White blood cells (scientific name leukocytes), also called immune cells or immunocytes, are

cells Cell most often refers to: * Cell (biology), the functional basic unit of life * Cellphone, a phone connected to a cellular network * Clandestine cell, a penetration-resistant form of a secret or outlawed organization * Electrochemical cell, a d ...

of the

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

that are involved in protecting the body against both

infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

and foreign entities. White blood cells are generally larger than

red blood cells Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

. They include three main subtypes:

granulocyte Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that i ...

lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), an ...

s and

monocyte Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and monocyte-derived dendritic cells. As a part of the vertebrate innate immune system monocytes also ...

s. All white blood cells are produced and derived from

multipotent Cell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency. Potency is also described as the gene activation potential within a cell, which like a continuum ...

cells in the

bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...

known as

hematopoietic stem cell Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the ...

s. Leukocytes are found throughout the body, including the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...

and

lymphatic system The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphoid organs, lympha ...

. All white blood cells have nuclei, which distinguishes them from the other

blood cell A blood cell (also called a hematopoietic cell, hemocyte, or hematocyte) is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), ...

s, the anucleated

red blood cell Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

s (RBCs) and

platelet Platelets or thrombocytes () are a part of blood whose function (along with the coagulation#Coagulation factors, coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a thrombus, blood clot. Platelets have no ...

s. The different white blood cells are usually classified by

cell Cell most often refers to: * Cell (biology), the functional basic unit of life * Cellphone, a phone connected to a cellular network * Clandestine cell, a penetration-resistant form of a secret or outlawed organization * Electrochemical cell, a de ...

lineage (

myeloid cells A myelocyte is a young cell of the granulocytic series, occurring normally in bone marrow (can be found in circulating blood when caused by certain diseases). Structure When stained with the usual dyes, the cytoplasm is distinctly basophilic ...

lymphoid cells A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), and i ...

). White blood cells are part of the body's immune system. They help the body fight

infection An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

and other diseases. Types of white blood cells are granulocytes (neutrophils, eosinophils, and basophils), and agranulocytes (

s, and

s (T cells and B cells)). Myeloid cells (

myelocytes A myelocyte is a young cell (biology), cell of the Granulocyte, granulocytic series, occurring normally in bone marrow (can be found in circulating blood when caused by certain diseases). Structure When stained with the usual dyes, the cytopl ...

) include

neutrophils Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in different ...

eosinophils Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along wi ...

mast cells A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a ...

basophils Basophils are a type of white blood cell. Basophils are the least common type of granulocyte, representing about 0.5% to 1% of circulating white blood cells. They are the largest type of granulocyte. They are responsible for inflammatory reactio ...

, and

s. Monocytes are further subdivided into

dendritic cells A dendritic cell (DC) is an antigen-presenting cell (also known as an ''accessory cell'') of the mammalian immune system. A DC's main function is to process antigen material and present it on the cell surface to the T cells of the immune system ...

and

macrophages Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...

. Monocytes, macrophages, and neutrophils are

phagocytic Phagocytosis () is the process by which a cell (biology), cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs ph ...

. Lymphoid cells (

lymphocytes A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), and ...

) include

T cells T cells (also known as T lymphocytes) are an important part of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their ce ...

(subdivided into

helper T cell The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considere ...

memory T cell Memory T cells are a subset of T lymphocytes that might have some of the same functions as memory B cells. Their lineage is unclear. Function Antigen-specific memory T cells specific to viruses or other microbial molecules can be found in both ...

cytotoxic T cell A cytotoxic T cell (also known as TC, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8+ T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular ...

s),

B cells B cells, also known as B lymphocytes, are a type of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or inserted into the plasm ...

(subdivided into

plasma cells Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B cells and secrete large quantities of proteins called antibodies in response to being presented specific substances c ...

and

memory B cells In immunology, a memory B cell (MBC) is a type of B lymphocyte that forms part of the adaptive immune system. These cells develop within germinal center Germinal centers or germinal centres (GCs) are transiently formed structures within B ...

), and

natural killer cells Natural killer cells, also known as NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system. They are a kind of large granular lymphocytes (LGL), and belong to the rapidly expanding family of known innate lymphoid cells ...

