White blood cell

From Wikipedia, the free encyclopedia

(Redirected from Immune cell)

"White Blood Cells" redirects here. For the White Stripes album, see White Blood Cells (album).

To meet Wikipedia's quality standards, this article may require cleanup.
Please discuss this issue on the talk page, and/or replace this tag with a more specific message. Editing help is available.
This article has been tagged since September 2006.

White blood cells or leucocytes are cells which form a component of the blood. They are produced in the bone marrow and help to defend the body against infectious disease and foreign materials as part of the immune system.

Image:SEM blood cells.jpg

There are normally between 4x10⁹ and 11x10⁹ white blood cells in a litre of healthy adult blood — about 7,000 to 25,000 white blood cells per drop. In conditions such as leukaemia this may rise to as many as 50,000 white blood cells in a single drop of blood. As well as in the blood, white cells are also found in large numbers in the lymphatic system, the spleen, and in other body tissues.

1 Nomenclature
2 Types
3 Other tissue cells
4 Additional images
5 See also
6 External links

[edit] Nomenclature

The name "white cells" derives from the fact that after centrifugation of a blood sample, the white cells are found in the Buffy coat, a thin layer of nucleated cells between the sedimented red blood cells and the blood plasma, which is white in color (or sometimes green, if there are large amounts of neutrophils in the sample, which are high in green myeloperoxidase).A drop of blood can contain anywhere from 7000 to 25000 white blood cells.

[edit] Types

There are many different types of white blood cells. One primary technique to classify them is to look for the presence of granules, which produces the categories "granulocytes" and "agranulocytes".

Granulocytes: As Granular Leucocytes and polymorphonuclear leucocytes (informally, "PMNS" or "Polys"), Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. These granules are related to lysosomes found in some regular cells and primarily act in the digestion of engulfed invaders. There are three types of granulocytes: neutrophils, basophils, and eosinophils (named according to their staining properties).

Agranulocytes: Agranulocytes are a category of white blood cells which are characterized by the absence of granules in their cytoplasm. There are two types of agranulocytes: lymphocytes and monocytes.

These categories can be further broken down as follows:

Type	Image	Diagram	Approx. % in humans	Description
Neutrophil	Image:PBNeutrophil.jpg	Image:Neutrophil.png	65%	Neutrophils deal with defense against bacterial infection and other very small inflammatory processes and are usually first responders to bacterial infection; their activity and death in large numbers forms pus.
Eosinophil		Image:Eosinophil2.png	4%	Eosinophils primarily deal with parasitic infections and an increase in them may indicate such.
Basophil	Image:PBBasophil.jpg	Image:Basophil.png	<1%	Basophils are chiefly responsible for allergic and antigen response by releasing the chemical histamine causing inflammation.
Lymphocyte	Image:Lymphocyte2.jpg	Image:Lymphocyte.png	25%	Lymphocytes are much more common in the lymphatic system. The blood has three types of lymphocytes: B cells: B cells make antibodies that bind to pathogens to enable their destruction. (B cells not only make antibodies that bind to pathogens, but after an attack, some B cells will retain the ability to produce an antibody to serve as a 'memory' system.) T cells: CD4+ (helper) T cells co-ordinate the immune response (they are what becomes defective in an HIV infection) and are important for defence against intracellular bacteria. CD8+ (cytotoxic) T cells are able to kill virus-infected cells. Natural killer cells: Natural killer (NK) cells are able to kill cells of the body which are not displaying a signal not to kill them, as they have been infected by a virus or have become cancerous.
Monocyte	Image:PBMonozyt.jpg	Image:Monocyte.png	6%	Monocytes share the "vacuum cleaner" (phagocytosis) function of neutrophils, but are much longer lived as they have an additional role: they present pieces of pathogens to T cells so that the pathogens may be recognised again and killed, or so that an antibody response may be mounted.
Macrophage	Image:Macrophage.jpg	Image:Macrophage.png	(see above)	Monocytes are also known as macrophages after they migrate from the bloodstream and enter tissue.

[edit] Other tissue cells

Histiocytes, found in the lymphatic system and other body tissues, but not normally in blood:
- Macrophage
- Dendritic cells
Mast cells
Allergies can also change your white blood cell count.

[edit] Additional images

Blood cell lineage

[edit] See also

[edit] External links

Dorlands/Elsevier l_07/12485996
Dictionary at eMedicine leukocyte
MeSH Leukocytes
Animation of leucocyte adhesion Animation with some great images of actin and microtubule assembly and dynamics.

v • d • e</span> Blood - Blood plasma
Pluripotential hemopoietic stem cells \| Red blood cells (Reticulocyte, Normoblast) \| White blood cells
Lymphoid
T cells (Cytotoxic, Helper, Regulatory T cells, Natural Killer T cells) \| B cells (Plasma cells & Memory B cells) \| Natural killer cells
Myeloid
Granulocytes (Neutrophil, Eosinophil, Basophil) \| Mast cell precursors \| Monocytes (Histiocyte, Macrophages, Dendritic cells, Langerhans cells, Microglia, Kupffer cells, Osteoclasts) \| Megakaryoblast \| Megakaryocyte \| Platelets

v • d • e</span> Immune system
Adaptive immune system \| Innate immune system \| Humoral immune system \| Cellular immune system \| Immunological tolerance \| Lymphatic system \| White blood cells \| Antibodies \| Antigen (MHC) \| Complement system \| Inflammation