White blood cells are the immune systems way of guarding the body against any foreign material, disease causing and otherwise, that enters the body. Any increases in the number of white blood cells in the blood indicate any number of disorders. White blood cells are also known as leukocytes. Blood contains five primary types of white blood cell, each of which has their own unique function.
Neutrophils are the kind that patrol the bloodstream and engulf any foreign organisms. These cells are primarily responsible for defending the body against bacterial or fungal infections. The activity of these cells, and consequent death, are what creates pus around wounds. The cells use lysosomes to digest pathogens, however lysosomes cannot be renewed and so the cells die quickly, after only ingested several pathogens. This type belongs to the phagocyte class of cells. Once neutrophils reach the area of infection they respond to the chemicals that are released by bacteria and dead cells. They then move toward the highest concentration of them and begin to destroy the bacteria with powerful enzymes.
Monocytes, which are also phagocytes, are responsible for patrolling through the bodies different tissues. Despite having a similar role as neutrophils monocytes are usually much longer lived. These cells, once they have left the blood stream are responsible for removing dead cell debris in addition to attacking microorganisms. Monocytes are able to replace their lysomal content and so they have a much longer life than neutrophils.
Basophils are responsible for releasing chemicals that trigger an inflammatory response. These cells release the chemical histamine which results in the inflammation. Eosinophils are similarly responsible for triggering allergic reactions. These cells also deal with parasitic infections. Eosinophils play a huge part in allergies such as hay fever, asthma and hives. This type of cell is also partly responsible for anaphylactic shock. Basophils are the least common type of white blood cell.
The last type of white blood cell is the lymphocyte which is responsible for targeting infective organisms such as viruses. This last type of cell is also capable of locking on to and destroying cancer cells. These cells are more often found in the lymphatic system and increase greatly in number when the body has a viral infection. Lymphocytes are the most common white blood cell in children, and the second most common in adults. There are two major types of lymphocytes that are found in the blood. The two types are B-lymphocytes and T-lymphocytes, each with their own unique functions.