. Historically, white blood cells were classified by their physical characteristics (

granulocytes Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that ...

and

agranulocytes In immunology, agranulocytes (also known as nongranulocytes or mononuclear leukocytes) are one of the two types of leukocytes (white blood cells), the other type being granulocytes. Agranular cells are noted by the absence of granules in their ...

), but this classification system is less frequently used now. Produced in the

, white blood cells defend the body against

s and

disease A disease is a particular abnormal condition that adversely affects the structure or function (biology), function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical condi ...

. 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. The number of leukocytes in the blood is often an indicator of

, and thus the ''white blood cell count'' is an important subset of the

complete blood count A complete blood count (CBC), also known as a full blood count (FBC) or full haemogram (FHG), is a set of medical laboratory tests that provide cytometry, information about the cells in a person's blood. The CBC indicates the counts of white blo ...

. The normal white cell count is usually between 4 billion/L and 11 billion/L. In the US, this is usually expressed as 4,000 to 11,000 white blood cells per microliter of blood. White blood cells make up approximately 1% of the total blood volume in a healthy adult, making them substantially less numerous than the red blood cells at 40% to 45%. However, this 1% of the blood makes a huge difference to health because

immunity Immunity may refer to: Medicine * Immunity (medical), resistance of an organism to infection or disease * ''Immunity'' (journal), a scientific journal published by Cell Press Biology * Immune system Engineering * Radiofrequence immunity ...

depends on it. An increase in the number of leukocytes over the upper limits is called

leukocytosis Leukocytosis is a condition in which the white cell (leukocyte) count is above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, but may also occur following certain parasit ...

. It is normal when it is part of healthy immune responses, which happen frequently. It is occasionally abnormal when it is

neoplastic A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an " autoimmune disease" ...

in origin. A decrease below the lower limit is called

leukopenia Leukopenia () is a decrease in the number of white blood cells (leukocytes). It places individuals at increased risk of infection as white blood cells are the body's primary defense against infections. Signs and symptoms Symptoms may include: * s ...

, which indicates a weakened immune system.

Etymology

The name "white blood cell" derives from the physical appearance of a blood sample after

centrifugation Centrifugation is a mechanical process which involves the use of the centrifugal force to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed. The denser components of the mixture migrate ...

. White cells are found in the ''

buffy coat The buffy coat is the fraction of an anticoagulated blood sample that contains most of the leukocytes and thrombocytes following centrifugation. Description After centrifugation, one can distinguish a layer of clear fluid (the plasma), a laye ...

'', a thin, typically white layer of nucleated cells between the sedimented

s and the

blood plasma Blood plasma is a light Amber (color), amber-colored liquid component of blood in which blood cells are absent, but which contains Blood protein, proteins and other constituents of whole blood in Suspension (chemistry), suspension. It makes up ...

. The scientific term ''leukocyte'' directly reflects its description. It is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

roots ''

leuk Leuk () is a municipality in the district of Leuk in the canton of Valais in Switzerland. On 1 January 2013, the former municipality of Erschmatt merged into the municipality of Leuk.cyt-'' meaning "cell". The

may sometimes be green if there are large amounts of

neutrophil Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in differe ...

s in the sample, due to the heme-containing enzyme myeloperoxidase that they produce.

Types

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 (

s or agranulocytes) or by cell lineage (myeloid cells or lymphoid cells). These broadest categories can be further divided into the five main types:

s, eosinophils, basophils,

s, and

s. A good way to remember the relative proportions of WBCs is "Never Let Monkeys Eat Bananas". These types are distinguished by their physical and functional characteristics. Monocytes and neutrophils are

. Further subtypes can be classified. Granulocytes are distinguished from agranulocytes by their nucleus shape (lobed versus round, that is, polymorphonuclear versus mononuclear) and by their cytoplasm granule (cell biology), granules (present or absent, or more precisely, visible on light microscopy or not thus visible). The other dichotomy is by lineage: Myeloid cells (neutrophils, monocytes, eosinophils and basophils) are distinguished from lymphoid cells (lymphocytes) by haematopoiesis, hematopoietic lineage (cellular differentiation lineage). Lymphocytes can be further classified as T cells, B cells, and natural killer cells.

