numbers forms pus.