White blood cell: Difference between revisions

| Name = White blood cell

| Latin=

| Image2 =

| Caption2 =

| Precursor =

| Acronym = WBC

 

 

All white blood cells are produced and derived from [[multipotent]] cells in the [[bone marrow]] known as [[hematopoietic stem cell]]s.<ref name="Monga">{{cite journal | vauthors = Monga I, Kaur K, Dhanda S| title = Revisiting hematopoiesis: applications of the bulk and single-cell transcriptomics dissecting transcriptional heterogeneity in hematopoietic stem cells | journal = Briefings in Functional Genomics | volume = 21 | issue = 3 | pages = 159–176 | date = March 2022 | pmid = 35265979 | doi = 10.1093/bfgp/elac002}}</ref> Leukocytes are found throughout the body, including the [[blood]] and [[lymphatic system]].<ref>{{cite book | vauthors = Maton D, Hopkins J, McLaughlin CW, Johnson S, Warner MQ, LaHart D, Wright JD, Kulkarni DV | title = Human Biology and Health | publisher = Prentice Hall | year = 1997 | location = Englewood Cliffs, New Jersey, US | url = https://archive.org/details/humanbiologyheal00scho | isbn = 0-13-981176-1 }}</ref> All white blood cells have [[cell nucleus|nuclei]], which distinguishes them from the other [[blood cell]]s, the anucleated [[red blood cell]]s (RBCs) and [[platelet]]s. The different white blood cells are usually classified by [[cell division|cell]] lineage ([[myelocyte|myeloid cells]] or [[lymphocyte|lymphoid cells]]). White blood cells are part of the body's immune system. They help the body fight [[infection]] and other diseases. Types of white blood cells are granulocytes (neutrophils, eosinophils, and basophils), and agranulocytes ([[monocyte]]s, and [[lymphocyte]]s (T cells and B cells)).<ref>{{Cite web |date=2011-02-02 |url=https://www.cancer.gov/publications/dictionaries/cancer-terms/def/white-blood-cell |access-date=March 15, 2023 |title=Definition of white blood cell |website=www.cancer.gov |language=en}}</ref> Myeloid cells ([[myelocytes]]) include [[neutrophil granulocyte|neutrophils]], [[eosinophil granulocyte|eosinophils]], [[mast cells]], [[basophil granulocyte|basophils]], and [[monocyte]]s.<ref name="isbn978-0-323-04950-4">{{cite book |vauthors=LaFleur-Brooks M |title=Exploring Medical Language: A Student-Directed Approach |edition=7th |publisher=Mosby Elsevier |location=St. Louis, Missouri, US |year=2008 |page=[https://archive.org/details/exploringmedical00myrn/page/398 398] |isbn=978-0-323-04950-4 |url=https://archive.org/details/exploringmedical00myrn/page/398 }}</ref> Monocytes are further subdivided into [[dendritic cells]] and [[macrophages]]. Monocytes, macrophages, and neutrophils are [[phagocytic]]. Lymphoid cells ([[lymphocytes]]) include [[T cells]] (subdivided into [[helper T cell]]s, [[memory T cell]]s, [[cytotoxic T cell]]s), [[B cells]] (subdivided into [[plasma cells]] and [[memory B cells]]), and [[natural killer cells]]. Historically, white blood cells were classified by their physical characteristics ([[granulocytes]] and [[agranulocytes]]), but this classification system is less frequently used now. Produced in the [[bone marrow]], white blood cells defend the body against [[infection]]s and [[disease]]. An excess of white blood cells is usually due to infection or inflammation. Less commonly, a high white blood cell count could indicate certain blood cancers or bone marrow disorders.

 

==Etymology==

 

 

===Overview===

All white blood cells are nucleated, which distinguishes them from the anucleated red blood cells and platelets. Types of leukocytes can be classified in standard ways. Two pairs of broadest categories classify them either by structure ([[granulocyte]]s or [[agranulocyte]]s) or by cell lineage (myeloid cells or lymphoid cells). These broadest categories can be further divided into the five main types: [[neutrophil]]s, [[eosinophil]]s, [[basophil]]s, [[lymphocyte]]s, and [[monocyte]]s.<ref name="isbn978-0-323-04950-4"/> A good way to remember the relative proportions of WBCs is "Never Let Monkeys Eat Bananas".<ref>{{cite web | url=https://www.uwyo.edu/virtual_edge/lab22/introduction_wright.htm | title=The Virtual Edge }}</ref> These types are distinguished by their physical and functional characteristics. Monocytes and neutrophils are [[phagocytic]]. Further subtypes can be classified.