Neutrophil

Neutrophils are the most abundant white blood cell, constituting 60–70% of the circulating leukocytes. They defend against bacterial or fungal infection. They are usually first responders to microbial infection; their activity and death in large numbers form 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. 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. Neutrophils are the most common cell type seen in the early stages of acute inflammation. The average lifespan of inactivated human neutrophils in the circulation has been reported by different approaches to be between 5 and 135 hours.

Eosinophil

Eosinophils compose about 2–4% of white blood cells in circulating blood. This count fluctuates throughout the day, seasonally, and during menstruation. It rises in response to allergies, parasitic infections, collagen diseases, and disease of the spleen and central nervous system. They are rare in the blood, but numerous in the mucous membranes of the respiratory, digestive, and lower urinary tracts. 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. The cytoplasm is full of granules that assume a characteristic pink-orange color with eosin staining.

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. 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. They secrete two chemicals that aid in the body's defenses: histamine and heparin. Histamine is responsible for widening blood vessels and increasing the flow of blood to injured tissue. It also makes blood vessels more permeable so neutrophils and clotting proteins can get into connective tissue more easily. Heparin is an anticoagulant that inhibits blood clotting and promotes the movement of white blood cells into an area. Basophils can also release chemical signals that attract eosinophils and neutrophils to an infection site.

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 cells make antibody, antibodies that can bind to pathogens, block pathogen invasion, activate the complement system, and enhance pathogen destruction. * T cells: ** CD4+ T helper cells: T cells displaying co-receptor CD4 are known as CD4+ T cells. These cells have T-cell receptors and CD4 molecules that, in combination, bind antigens, antigenic peptides presented on MHC class II, major histocompatibility complex (MHC) class II molecules on antigen-presenting cells. Helper T cells make cytokines and perform other functions that help coordinate the immune response. In HIV infection, these T cells are the main index to identify the individual's immune system integrity. ** 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. ** γδ T cells possess an alternative T cell receptor (different from the αβ TCR found on conventional CD4+ and CD8+ T cells). Found in tissue more commonly than in blood, γδ T cells share characteristics of helper T cells, cytotoxic T cells, and natural killer cells. * Natural killer cells are able to kill cells of the body that do not display MHC class I molecules, or display stress markers such as MHC class I polypeptide–related sequence A (MIC-A). Decreased expression of MHC class I and up-regulation of MIC-A can happen when cells are infected by a virus or become cancerous.

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 pathogens 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 macrophages, 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

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 cells. These cells still serve a role in the immune system. * Histiocytes * Dendritic cells (Although these will often migrate to local lymph nodes upon ingesting antigens) * Mast cells * Microglia

Disorders

The two commonly used categories of white blood cell disorders divide them wikt:quantitative#Adjective, quantitatively into those causing excessive numbers (cell growth, proliferative disorders) and those causing insufficient numbers (

s). Leukocytosis is usually healthy (e.g., fighting an

), but it also may be dysfunctionally proliferative. Proliferative disorders of white blood cells can be classed as myeloproliferative neoplasm, myeloproliferative and lymphoproliferative disorders, lymphoproliferative. Some are

, but many are

. Another way to categorize disorders of white blood cells is wikt:qualitative#Adjective, qualitatively. There are various disorders in which the number of white blood cells is normal but the cells do not function normally. Neoplasia of white blood cells can be benign tumor, benign but is often malignancy, malignant. Of the various tumors of the hematopoietic and lymphoid tissues, tumors of the blood and lymph, cancers of white blood cells can be broadly classified as leukemias and lymphomas, although those categories overlap and are often grouped together.

Leukopenias

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.

Neutropenia

Neutropenia can be acquired characteristic, acquired or congenital disorder, intrinsic. A decrease in levels of neutrophils on lab tests is due to either decreased production of neutrophils or increased removal from the blood. * Medications – chemotherapy, sulfas or other antibiotics, phenothiazines, benzodiazepines, antithyroid medications, anticonvulsants, quinine, quinidine, indometacin, procainamide, thiazides * Radiation * Toxins – alcohol (drug), alcohol, benzenes * Intrinsic disorders – Fanconi syndrome, Fanconi's, Kostmann syndrome, Kostmann's, cyclic neutropenia, Chédiak–Higashi syndrome, Chédiak–Higashi * Immune dysfunction – connective tissue diseases, AIDS, rheumatoid arthritis * Blood cell dysfunction – megaloblastic anemia, myelodysplasia,Bone marrow failure, Bone marrow transplant, acute leukemia * Any major infection * Miscellaneous – starvation, hypersplenism 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. One severe consequence of neutropenia is that it can increase the risk of infection.

