White blood cell

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This article is about the cells of the immune system also known as white blood cells. For the album by the band The White Stripes, see White Blood Cells (album).
White blood cell (WBC)
SEM blood cells.jpg
Latin leucocytes
TH H2.
FMA 62852
Anatomical terminology


Five different and diverse types of leukocytes exist.[2] These types are distinguished by their physical and functional characteristics. Monocytes and neutrophils are phagocytic.

The number of leukocytes in the blood is often an indicator of disease, and thus the WBC count is an important subset of the complete blood count. The normal white cell count is usually between 4 and 11 × 109/L. In the US this is usually expressed as 4,000–11,000 white blood cells per microliter of blood.[3] They make up approximately 1% of the total blood volume in a healthy adult.[4] An increase in the number of leukocytes over the upper limits is called leukocytosis, and a decrease below the lower limit is called leukopenia.




3D rendering of various types of white blood cells

All white blood cells are nucleated but are otherwise distinct in form and function. White cells are best classified into two major line-ages: the myeloid leukocytes and the lymphocytes.[5]

The white cells of the myeloid lineage include neutrophils, monocytes, eosinophils and basophils.

Lymphocytes include M cells, B cells and natural killer cells.


Type Microscopic appearance Diagram Approx. %
in adults
See also:
Blood values
Diameter (μm)[6] Main targets[4] Nucleus[4] Granules[4] Lifetime[6]
(days in spleen and other tissue)
Monocyte Monocyte.jpg Monocyte.png 5.3% 15–30[7] Monocytes migrate from the bloodstream to other tissues and differentiate into tissue resident macrophages, Kupffer cells in the liver. Kidney shaped None Hours to days


Neutrophil engulfing anthrax bacteria

Neutrophils are the most abundant white blood cell, constituting 60-70% of the circulating leukocytes.[4] They defend against bacterial or fungal infection. They are usually first responders to microbial infection; their activity and death in large numbers forms pus. They are commonly referred to as polymorphonuclear (PMN) leukocytes, although, in the technical sense, PMN refers to all granulocytes. They have a multi-lobed nucleus, which consists of three to five lobes connected by slender strands.[8] This gives the neutrophils the appearance of having multiple nuclei, hence the name polymorphonuclear leukocyte. The cytoplasm may look transparent because of fine granules that are pale lilac when stained. Neutrophils are active in phagocytosing bacteria and are present in large amount in the pus of wounds. These cells are not able to renew their lysosomes (used in digesting microbes) and die after having phagocytosed a few pathogens.[9] Neutrophils are the most common cell type seen in the early stages of acute inflammation. The life span of a circulating human neutrophil is about 5.4 days.[10]



They primarily deal with parasitic infections. Eosinophils are also the predominant inflammatory cells in allergic reactions. The most important causes of eosinophilia include allergies such as asthma, hay fever, and hives; and also parasitic infections. They secrete chemicals that destroy these large parasites, such as hook worms and tapeworms, that are too big for any one WBC to phagocytize. In general, their nucleus is bi-lobed. The lobes are connected by a thin strand.[8] The cytoplasm is full of granules that assume a characteristic pink-orange color with eosin staining.


Main article: Basophil granulocyte




Main article: Lymphocyte



Main article: Monocyte



Fixed leukocytes[edit]





Main article: Leukopenia



Main article: Neutropenia

Neutropenia can be acquired or intrinsic.[14] A decrease in levels of neutrophils on lab tests is due to either decreased production of neutrophils or increased removal from the blood.[12] The following list of causes is not complete.

Symptoms of neutropenia are associated with the underlying cause of the decrease in neutrophils. For example, the most common cause of acquired neutropenia is drug-induced, so an individual may have symptoms of medication overdose or toxicity. Treatment is also aimed at the underlying cause of the neutropenia.[15] One severe consequence of neutropenia is that it can increase the risk of infection.[13]


Main article: Lymphocytopenia

Defined as total lymphocyte count below 1.0x109/L, the cells most commonly affected are CD4+ T cells. Like neutropenia, lymphocytopenia may be acquired or intrinsic and there are many causes.[13] This is not a complete list.


Proliferative disorders[edit]

Main article: Leukocytosis

An increase in the number of white blood cells in circulation is called leukocytosis.[12] This increase is most commonly caused by inflammation.[12] There are four major causes: increase of production in bone marrow, increased release from storage in bone marrow, decreased attachment to veins and arteries, decreased uptake by tissues.[12] Leukocytosis may affect one or more cell lines and can be neutrophilic, eosinophilic, basophilic, monocytosis, or lymphocytosis.


Main article: Neutrophilia

Neutrophilia is an increase in the absolute neutrophil count in the peripheral circulation. Normal blood values vary by age.[13] Neutrophilia can be caused by a direct problem with blood cells (primary disease). It can also occur as a consequence of an underlying disease (secondary). Most cases of neutrophilia are secondary to inflammation.[15]

Primary causes[15]

Secondary causes[15]


Main article: Eosinophilia

A normal eosinophil count is considered to be less than 0.65×109/L.[13] Eosinophil counts are higher in newborns and vary with age, time (lower in the morning and higher at night), exercise, environment, and exposure to allergens.[13] Eosinophilia is never a normal lab finding. Efforts should always be made to discover the underlying cause, though the cause may not always be found.[13]

Counting and reference ranges[edit]


See also[edit]


  5. ^ Orkin, SH; Zon, LI (Feb 22, 2008). "SnapShot: hematopoiesis.". Cell 132 (4): 712. doi:10.1016/j.cell.2008.02.013. PMID 18295585. 
  8. ^ a b c d Saladin, Kenneth (2012). Anatomy and Physiology: the Unit of Form and Function (6 ed.). New York: McGraw Hill. ISBN 978-0-07-337825-1. 
  11. ^ Falcone, Franco; Haas, Helmut; Gibbs, Bernard (15 December 2000). "The human basophil: a new appreciation of its role in immune responses.". Blood 96 (13): 4028–38. PMID 11110670. 
  12. ^ a b c d e f Vinay Kumar; et al. (2010). Robbins and Cotran pathologic basis of disease. (8th ed.). Philadelphia, PA: Saunders/Elsevier. ISBN 1416031219. 
  13. ^ a b c d e f g Kenneth Kaushansky et al., eds. (2010). Williams hematology (8th ed.). New York: McGraw-Hill Medical. ISBN 0071621512. 
  14. ^ Richard A. McPherson, Matthew R. Pincus, Naif Z. Abraham Jr.; et al. (eds.). Henry's clinical diagnosis and management by laboratory methods (22nd ed.). Philadelphia, PA: Elsevier/Saunders. ISBN 1437709745. 
  16. ^ McBride, JA; Dacie, JV; Shapley, R (Feb 1968). "The effect of splenectomy on the leucocyte count.". British journal of haematology 14 (2): 225–31. doi:10.1111/j.1365-2141.1968.tb01489.x. PMID 5635603. 

External links[edit]