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Medical conditions causing leukopenia
Low white cell counts may be due to a recent infection such as a cold or influenza. It can also be associated with chemotherapy, radiation therapy, myelofibrosis and aplastic anemia (failure of white and red cell creation, along with poor platelet production). HIV and AIDS are also a threat to white cells.
Other causes of low white blood cell count include systemic lupus erythematosus, Hodgkin's lymphoma, some types of cancer, typhoid, malaria, tuberculosis, dengue, rickettsial infections, enlargement of the spleen, folate deficiencies, psittacosis and sepsis. Many other causes exist, such as a deficiency in certain minerals, such as copper and zinc.
Pseudoleukopenia can develop upon the onset of infection. The leukocytes (predominately neutrophils, responding to injury first) are marginalized in the blood vessels so they can scan for the site of infection. This means increased WBC production will appear as though it is low from a blood sample, since the blood sample is of core blood and does not include the marginalized leukocytes.
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Non-deliberate immunosuppression
Further information: Immunodeficiency
Non-deliberate immunosuppression can occur in, for example, malnutrition, aging, many types ofcancer (such as leukemia, lymphoma, multiple myeloma), and certain chronic infections such asacquired immunodeficiency syndrome (AIDS).[1] The unwanted effect in non-deliberate immunosuppression is immunodeficiency that results in increased susceptibility to pathogens such as bacteria and virus.
Immunodeficiency is also a potential adverse effects of many immunosuppressant drugs. In this sense, the scope of the term immunosuppression in general includes both beneficial and potential adverse effects of decreasing the function of the immune system, whereas the termimmunodeficiency in general refers solely to the adverse effect of increased risk for infection.
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From Wikipedia, the free encyclopedia
| Leukopenia | |
|---|---|
| Classification and external resources | |
| ICD-10 | D70 |
| ICD-9 | 288.50 |
| DiseasesDB | 32396 |
| MeSH | D007970 |
Leukopenia (also known as leukocytopenia, orleucopenia, from Greek λευκό - white and πενία -deficiency) is a decrease in the number of white blood cells (leukocytes) found in the blood, which places individuals at increased risk of infection.
Neutropenia, a subtype of leukopenia, refers to a decrease in the number of circulating neutrophil granulocytes, the most abundant white blood cells. The terms leukopenia and neutropenia may occasionally be used interchangeably, as the neutrophil count is the most important indicator of infection risk.
Medication causing leukopenia
Some medications can have an impact on the number and function of white blood cells. Leukopenia is the reduction in the number of white blood cells, which may affect the overall white cell count or one of the specific populations of white blood cells. For example, if the number of neutrophils is low, the condition is known as neutropenia. Likewise, low lymphocyte levels are termed lymphopenia. Medications that can cause leukopenia include clozapine, an antipsychotic medication with a rare adverse effect leading to the total absence of all granulocytes (neutrophils, basophils, eosinophils). Other medications include immunosuppressive drugs, such as sirolimus, mycophenolate mofetil,tacrolimus, and cyclosporine. Interferons used to treat multiple sclerosis, like Rebif, Avonex, andBetaseron, can also cause leukopenia.
White blood cell
From Wikipedia, the free encyclopedia
"White Blood Cells" redirects here. For the album by The White Stripes, see White Blood Cells (album).
| White blood cell | |
|---|---|
 | |
| A scanning electron microscope image of normal circulating human blood. In addition to the irregularly shaped leukocytes, both red blood cells and many small disc-shapedplatelets are visible. | |
| Latin | leucocytus |
| Code | TH H2.00.04.1.02001 |
White blood cells, or leukocytes (also spelled "leucocytes"; from the Greek word leuko- meaning "white"), are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five[1] different and diverse types of leukocytes exist, but they are all produced and derived from a multipotentcell in the bone marrow known as a hematopoietic stem cell. They live for about three to four days in the average human body. Leukocytes are found throughout the body, including the blood andlymphatic system.[2]
The number of leukocytes in the blood is often an indicator of disease. There are normally between 4×109 and 1.1×1010 white blood cells in a litre of blood, and ranging from 7 and 21 micrometres in diameter, they make up approximately 1% of blood in a healthy adult.[3] An increase in the number of leukocytes over the upper limits is calledleukocytosis, and a decrease below the lower limit is called leukopenia. The physical properties of leukocytes, such as volume, conductivity, andgranularity, may change due to activation, the presence of immature cells, or the presence ofmalignant leukocytes in leukemia.
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[edit]Etymology
The name "white blood cell" derives from the fact that after centrifugation of a blood sample, the white cells are found in the buffy coat, a thin, typically white layer of nucleated cells between the sedimented red blood cells and the blood plasma. The scientific term leukocyte directly reflects this description, derived from Ancient Greek λευκό (white), and κύτταρο (cell). Blood plasma may sometimes be green if there are large amounts of neutrophils in the sample, due to the heme-containing enzyme myeloperoxidase that they produce.
[edit]Types
There are several different types of white blood cells. They all have many things in common, but are all distinct in form and function. A major distinguishing feature of some leukocytes is the presence of granules; white blood cells are often characterized as granulocytes or agranulocytes:
- Granulocytes (polymorphonuclear leukocytes): leukocytes characterised by the presence of differently staining granules in their cytoplasm when viewed under light microscopy. These granules are membrane-bound enzymes that act primarily in the digestion of endocytosedparticles. There are three types of granulocytes: neutrophils, basophils, and eosinophils, which are named according to their staining properties.