 

! (illustration)

|-

| [[Image:pBNeutrophil.jpg|60px]] || [[File:Blausen 0676 Neutrophil (crop).png|70x70px]] || 62% || 12–15 ||

* [[Bacteria]]

| [[Multilobed]] || Fine, faintly pink (H&E stain) || 6 hours – few days<br>(days in [[spleen]] and other tissue)

|-

* Larger [[parasite]]s

* Modulate [[allergy|allergic]] [[inflammation|inflammatory]] responses

| [[Bi-lobed]] || Full of pink-orange (H&E stain)|| 8–12 days (circulate for 4–5 hours)

|-

* Release [[histamine]] for [[inflammation|inflammatory]] responses

|[[Bi-lobed]] or [[tri-lobed]] || Large blue || A few hours to a few days

* [[B cell]]s: releases antibodies and assists activation of T cells

* [[T cell]]s:

** [[CD8]]+ [[cytotoxic T cell]]s: [[virus (biology)|virus]]-infected and [[tumor]] cells.

** [[Gamma delta T cell]]s: bridge between [[Innate immune system|innate]] and [[Adaptive immune system|adaptive]] immune responses; phagocytosis

| Deeply staining, eccentric || NK-cells and cytotoxic (CD8+) T-cells || Years for memory cells, weeks for all else.

|-

{{Main|Neutrophil}}

[[Image:Neutrophil with anthrax copy.jpg|210px|right|thumb|Neutrophil engulfing [[Bacillus anthracis|anthrax bacteria]]]]

 

===Eosinophil===

{{Main|Eosinophil}}

 

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 parasitic infections. They secrete chemicals that destroy large parasites, such as hookworms and tapeworms, that are too big for any one white blood cell to phagocytize. In general, their nuclei are bi-lobed. The lobes are connected by a thin strand.<ref name=Saladin /> The cytoplasm is full of granules that assume a characteristic pink-orange color with [[eosin]] staining.

 

===Basophil===

{{Main|Basophil}}

Basophils are chiefly responsible for [[allergy|allergic]] and [[antigen]] response by releasing the chemical [[histamine]] causing the [[vasodilation|dilation of blood vessels]]. Because they are the rarest of the white blood cells (less than 0.5% of the total count) and share physicochemical properties with other blood cells, they are difficult to study.<ref>{{cite journal | vauthors = Falcone FH, Haas H, Gibbs BF | title = The human basophil: a new appreciation of its role in immune responses | journal = Blood | volume = 96 | issue = 13 | pages = 4028–38 | date = December 2000 | doi = 10.1182/blood.V96.13.4028 | pmid = 11110670 | url = http://www.bloodjournal.org/content/96/13/4028 }}</ref> They can be recognized by several coarse, dark violet granules, giving them a blue hue. The nucleus is bi- or tri-lobed, but it is hard to see because of the number of coarse granules that hide it.

 

===Lymphocyte===

{{Main|Lymphocyte}}

Lymphocytes are much more common in the lymphatic system than in blood. Lymphocytes are distinguished by having a deeply staining nucleus that may be eccentric in location, and a relatively small amount of cytoplasm. Lymphocytes include:

* [[B cell]]s make [[antibody|antibodies]] that can bind to [[pathogens]], block pathogen invasion, activate the [[complement system]], and enhance pathogen destruction.

* [[T cell]]s:

** [[CD8]]+ [[cytotoxic T cells]]: T cells displaying co-receptor [[CD8]] are known as CD8+ T cells. These cells bind antigens presented on [[MHC I]] complex of virus-infected or tumour cells and kill them. Nearly all nucleated cells display MHC I.

 

===Monocyte===

{{Main|Monocyte}}

Monocytes, the largest type of white blood cell, share the "vacuum cleaner" ([[phagocytosis]]) function of neutrophils, but are much longer lived as they have an extra role: they present pieces of [[pathogen]]s to T cells so that the pathogens may be recognized again and killed. This causes an antibody response to be mounted. Monocytes eventually leave the bloodstream and become tissue [[macrophage]]s, which remove dead cell debris as well as attack microorganisms. Neither dead cell debris nor attacking microorganisms can be dealt with effectively by the neutrophils. Unlike neutrophils, monocytes are able to replace their [[lysosome|lysosomal]] contents and are thought to have a much longer active life. They have the kidney-shaped nucleus and are typically not granulated. They also possess abundant cytoplasm.