Lymphocytopenia

Defined as total lymphocyte count below 1.0 billion/L, the cells most commonly affected are CD4+ T cells. Like neutropenia, lymphocytopenia may be acquired or intrinsic and there are many causes. This is not a complete list. * Inherited immune deficiency – severe combined immunodeficiency, common variable immunodeficiency, ataxia–telangiectasia, Wiskott–Aldrich syndrome, immunodeficiency with short-limbed dwarfism, Thymoma with immunodeficiency, immunodeficiency with thymoma, purine nucleoside phosphorylase deficiency, genetic polymorphism * Blood cell dysfunction – aplastic anemia * Infectious diseases – virus, viral (AIDS, SARS, West Nile encephalitis, hepatitis, herpes, measles, others), bacterial (tuberculosis, TB, typhoid, pneumonia, rickettsiosis, ehrlichiosis, sepsis), parasitic (acute phase of malaria) * Medications – chemotherapy (antilymphocyte globulin therapy, alemtuzumab, glucocorticoids) * Radiation * Major surgery * Miscellaneous – ECMO, kidney or bone marrow transplant, hemodialysis, kidney failure, severe burns, celiac disease, severe acute pancreatitis, sarcoidosis, protein-losing enteropathy, strenuous exercise, carcinoma * Immune dysfunction – arthritis, systemic lupus erythematosus, Sjögren syndrome, myasthenia gravis, systemic vasculitis, Behçet's disease, Behçet's-like syndrome, dermatomyositis, granulomatosis with polyangiitis * Nutritional/Dietary – alcohol use disorder, zinc deficiency Like neutropenia, symptoms and treatment of lymphocytopenia are directed at the underlying cause of the change in cell counts.

Proliferative disorders

An increase in the number of white blood cells in circulatory system, circulation is called

. This increase is most commonly caused by inflammation. 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. Leukocytosis may affect one or more cell lines and can be neutrophilic, eosinophilic, basophilic, monocytosis, or lymphocytosis.

Neutrophilia

Neutrophilia is an increase in the absolute neutrophil count in the systemic circulation, peripheral circulation. Normal blood values vary by age. 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. Primary causes * Conditions with normally functioning neutrophils – hereditary neutrophilia, chronic idiopathic neutrophilia * Pelger–Huët anomaly * Down syndrome * Leukocyte adhesion deficiency * Familial cold urticaria * Leukemia (chronic myelogenous leukemia, chronic myelogenous (CML)) and other myeloproliferative disorders * splenectomy, Surgical removal of spleen Secondary causes * Infection * Chronic inflammation – especially juvenile idiopathic arthritis, rheumatoid arthritis, Adult-onset Still's disease, Still's disease, Crohn's disease, ulcerative colitis, granulomatous infections (for example, tuberculosis), and chronic hepatitis * Cigarette smoking – occurs in 25–50% of chronic smokers and can last up to 5 years after quitting * Stress – exercise, surgery, general stress * Medication induced – glucocorticoids, corticosteroids (for example, prednisone, β-agonists, lithium) * Cancer – either by growth factors secreted by the tumor or invasion of bone marrow by the cancer * Increased destruction of cells in systemic circulation, peripheral circulation can stimulate bone marrow. This can occur in hemolytic anemia and idiopathic thrombocytopenic purpura

Eosinophilia

A normal eosinophil count is considered to be less than 0.65/L. 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. 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.

Counting and reference ranges

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. The normal total leucocyte count in an adult is 4000 to 11,000 per mm³ of blood. Differential leucocyte count: number/ (%) of different types of leucocytes per cubic mm. of blood. Below are reference ranges for various types leucocytes.Specific references are found in article Reference ranges for blood tests#White blood cells 2.

References

External links

Atlas of Hematology
* {{DEFAULTSORT:White Blood Cell Leukocytes, Blood Human cells Immune system Immunology Blood cells