These cells store histamine, are located in the blood, store heparin (anti-coagulant preventing rapid blood clotting), are the least numerous of the granulocytes and account for less than 1 percent of all white blood cells occurring in the human body.

A principal type of white blood cell that completes maturation in the thymus. This cells identify specific foreign antigenic peptides presented to it in the body by other cells, which it then kills.

A type of cell that provides help to other cells in the immune response by recognizing foreign antigens and secreting substances called cytokines that activate killer T cells and B cells.

A special type of cell that is a key regulator of the immune system, acting as a professional antigen-presenting cell (APC) capable of activating naive T cells and stimulating the growth and differentiation of B cells.

A normal type of white blood cell that has coarse granules within its cytoplasm. These are produced in the bone marrow and migrate to tissues throughout the body. When a foreign substance enters the body, other types of white blood cells (lymphcytes and neutrophils) release substances to attract these cells and then release toxic substances to kill the invader.

A type of white blood cell that ingests foreign material. These cells are key players in the immune response to foreign invaders of the body, such as infectious microorganisms. They are normally found in the liver, spleen, and connective tissues of the body.

Derived from the myeloid stem cell and a part of the immune system that contains many granules rich in histamine and heparin. Although best known for their role in allergy and anaphylaxis, these cells play an important protective role as well, being intimately involved in wound healing and defense against pathogens. They are located in connective tissue.

A type of white blood cell. They are the largest of all leukocytes. They are amoeboid in shape, having clear cytoplasm. They have bean-shaped nuclei that are unilobar, which makes them one of the types of mononuclear leukocytes (agranulocytes). They constitute 2% to 10% of all leukocytes in the human body. They play multiple roles in immune function. Such roles include: (1) replenishing resident macrophages under normal states, and (2) in response to inflammation signals. These cells can move quickly (approx. 8–12 hours) to sites of infection in the tissues and divide/differentiate into macrophages and dendritic cells to elicit an immune response. Half of them are stored in the spleen.

These cells contain a nucleus divided into 2–5 lobes. They are a type of phagocyte and are normally found in the bloodstream. They migrate through the blood vessels, then through interstitial tissue, following chemical signals such as Interleukin-8 (IL-8) in a process called chemotaxis. They are the predominant cells in pus, accounting for its whitish/yellowish appearance. They are recruited to the site of injury within minutes following trauma, and are the hallmark of acute inflammation.

White blood cells that secrete large volumes of antibodies. They are transported by the blood plasma and the lymphatic system. They originate in the bone marrow; however, these cells leave the bone marrow as B cells, before terminal differentiation in the lymph nodes occurs, where they become _________?