The Merck Manual states that blood has four main components: plasma, red blood cells, white blood cells and platelets. White blood cells, far less in number in the blood than red blood cells, are part of the immune system. White blood cells as a group are also known as leukocytes. All together the white blood cells act as an army for the body, organizing where to call in troops and when to launch attacks. There are five main types of white blood cells that help defend the body.
Neutrophils
According to ThinkQuest.org, neutrophils make up 55 to 70 percent of the white blood cells found in the body. Neutrophils are the garbage disposals of the body as they circulate the blood stream and eat up foreign particles, debris, bacteria and fungi. Neutrophils always increase in number during an active infection and are also found in the pus of wounds.
Lymphocytes
These cells are the second most common type of white blood cell, making up 20 to 40 percent of the white blood cells, and have three main types according to the Merck Manual. Lymphocytes are composed of T lymphocytes, B lymphocytes and killer cells. The T lymphocytes break down even further but the role of the lymphocytes is to attack infections, viruses and even early stages of cancer. Lymphocytes have a very specific action and can also lump infective cells together, produce antibodies and memory cells. These memory cells help the body fight off a previously recognized infection, like chicken pox.
Monocytes
Monocytes make up 5 to 8 percent of white blood cells and are are the largest in size of all the white blood cells. The monocytes are also a type of macrophage, or big eater. These cells will eat up particles that are too large for the neutrophils or that the lymphocytes have clumped together.
Eosinophils
According to ThinkQuest.org, eosinophils make up 2 to 5 percent of the white blood cells. They are the main reason for allergic response in the bloodstream and are also responsible for attacking parasites. During a parasitic infection, eosinophils will greatly increase in number.
Basophils
Basophils are the least in number, normally making up less than 1 percent of the white blood cells. They will sharply increase during an allergic response and are responsible for the release of histamine. Basophils will also be involved in an immediate immune response with germs or foreign bodies until more white blood cells arrive.
