How do white blood cells protect us from infection?

Sometimes microorganisms are able to make it past the body's external defences (i.e. the skin) the body's immune system must defend the body.

White blood cells are really important in the immune response. They circulate in the blood along with red blood cells and other components.

There are different types of white blood cells - some are able to engulf and digest microorganisms so that they are completely destroyed. This kills microorganisms very quickly and happens they first invade the immune system.

Other white blood cells are able to generate and release special chemicals called antibodies. These are attracted to special markers on the surface of microorganisms called ANTIGENS. Each white blood cell is specific to only one type of antigen. Antibodies are released, they attach to their specific antigen on the surface of microorganisms - microorganisms can then be bunched up into clumps, making it easier for white blood cells to engulf and digest them.

Antibodies take time to generate but once they are, the body is able to recognise specific microorganisms and can react quickly to release antibodies in future attacks - this is called natural immunity.