 

==Fixed leucocytes==

[[Image:Hematopoiesis simple.svg|thumb|420px|HSC=[[Hematopoietic stem cell]], Progenitor=[[Progenitor cell]], L-blast=[[Lymphoblast]], [[Lymphocyte]], Mo-blast=[[Monoblast]], [[Monocyte]], [[Myeloblast]], Pro-M=[[Promyelocyte]], [[Myelocyte]], Meta-M=[[Metamyelocyte]], [[Neutrophil]], [[Eosinophil]], [[Basophil]], Pro-E=[[Proerythroblast]], Baso-E=[[Basophilic erythroblast]], poly-E=[[Polychromatic erythroblast]], Ortho-E=[[Orthochromatic erythroblast]], [[Erythrocyte]], [[Promegakaryocyte]], [[Megakaryocyte]], [[Platelet]]]]

Some leucocytes migrate into the tissues of the body to take up a permanent residence at that location rather than remaining in the blood. Often these cells have specific names depending upon which tissue they settle in, such as fixed macrophages in the liver, which become known as [[Kupffer cell]]s. These cells still serve a role in the immune system.

* [[Histiocyte]]s

===Leukopenias===

{{Main|Leukopenia}}

A range of disorders can cause decreases in white blood cells. This type of white blood cell decreased is usually the neutrophil. In this case the decrease may be called [[neutropenia]] or granulocytopenia. Less commonly, a decrease in lymphocytes (called [[lymphocytopenia]] or lymphopenia) may be seen.<ref name="Al2010" />

 

====Neutropenia====

{{Main|Neutropenia}}

[[Neutropenia]] can be [[acquired characteristic|acquired]] or [[congenital disorder|intrinsic]].<ref>{{cite book | veditors = McPherson RA, Pincus MR, Abraham NZ |title=Henry's clinical diagnosis and management by laboratory methods|year=2011|publisher=Elsevier/Saunders|location=Philadelphia, PA|isbn=978-1437709742|edition=22nd|display-editors=etal}}</ref> A decrease in levels of neutrophils on lab tests is due to either decreased production of neutrophils or increased removal from the blood.<ref name="Al2010" /> The following list of causes is not complete.

* Radiation

* Any major infection

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 [[drug overdose|medication overdose]] or toxicity.

Treatment is also aimed at the underlying cause of the neutropenia.<ref name="Schafer_a" /> One severe consequence of neutropenia is that it can increase the risk of infection.<ref name="Williamshematology2010" />

====Lymphocytopenia====

{{Main|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.<ref name="Williamshematology2010" /> This is not a complete list.

* Radiation

* Major surgery

Like neutropenia, symptoms and treatment of lymphocytopenia are directed at the underlying cause of the change in cell counts.

 

===Proliferative disorders===

{{Main|Leukocytosis}}

An increase in the number of white blood cells in [[circulatory system|circulation]] is called [[leukocytosis]].<ref name="Al2010" /> This increase is most commonly caused by [[inflammation]].<ref name="Al2010" /> 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.<ref name="Al2010" /> Leukocytosis may affect one or more cell lines and can be neutrophilic, eosinophilic, basophilic, monocytosis, or lymphocytosis.

 

====Neutrophilia====

{{Main|Neutrophilia}}

Neutrophilia is an increase in the absolute neutrophil count in the [[systemic circulation|peripheral circulation]]. Normal blood values vary by age.<ref name="Williamshematology2010" /> 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.<ref name="Schafer_a"/>

 

Secondary causes<ref name="Schafer_a" />

* [[Infection]]

* [[Cigarette smoking]] – occurs in 25–50% of chronic smokers and can last up to 5 years after quitting

* Stress – exercise, surgery, general stress

==Counting and reference ranges==

{{Main|White blood cell differential}}

The [[complete blood count|complete blood cell count]] is a [[blood panel]] that includes the overall white blood cell count and [[white blood cell differential|differential]] count, a count of each type of white blood cell. [[Reference ranges for blood tests]] specify the typical counts in healthy people.