- Agranulocytes (mononuclear leukocytes): leukocytes characterized by the apparent absence ofgranules in their cytoplasm. Although the name implies a lack of granules these cells do contain non-specific azurophilic granules, which are lysosomes.[4] The cells include lymphocytes,monocytes, and macrophages.[5]
[edit]Overview table
 | This section may be confusing or unclear to readers. In particular,overview table lists 7 types, but other areas indicate 5 types. Also, macrophages and dendritic cells are derived/differentiated from monocytes, so there really are 5 main types. Please help clarify the section; suggestions may be found on the talk page. (September 2011) |
| Type | Microscopic Appearance | Diagram | Approx. % in adults[6] See also: Blood values | Diameter (μm)[6] | Main targets[3] | Nucleus[3] | Granules[3] | Lifetime[6] |
|---|---|---|---|---|---|---|---|---|
| Neutrophil |  |  | 54–62%[5] | 10–12 | multilobed | fine, faintly pink (H&E Stain) | 6 hours–few days (days inspleen and other tissue) | |
| Eosinophil |  |  | 1–6% | 10–12 |
| bi-lobed | full of pink-orange (H&E Stain) | 8–12 days (circulate for 4–5 hours) |
| Basophil |  |  | <1% | 12–15 |
| bi-lobedor tri-lobed | large blue | a few hours to a few days |
| Lymphocyte |  |  | 28–33% | 7–8 |
| deeply staining, eccentric | NK-cells and Cytotoxic (CD8+) T-cells | years for memory cells, weeks for all else. |
| Monocyte |  |  | 2–10% | 7.72–9.99[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 |
| Macrophage |  |  | 21 (human)[8] | Is a monocyte derivative.Phagocytosis(engulfment and digestion) of cellular debris andpathogens, and stimulation oflymphocytes and other immune cells that respond to the pathogen. | activated: days immune: months to years | |||
| Dendritic cells |  |  | Can be myeloid or lymphoid derived. Main function is as an antigen-presenting cell(APC) that activates T lymphocytes. | similar to macrophages |
[edit]Neutrophil
Main article: Neutrophil granulocyte
Neutrophils defend against bacterial or fungal infection and other very small inflammatory processes that 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 that may appear like multiple nuclei, hence the name polymorphonuclear leukocyte. The cytoplasm may look transparent because of fine granules that are pale lilac. Neutrophils are very 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, and make up 60-70% of total leukocyte count in human blood.[3] The life span of a circulating human neutrophil is about 5.4 days.[10]
[edit]Eosinophil
Main article: Eosinophil granulocyte
Eosinophils 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. In general, their nucleus is bi-lobed. The cytoplasm is full of granules that assume a characteristic pink-orange color with eosin stain.
[edit]Basophil
Main article: Basophil granulocyte
Basophils are chiefly responsible for allergic and antigen response by releasing the chemicalhistamine causing vasodilation. The nucleus is bi- or tri-lobed, but it is hard to see because of the number of coarse granules that hide it. They are characterized by their large blue granules.
[edit]Lymphocyte
Main article: Lymphocyte
Lymphocytes are much more common in the lymphatic system. Lymphocytes are distinguished by having a deeply staining nucleus that may be eccentric in location, and a relatively small amount of cytoplasm. The blood has three types of lymphocytes:
- B cells make antibodies that bind to pathogens to enable their destruction.
- T cells:
- CD4+ helper T cells: T cells having co-receptor CD4 are known as CD4+ T cells. These cells bind antigen presented by antigen-presenting cells via T-cell receptor interacting with MHC II complex on APC. Helper T cells coordinate the immune response. In acute HIV infection, these T cells are the main index to identify the individual's immune system activity.
- CD8+ cytotoxic T cells: T cells having 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. All nucleated cells possess MHC I on its surface.
- γδ T cells possess an alternative T cell receptor as opposed to CD4+ and CD8+ αβ T cells and 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 have lost MHC I molecule, as they have been infected by a virus or have become cancerous.
[edit]Monocyte
Main article: Monocyte
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 recognized again and killed, or so that an antibody response may be mounted. Monocytes eventually leave the bloodstream to become tissue macrophages, which remove dead cell debris as well as attacking microorganisms. Neither of these can be dealt with effectively by the neutrophils. Unlike neutrophils, monocytes are able to replace their lysosomal contents and are thought to have a much longer active life. They have the kidney shaped nucleus and are typically agranulated. They also possess abundant cytoplasm.
Once monocytes move from the bloodstream out into the body tissues, they undergo changes (differentiate) allowing phagocytosis and are then known as macrophages.
[edit]Medication causing leukopenia
Some medications can have an impact on the number and function of white blood cells. Leukopenia is the reduction in the number of white blood cells, which may affect the overall white cell count or one of the specific populations of white blood cells. For example, if the number of neutrophils is low, the condition is known as neutropenia. Likewise, low lymphocyte levels are termed lymphopenia. Medications that can cause leukopenia include clozapine, an antipsychotic medication with a rare adverse effect leading to the total absence of all granulocytes (neutrophils, basophils, eosinophils). Other medications include immunosuppressive drugs, such as sirolimus, mycophenolate mofetil,tacrolimus, and cyclosporine. Interferons used to treat multiple sclerosis, like Rebif, Avonex, andBetaseron, can also cause leukopenia.
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