Reactive lymphocyte
Encyclopedia
Reactive lymphocytes are lymphocytes that become large as a result of antigen
stimulation. Typically they can be more than 30 µm
in diameter with varying size and shape.
The nucleus
of a reactive lymphocyte can be round, elliptic, indented, cleft or folded. The cytoplasm
is often abundant and can be basophilic
. Vacuoles and/or azurophilic granules
are also sometimes present. Most often the cytoplasm is gray, pale blue or deep blue in colour.
The distinctive cell associated with EBV or CMV is known as a "Downey cell", after Hal Downey
, who contributed to the characterization of it in 1923. It is sometimes erroneously called a "Downy cell".
, however, they can also be present as a result of drug reactions
(such as phenytoin
), immunisations, radiation
, hormonal causes
(such as stress
and Addison's disease
) as well as some auto-immune disorders (such as rheumatoid arthritis
).
Some pathogen
-related causes include:
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
stimulation. Typically they can be more than 30 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
in diameter with varying size and shape.
The nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
of a reactive lymphocyte can be round, elliptic, indented, cleft or folded. The cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
is often abundant and can be basophilic
Basophilic
Basophilic is a technical term used by histologists. It describes the microscopic appearance of cells and tissues, as seen down the microscope, after a histological section has been stained with a basic dye. The most common such dye is haematoxylin....
. Vacuoles and/or azurophilic granules
Azurophil
An azurophil is an object readily stained with an azure dye. Azurophils include certain cytoplasmic granules in white blood cells and hyperchromatin, imparting a burgundy or merlot coloration. Neutrophils in particular are known for containing azurophils loaded with a wide variety of...
are also sometimes present. Most often the cytoplasm is gray, pale blue or deep blue in colour.
The distinctive cell associated with EBV or CMV is known as a "Downey cell", after Hal Downey
Hal Downey
Hal Downey was an American hematologist.In 1923, he contributed to the characterization of reactive lymphocytes, which are sometimes called "Downey cells".-See also:* Allan Watt Downie...
, who contributed to the characterization of it in 1923. It is sometimes erroneously called a "Downy cell".
Causes
Reactive lymphocytes are usually associated with viral illnessesVirus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
, however, they can also be present as a result of drug reactions
Adverse drug reaction
An adverse drug reaction is an expression that describes harm associated with the use of given medications at a normal dosage. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs...
(such as phenytoin
Phenytoin
Phenytoin sodium is a commonly used antiepileptic. Phenytoin acts to suppress the abnormal brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage-gated sodium channels...
), immunisations, radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
, hormonal causes
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
(such as stress
Stress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...
and Addison's disease
Addison's disease
Addison’s disease is a rare, chronic endocrine disorder in which the adrenal glands do not produce sufficient steroid hormones...
) as well as some auto-immune disorders (such as rheumatoid arthritis
Rheumatoid arthritis
Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...
).
Some pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
-related causes include:
- Epstein-Barr virusEpstein-Barr virusThe Epstein–Barr virus , also called human herpesvirus 4 , is a virus of the herpes family and is one of the most common viruses in humans. It is best known as the cause of infectious mononucleosis...
- CytomegalovirusCytomegalovirusCytomegalovirus is a viral genus of the viral group known as Herpesviridae or herpesviruses. It is typically abbreviated as CMV: The species that infects humans is commonly known as human CMV or human herpesvirus-5 , and is the most studied of all cytomegaloviruses...
- Toxoplasma
- Treponema pallidumTreponema pallidumTreponema pallidum is a species of spirochaete bacterium with subspecies that cause treponemal diseases such as syphilis, bejel, pinta and yaws. The treponemes have a cytoplasmic and outer membrane...
(SyphilisSyphilisSyphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
) - Streptococcus agalactiaeStreptococcus agalactiaeStreptococcus agalactiae is a beta-hemolytic Gram-positive streptococcus.- Identification :The CAMP test is an important test for identification...
(Group B Streptococci), - Hepatitis CHepatitis CHepatitis C is an infectious disease primarily affecting the liver, caused by the hepatitis C virus . The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years...
- HantavirusHantavirusHantaviruses are negative sense RNA viruses in the Bunyaviridae family. Humans may be infected with hantaviruses through rodent bites, urine, saliva or contact with rodent waste products...
External links
- Review Article: The Atypical Lymphocyte- International Pediatrics Volume 18, No. 1; Michael W. Simon.
- Educational Commentary: Blood Cell Identification - American Society for Clinical PathologyAmerican Society for Clinical PathologyThe American Society for Clinical Pathology is a professional association based in Chicago, Illinois encompassing 130,000 pathologists and laboratory professionals....
article.